guide to concrete repair

Preface

This guide contains the expertise ofnumerous individuals who havedirectly assisted the author on manyconcrete repair projects or freelyshared their concrete repairknowledge whenever requested. Their substantial contributions to thepreparation of this guide areacknowledged and appreciated. Someof the material in this guide originatedin the various editions ofReclamation’s Concrete Manual. Theauthor edited, revised, or updated thisinformation for inclusion herein.

Individuals who have been especiallyhelpful to the author include James E.Backstrom, former Reclamationengineer, mentor, and friend,deceased; Edward M. Harboe, Reclamation engineer, retired; U.Marlin Cash, Reclamation technician,deceased; Dennis O. Arney,Reclamation technician, retired;G.W. DePuy, Reclamation engineer,former

supervisor and friend, retired; andKurt D. Mitchell, Reclamationtechnician. Dr. Dave Harris,Manager, Materials Engineering andResearch Laboratory, obtained muchof the funding to prepare this guide;Kurt F. Von Fay, Civil Engineer,Materials Engineering and ResearchLaboratories, performed the peerreview; James E. McDonald,Structures Laboratory, WaterwaysExperiment Station, U.S. Army Corpsof Engineers, provided editorialreviews of selected information andmany useful sug-gestions andparticipated with the author in severalcooperative Reclamation—U.S. Corpsof Engineers concrete repair programs. The assistance of these and numerousother engineers and technicians isgratefully acknowledged.

i

Contents

Page

Chapter I—Repair of Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12. Maintenance of Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13. General Requirements for Quality Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Chapter II—A Concrete Repair System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4. Determine the Cause(s) of Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55. Evaluate the Extent of Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66. Evaluate the Need to Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77. Select the Repair Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88. Prepare the Old Concrete for Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89. Apply the Repair Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

10. Cure the Repair Properly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Chapter III—Causes of Damage to Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1911. Excess Concrete Mix Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1912. Faulty Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1913. Construction Defects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2214. Sulfate Deterioration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2315. Alkali-Aggregate Reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2316. Deterioration Caused by Cyclic Freezing and Thawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2417. Abrasion-Erosion Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2618. Cavitation Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2819. Corrosion of Reinforcing Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3420. Acid Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3521. Cracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3722. Structural Overloads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4123. Multiple Causes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Chapter IV—Standard Methods of Concrete Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4524. Surface Grinding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4525. Portland Cement Mortar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4526. Dry Pack and Epoxy-Bonded Dry Pack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4827. Preplaced Aggregate Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5028. Shotcrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5329. Replacement Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5730. Epoxy-Bonded Epoxy Mortar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6231. Epoxy-Bonded Replacement Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6932. Polymer Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7233. Thin Polymer Concrete Overlay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7434. Resin Injection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8035. High Molecular Weight Methacrylic Sealing Compound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8836. Polymer Surface Impregnation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9237. Silica Fume Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9238. Alkyl-Alkoxy Siloxane Sealing Compound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

ii

Page

Chapter V—Nonstandard Methods of Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9939. Use of Nonstandard Repair Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Appendix A

Figures

Figure Page

1 Lack of maintenance has resulted in near loss of this irrigation structure . . . . . . . . . . . . . . . . . . . . 22 Deferred maintenance has allowed freezing and thawing deterioration to

seriously damage this structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Freezing and thawing deterioration to the downstream face of this dam does

not require repair for safe operation of the structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 This freezing and thawing deterioration should have been repaired before it

advanced to the point that wall replacement or removal is the only option . . . . . . . . . . . . . . . . . . 95 Absorptive aggregate popout on a spillway floor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 Spillway damage requiring repairs at some future date . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 This concrete damage was found to be a serious threat to the structural integrity

of this spillway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 Saw cut patterns for the perimeters of repair areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 Corners of repair areas should be rounded whenever possible . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

10 Shot blasting equipment used to remove shallow concrete deterioration . . . . . . . . . . . . . . . . . . . . . 1411 Scrabbler equipment used to remove shallow concrete deterioration . . . . . . . . . . . . . . . . . . . . . . . . 1512 Multiple bits on the head of a scrabbler pound and pulverize the concrete surface

during the removal process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1613 Correct preparation of a concrete delamination. Perimeter has been sawcut to a

minimum depth of 1 inch, and concrete has been removed to at least 1 inch beneath exposed reinforcing steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

14 Preparation of a concrete deterioration that extends completely through a concrete wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

15 Preparation of a shallow defect on a highway bridge deck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1716 Relation between durability and water-cement ratio for air entrained and nonair-

entrained concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2017 Delamination caused by solar expansion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2218 Gel resulting from alkali-aggregate reaction causes expansion and tension cracks

in a concrete core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2419 Severe cracking caused by alkali-aggregate reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2520 Freezing and thawing deterioration on small irrigation gate structure . . . . . . . . . . . . . . . . . . . . . . . 2721 Freezing and thawing deterioration on spillway concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2722 D-cracking type of freezing and thawing deterioration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2823 Abrasion-erosion damage in a concrete stilling basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2924 Abrasion-erosion damage caused by sand or silt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2925 Early stages of abrasion-erosion damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3026 Placing silica fume concrete to repair a spillway floor damaged by cyclic freezing and

thawing and abrasion-erosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3127 Typical Christmas tree pattern of progressive cavitation damage . . . . . . . . . . . . . . . . . . . . . . . . . . . 3228 Extensive cavitation damage to Glen Canyon Dam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

iii

Figure Page

29 Concrete damage caused by chloride-induced corrosion of reinforcing steel. The waters contained within this flume had high chloride content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

30 Concrete deterioration caused by acidic water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3631 The depth of acidic water on this concrete wall is very apparent . . . . . . . . . . . . . . . . . . . . . . . . . . . 3632 Typical appearance of drying shrinkage cracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3833 Plastic shrinkage cracking caused by high evaporative water loss while the concrete

was still in a plastic state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3934 Inadequate crack repair techniques often result in poor appearance upon completion . . . . . . . . . . . 4035 Improper crack repair techniques often result in short service life . . . . . . . . . . . . . . . . . . . . . . . . . . 4036 Crack gage installed across a crack will allow determination of progressive widening

or movement of the crack. It may be necessary to monitor such gages for periods up to a year to predict future crack behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

37 A large reflective crack has formed in a concrete overlay which also exhibits circular drying shrinkage cracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

38 Multiple causes of damage are apparent in this photograph. Poor design or construction practices placed the electrical conduit too near the surface. A combination of freezing and thawing deterioration and alkali-aggregate reaction is responsible for the cracking and surface spalling on the parapet wall . . . . . . . . . . . . . . . . . . . . 44

39 A portland cement mortar patch seldom matches the color of the original concrete unless special efforts are taken to blend white cement with normal portland cement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

40 A small size pneumatic gun can be used to apply portland cement mortar. Regular shotcreting equipment would be too large for this application . . . . . . . . . . . . . . . . . . . . . 47

41 Saw-tooth bit used to cut slot for dry packing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4942 The downstream face of Barker Dam, near Boulder, Colorado, was resurfaced

with prepacked aggregate concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5143 Dry mix shotcrete equipment being used in the Denver concrete laboratories . . . . . . . . . . . . . . . . . 5444 Dry mix shotcrete equipment showing the nozzle and water injection ring . . . . . . . . . . . . . . . . . . . 5445 Wet mix shotcrete equipment. The premixed shotcrete is delivered to the

shotcrete pump by a transit truck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5546 Wet mix shotcrete is propelled by compressed air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5547 Preparation of a wall for placement of replacement concrete repairs . . . . . . . . . . . . . . . . . . . . . . . . 5948 Detail of forms for concrete replacement in walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6049 A gas-fired forced air heater is being used to heat concrete prior to

application of epoxy mortar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6450 An enclosure has been constructed over an area to be repaired with epoxy

mortar to keep the concrete warm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6651 A bucket mixer can be used to mix epoxy mortar for small repair areas . . . . . . . . . . . . . . . . . . . . . 6652 Epoxy mortar is consolidated and compacted by hand tamping . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6853 Applying the steel trowel finish required by epoxy mortar repairs . . . . . . . . . . . . . . . . . . . . . . . . . . 6854 Postcuring heating enclosure installed over an epoxy mortar repair area . . . . . . . . . . . . . . . . . . . . . 6955 If forms are required for epoxy-bonded concrete repairs, they should be installed at

least once prior to application of the epoxy bond coat to ensure that they fit as planned and that they can be installed and filled before the bond coat hardens . . . . . . . . . . . . . . 71

56 The placement techniques for epoxy-bonded concrete are essentially the same as for conventional concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

57 Placing polymer concrete in a repair area. Sandbags and polyethylene sheeting were used to prevent water from entering the repair area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

58 Small stinger vibrators can be used to consolidate shallow depths of polymer concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

iv

Figure Page

59 Polymer concrete must be protected from water and not disturbed during the 1- to 2-hour curing period. No other curing procedures are required unless ambient temperatures are very low . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

60 The thin PC overlay system may be applied with push brooms, squeegees, or heavy industrial grade paint rollers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

61 The thin PC overlay system can be applied very quickly. Two workmen completed application to this powerplant roof in 2 days . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

62 Proprietary epoxy injection equipment. Such equipment does not mix with resin components until the point of injection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

63 Commercial polyurethane injection pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8464 This is an air-powered pump system used for large scale polyurethane

resin injection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8565 An injection port with zirc fitting and a valved wall spear are shown in this

photograph. The wall spear can be used to relieve water pressure and to inject resin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

66 Several different types of injection port are shown in this photograph . . . . . . . . . . . . . . . . . . . . . . . 8867 A proprietary downhole packer allows separation of the resin components

until they reach the downhole point of injection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8968 High molecular weight methacrylic sealing compound is being applied to the

crest of Kortes Dam, near Casper, Wyoming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9069 This workman is hand screeding a small silica fume concrete repair . . . . . . . . . . . . . . . . . . . . . . . . 9570 Using a bull float on a silica fume concrete repair. Finishing must be done

immediately after screeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9571 Curing compound and polyethylene sheeting should be applied to cure silica fume

concrete as soon as finishing is completed if drying shrinkage cracking is to be prevented . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

72 A paint roller application of siloxane sealing compound to the downstream face of Nambe Falls Dam, near Sante Fe, New Mexico . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

1

Chapter I

Repair of Concrete

1. Introduction.—For many years, the Bureauof Reclamation (Reclamation) has published theConcrete Manual, the first edition dated July1938, and more recently, the StandardSpecifications For Repair of Concrete, M-47,the first edition dated November 1970. Thesubsequent revisions of these two documents(Bureau of Reclamation, 1975 and 1996),particularly chapter 7 of the Concrete Manual,have formed the basis for nearly all concreterepair performed on Reclamation projectsduring the past 25 years.

Reclamation operates and maintains a waterresources infrastructure, located primarily in theharsh climatic zones of the Western UnitedStates, valued at over $17 billion. It hasbecome apparent that there is need formodernization and expansion of the informationon the methods, materials, and procedures ofconcrete repair originally found in chapter 7 ofthe Concrete Manual. This Guide to Concrete Repair results fromrecognition of that need. It is designed to serveas a companion document to the "StandardSpecifications for Repair of Concrete" includedin appendix A of this guide.

This guide first discusses Reclamation'smethodology for concrete repair. It thenaddresses the more common causes of damageto Reclamation concrete, including suggestionsof the types of repair methods and materialsmost likely to be successful in repairingconcrete damage resulting from those causes. Finally, the guide contains a detaileddescription of the uses, limitations, materials,and procedures of each of the standard repairmethods/materials included in the "StandardSpecifications for Repair of Concrete."

2. Maintenance of Concrete.—Modernconcrete is a very durable construction materialand, if properly proportioned and placed, willgive very long service under normal conditions. Many Reclamation concrete structures,however, were constructed using early concretetechnology, and they have already provided wellover 50 years of service under harsh conditions. Such concrete must be inspected regularly toensure that it is receiving the maintenancenecessary to retain serviceability. Managersand foremen of operation and maintenancecrews must understand that, with respect toconcrete, there is no such thing as economicaldeferred maintenance. Failure to promptlyprovide the proper necessary maintenance willsimply result in very expensive repairs orreplacement of otherwise useful structures. Figures 1 and 2 demonstrate the folly ofinadequate or inappropriate maintenance. These two structures now require replacementat a cost tens of times greater than that of thepreventive maintenance that could haveextended their serviceability indefinitely.

Experience has shown that there are certainportions of exposed concrete structures morevulnerable than others to deterioration fromweathering in freezing climates. These areexposed surfaces of the top 2 feet of walls,piers, posts, handrails, and parapets; all ofcurbs, sills, ledges, copings, cornices, andcorners; and surfaces in contact with spray orwater at frequently changing levels duringfreezing weather. The durability of thesesurfaces can be considerably improved andserviceability greatly prolonged by preventivemaintenance such as weatherproofing treatmentwith concrete sealing compounds (sections 35and 38).

Guide to Concrete Repair

2

Figure 2.—Deferred maintenance has allowed freezing and thawing deteriorationto seriously damage this structure.

Figure 1.—Lack of maintenance has resulted in near loss of this irrigation structure.

Repair of Concrete

3

Selecting the most satisfactory protectivetreatment depends to a considerable extent uponcorrectly assessing the exposure environment. Concrete sealing compounds and coatings thatprovide good protection from weathering in anessentially dry environment may perform poorlyin the presence of an abundance of water suchas on some bridge curbs and railings, stillingbasin walls, and piers. Freezing and thawingtests of concrete specimens protected by avariety of concrete sealing compounds andcoatings, including linseed oil, fluosilicates,epoxy and latex paints, chlorinated rubber, andwater-proofing and penetrating sealers, havebeen performed in Reclamation laboratories.These tests indicate that proprietary epoxyformulations, siloxane and silane formulations,and the high molecular weight methacrylateformulations (section 35) clearly excel inresisting deterioration caused by repeatedfreezing and thawing in the presence of water. None of these formulations, however, willtotally "waterproof" concrete. That is, they willnot prevent treated concrete from absorbingwater and becoming saturated under conditionsof complete and long-term submergence.

The performance of new concrete sealingcompounds is continually being evaluated bythe Materials Engineering and ResearchLaboratory, Code D-8180, located in Denver,Colorado. If use of these materials is beingconsidered, the project should contact theDenver Office for the latest recommendationson materials, methods of mixing, application,curing, and precautions to be exercised duringplacement.

Except for hand-placed mortar restorations ofdeteriorated concrete (section 25), concretesealing compounds are ordinarily not applied onnew concrete construction. The treatments aremost commonly used on older surfaces whenthe earliest visible evidence of weather-ingappears. That is, the treatment is best usedbefore deterioration advances to a stage where itcannot be arrested. Such early evidenceconsists primarily of fine surface cracking, closeand parallel to edges and corners. The need forprotection also may be indicated by pattern

cracking, surface scaling or spalling, andshrinkage cracking. By treatment of thesevulnerable surfaces in the early stages ofdeterioration, later repairs may be avoided or atleast postponed for a long time.

Linseed oil-turpentine-paint preparations havebeen widely used in the past by Reclamation toretard concrete deterioration caused byweathering. These preparations, when appliedcorrectly, have been effective. The terminology"linseed oil treatment," however, has causedmany users to believe that a simple coating ofboiled linseed oil would protect concrete fromweathering. Such is not the case. The treatmentrecommended by Reclamation consisted of anumber of steps including acid washing surfacepreparation, 48-hour drying, and application oftwo or more coats of a hot linseed oil-turpentinemixture followed by two or more coats of whitelead paint, the first of which was thinned withlinseed oil and turpentine. The modernconcrete sealing compounds are much simplerto apply and provide superior protection to theconcrete. The use of the linseed oil-turpentine-oil paint system is no longer recommended.

3. General Requirements for QualityRepair.—The term "concrete repair" refers toany replacing, restoring, or renewing ofconcrete or concrete surfaces after initialplacement. The need for repairs can vary fromsuch minor imperfections as she-bolt holes,snap-tie holes, or normal weathering to majordamages resulting from water energy orstructural failure. Although the proceduresdescribed may initially appear to beunnecessarily detailed, experience hasrepeatedly demonstrated that no step in a repairoperation can be omitted or carelesslyperformed without detriment to theserviceability of the work. Inadequateworkmanship, procedures, or materials willresult in inferior repairs which will ultimatelyfail at significant cost.

(a) Workmanship.—It is the obligation of theconstruction contractor or operation andmaintenance crew to repair imperfections ordamage in concrete so that repairs will be


4

serviceable and of a quality and durabilitycomparable to the adjacent portions of thestructure. Repair personnel are responsible formaking repairs that are inconspicuous, durable,and well bonded to existing surfaces. Sincemost repair procedures involve predominantlymanual operations, it is particularly importantthat both foremen and workmen be fullyinstructed concerning procedural details ofrepairing concrete and the reasons for theprocedures. Workmen should also be apprizedof the more critical aspects of repairingconcrete. Constant vigilance must be exercisedby the contractor's and/or the Government'sforces to ensure maintenance of the necessarystandards of workmanship. Employment ofdependable and capable workmen is essential. Well trained, competent workmen areparticularly essential when epoxy, polyurethane,or other resinous materials are used in repair ofconcrete.

(b) Procedures.—Serviceable concrete repairscan result only if correct methods are chosenand techniques are carefully performed. Wrongor ineffective repair or construction procedures,coupled with poor workmanship, lead to inferiorrepairs. Many proven procedures for makinghigh quality repairs are detailed in this guide;however, not all procedures used in repair ormaintenance are discussed. Therefore, it isincumbent upon the craftsmen doing the workto use procedures that have been successful orthat have a proven high reliability factor.

Repairs made on new or old concrete should bemade as soon as possible after such need isrealized and evaluated. On new work, therepairs that will develop the best bond and,thus, are the most likely to be as durable andpermanent as the original work are those thatare made immediately after stripping of theforms while the concrete is quite green. For thisreason, repairs to newly constructed concreteshould be completed within 24 hours after theforms have been removed.

Before repairs are commenced, the method andmaterials proposed for use should be approvedby an authorized inspector. Routine curing

should be interrupted only in the area of repairoperations.

Effective repair of deteriorated portions ofconcrete structures cannot be ensured unlessthere is complete removal of all deteriorated orpossibly affected concrete, careful replacementin strict accordance with a standard or approvedprocedure, and assurance of secure anchorageand effective drainage when needed. Consequently, work of this type should not beundertaken unless or until ample time,personnel, and facilities are available. Only asmuch of this work should be undertaken as canbe completed correctly; otherwise, the workshould be postponed, but not so long as to allowfurther deterioration. Repairs should be made atthe earliest possible date.

(c) Materials.—Materials to be used in concreterepair must be high quality, relatively fresh, andcapable of meeting specifications requirementsfor the particular application or intended use. Mill reports or testing laboratory reports shouldbe required of the supplier or manufacturer asan indication of quality and suitability. Short ofthis requirement, certifications stating that thematerials meet certain specifications should berequired of the supplier. Due to the high costassociated with the subsequent removal andreplacement of new, unknown, or unprovenmaterials if they prove unsuitable for the job,such materials should never be used in concreterepair unless (1) the standard repair materialshave been determined unsuitable and (2) theowners and all other parties to the repair havebeen informed of the need to use nonstandardmaterials and the associated risk.

Materials selected for repair application must beused in accordance with manufacturers'recommendations or other approved methods.Mixing, proportioning, and handling must be inaccordance with the highest standards ofworkmanship.

5

Chapter II

A Concrete Repair System

Concrete repairs have occurred on Reclamationprojects since the first construction concretewas placed in 1903. Unfortunately, eventhough the best available materials were used,many repair failures have occurred during the90 years since that first concrete construction. In evaluating the causes of these failures, it waslearned that it is essential to consistently use asystematic approach to concrete repair. Thereare several such repair approaches or systemscurrently in use. The U.S. Army Corps ofEngineers lists an excellent system in the firstchapter of its manual, Evaluation and Repair ofConcrete Structures (U.S. Army Corps ofEngineers, 1995). Other organizations, such asthe American Concrete Institute, the PortlandCement Association, the International ConcreteRepair Institute, and private authors (Emmons,1994) have also published excellentmethodologies for concrete repair. This guidewill not attempt to discuss or evaluate thesesystems for any particular set of fieldconditions. Rather, the following seven-steprepair system, which has been developed, used,and evaluated by Reclamation over an extendedperiod of time, is presented. This methodologyhas been found suitable for repairingconstruction defects in newly constructedconcrete as well as old concrete that has beendamaged by long exposure and service underfield conditions.

This system will be found most useful iffollowed in a numerically sequential, or stepwise manner. Quite often, the first questionsasked when the existence of deteriorated ordamaged concrete becomes apparent are: "Whatshould be used to repair this?" and "How muchis this going to cost?". These are not improperquestions. However, they are questions askedat an improper time. Ultimately, thesequestions must be answered, but pursuinganswers to these questions too early in the

repair process will lead to incorrect and, therefore,extremely costly solutions. If a systematicapproach to repair is used, such questions will beasked when sufficient information has beendeveloped to provide correct and economicalanswers.

Reclamation's Concrete Repair System

1. Determine the cause(s) of damage2. Evaluate the extent of damage3. Evaluate the need to repair4. Select the repair method5. Prepare the old concrete for repair6. Apply the repair method7. Cure the repair properly

4. Determine the Cause(s) of Damage.— Thefirst and often most important step of repairingdamaged or deteriorated concrete is to correctlydetermine the cause of the damage. If the cause ofthe original damage to concrete is not determinedand eliminated, or if an incorrect determination ismade, whatever damaged the original concrete willlikely also damage the repaired concrete. Moneyand effort spent for such repairs is, thus, totallywasted. Additionally, larger and even more costlyreplacement repairs will then be required.

If the original damage is the result of a one- timeevent, such as a river barge hitting a bridge pier, anearthquake, or structural overload, remediation ofthe cause of damage need not be addressed. It isunlikely that such an event will occur again. If,however, the cause of damage is of a continuing orrecurring nature, remediation must be addressed, orthe repair method and materials must in somemanner be made resistant to predictable futuredamage. The more common causes of damage toReclamation concrete are discussed in chapter III. A quick review of these common causes of damagereveals that the majority of them are of acontinuing or recurring nature.


6

It is important to differentiate between causes ofdamage and symptoms of damage. In the abovecase of the river barge hitting the bridge pier,the cause of damage is the impact to theconcrete. The resultant cracking is a symptomof that impact. In the event of freezing andthawing deterioration to modern concrete, thecause of the damage may well lie with the useof low quality or dirty fine or coarse aggregatein the concrete mix. The resultant scaling andcracking is a symptom of low durabilityconcrete. The application of high cost repairs tolow quality concrete is usually economicallyquestionable.

It is somewhat common to find that multiplecauses of damage exist (section 23). Improperdesign, low quality materials, or poorconstruction practices reduce the durability ofconcrete and increase its susceptibility todeterioration from other causes. Similarly,sulfate and alkali-silica deterioration causecracks in the exterior surfaces of concrete thatallow accelerated deterioration from cycles offreezing and thawing. The deteriorationresulting from the lowered resistance to cyclicfreezing and thawing might mask the originalcause of the damage.

Finally, it is important to fully understand theoriginal design intent and concepts of adamaged structure before attempting repair. Low quality local aggregate may haveintentionally been used in the concrete mixbecause the costs associated with hauling higherquality aggregate great distances may havemade it more economical to repair the structurewhen required at some future date. A classicexample of misunderstanding the intent ofdesign recently occurred on a project inNebraska. A concrete sluiceway that wouldexperience great quantities of waterborne sandwas designed with an abrasion-resistantprotective overlay of silica fume concrete. Thisoverlay was intentionally designed so that itwould not bond to the base concrete, makingreplacement easier when required by theanticipated abrasion-erosion damage. Thisdesign concept, however, was notcommunicated to construction personnel who

became deeply concerned when the silica fumeoverlay was found to be "disbonded" shortly afterplacement and curing was completed. Somedifficulty was experienced in preventing fieldpersonnel from requiring the constructioncontractor to repair a perfectly serviceableoverlay that was performing exactly as intended.

5. Evaluate the Extent of Damage.—The nextstep of the repair process is to evaluate the extentand severity of damage. The intent of this step isto determine how much concrete has beendamaged and how this damage will affectserviceability of the structure (how long, howwide, how deep, and how much of the structureis involved). This activity includes prediction ofhow quickly the damage is occurring and whatprogression of the damage is likely.

The importance of determining the severity ofthe damage should be understood. Damageresulting from cyclic freezing and thawing,sulfate exposure, and alkali-aggregate reactionappears quite similar. The damage caused byalkali-aggregate reaction and sulfates is far moresevere than that caused by freeze-thaw, althoughall three of these causes can result in destructionof the concrete and loss of the affected structure. The main difference in severity lies in the factthat proper maintenance can reduce or eliminatedamage caused by freeze-thaw. There is noproven method of reducing damage caused byalkali-aggregate reaction or sulfate exposure.

The most common technique used to determinethe extent of damage is sounding the damagedand surrounding undamaged concrete with ahammer. If performed by experienced personnel,this simple technique, when combined with aclose visual inspection, will provide the neededinformation in many instances of concretedamage. In sounding suspected delaminated ordisbonded concrete, it should be rememberedthat deep delaminations or delaminations thatcontain only minute separation may not alwayssound drummy or hollow. The presence of suchdelaminations can be detected by placing a handclose to the location of hammer blows or byclosely observing sand particles on the surface


7

close to the hammer blows. If the hand feelsvibration in the concrete, or if the sand particlesare seen to bounce however slightly due to thehammer blows, the concrete is delaminated.

An indication of the strength of concrete canalso be determined by hammer blows. Highstrength concrete develops a distinct ring from ahammer blow and the hammer reboundssmartly. Low strength concrete resounds with adull thud and little rebound of the hammer. More detailed information can be obtained byusing commercially available reboundhammers, such as the Schmidt ReboundHammer.

Cores taken from the damaged areas can beused to detect subsurface deterioration, todetermine strength properties throughlaboratory testing, and to determinepetrography. Petrographic examination ofconcrete obtained by coring can also be veryuseful in determining some causes ofdeterioration.

There are a number of nondestructive testingmethods that can be used to evaluate the extentof damage (Poston et al., 1995). The above-mentioned Schmidt Rebound Hammer isperhaps the cheapest and simplest to use. Ultrasonic pulse velocity and acoustic pulseecho devices measure the time required for anelectronically generated sound wave to eithertravel through a concrete section or to travel tothe far side of a concrete section and rebound. Damaged or low quality concrete deflects orattenuates such sound waves and can bedetected by comparison of the resulting traveltime with that of sound concrete. Acousticemission devices detect the elastic waves thatare generated when materials are stressed orstrained beyond their elastic limits. With suchdevices, it is possible to "hear" the impulsesfrom development of microcracks in overlystressed concrete. Acoustic emissionequipment has been used to "hear" theoccurrence of prestressing strand failure in largediameter prestressed concrete pipe. Withcomputer assistance, several acoustic emissiondevices have been used not only to detect the

occurrence of strand failure(s), but throughtriangulation, they were able to determine thelocation of the failure(s) (Travers, 1994).

The areas of deteriorated or damaged concretediscovered by these methods should be mappedor marked on drawings of the affected structureto provide information needed in subsequentcalculations of the area and volume of concreteto be repaired and for preparation of repairspecifications. Even though care is taken inthese investigations, it is common to find duringpreparation of the concrete for repair that theactual area and volume of deteriorated concreteexceeds the original estimate. For this reason, itis usually a good idea to increase the computedquantity estimates by 15 to 25 percent to coveranticipated overruns.

6. Evaluate the Need to Repair.—Not alldamaged concrete requires immediate repair. Many factors need consideration before thedecision to perform repairs can be made. Obviously, repair is required if the damageaffects the safety or safe operation of thestructure. Similarly, repairs should be performedif the deterioration has reached a state, or isprogressing at a rate, such that futureserviceability of the structure will be reduced. Most concrete damage, however, progressesslowly, and several options are usually availableif the deterioration is detected early. With earlydetection, it may be possible to arrest the rate ofdeterioration using maintenance procedures. Even if repair is required, early detection ofdamage will allow orderly budgeting of funds topay the costs of repair.

Some types of concrete deterioration can simplybe ignored. Cracking due to drying shrinkageand freezing and thawing deterioration iscommon on the downstream face of many olderwestern dams. These types of damage areunsightly, but repair can seldom be justified forother than cosmetic purposes. It should beanticipated that such repairs might be moreunsightly and of lower durability than theexisting concrete. Conversely, structural cracksdue to foundation settlement and freezing andthawing deterioration to the walls or floor of a


8

spillway will usually require repair, if notimmediately, at some point in the future. Figure3 shows freezing and thawing damage to theface of a dam that does not require repair forsafe operation of the structure. Figure 4 showssimilar damage that should have been repairedlong ago. Damage caused by absorptiveaggregate popouts is common on bridge deck,canal, and dam concrete (figure 5). Unless suchconcrete is exposed to high velocity waterflows,where the offsets caused by popouts can resultin cavitation damage, repair can be ignored. Figure 6 shows damage to a spillway thatappears quite serious, and repair is obviouslyrequired. This spillway, however, isconstructed with a very thick slab and does notexperience high velocity water flow. Therepairs can be scheduled at some future date toallow an orderly process of budgeting to obtainthe required funding. It should be noted,however, that proper maintenance might haveeliminated the need to repair this spillway.

Selecting or scheduling the most optimum timeto perform needed concrete repair should bepart of the process of determining the need torepair. Except in emergencies, many irrigationstructures cannot be removed from serviceduring the water delivery season. The expenseor loss of income involved with the inopportunerelease of reservoir water in order to lowerwater surface elevations to accomplish repairsmay exceed the costs of the repairs by manytimes. If such costs exceed the value of thebenefits expected from performing repairs, itmight be prudent to postpone or even cancelperformance of the repairs. Figure 7 showsdamage on a spillway floor. This damage wasinitially judged to be of a nonserious nature. Closer evaluation, however, revealed thatfoundation material had been removed from avery large area beneath this floor slab and thatimmediate repair was required. Had thisspillway been operated without repair duringperiods of high spring runoff or floodflows,extensive additional damage might haveresulted.

These first steps—determining the cause ofdamage, evaluating the extent of damage, and

evaluating the need to repair—form the basis ofwhat is known as a condition survey. If thedamage is not extensive or if only a small part ofa structure is involved, the condition surveycould be simply a mental exercise. If majorrepair or rehabilitation is required, a detailedcondition survey should be performed anddocumented. Such a survey will consist ofreview of the plans, specifications, and operatingparameters for the structure; determination ofconcrete properties; and any additional fieldsurveys, engineering studies, or structuralanalysis required to fully evaluate the presentand desired conditions of the structure(American Concrete Institute, 1993). The finalfeature of a condition survey, completed onlyafter the above-listed items have been completed,is a list of the recommended repair methods andmaterials.

7. Select the Repair Method.—There is atendency to attempt selection of repairmethods/materials too early in the repair process. This should be guarded against. Withinsufficient information, it is very difficult tomake proper, economical, and successfulselections. Once the above three steps of therepair process have been completed, or uponcompletion of a detailed condition survey, theselection of proper repair methods and materialsusually becomes very easy. These steps definethe types of conditions the repair must resist, theavailable repair construction time period, andwhen repairs must be accomplished. Thisinformation, in combination with data on thevolume and area of concrete to be repaired, willusually determine which of the 15 standardrepair materials should be used. Also, thisinformation will determine when the standardrepair materials cannot be expected to performwell and when nonstandard materials should beconsidered (see chapter V). Chapter IV containsa detailed discussion of each of the standardrepair materials.

8. Prepare the Old Concrete for Repair.—Preparation of the old concrete for application ofthe repair material is of primary importance inthe accomplishment of durable repairs. The


9

Figure 4.—This freezing and thawing deterioration should have been repaired before it advanced to the point that wall replacement or removal is the only option.

Figure 3.—Freezing and thawing deterioration to the downstream face of this damdoes not require repair for safe operation of the structure.


10

Figure 5.—Absorptive aggregate popout on spillway floor.

Figure 6.—Spillway damage requiring repairs at some future date.


11

Figure 7.—This concretedamage was found to be aserious threat to thestructural integrity of thisspillway.

very best of repair materials will giveunsatisfactory performance if applied toweakened or deteriorated old concrete. Therepair material must able to bond to soundconcrete. It is essential that all of the unsoundor deteriorated concrete be removed before newrepair materials are applied.

Saw Cut Perimeters. The first step in pre-paring the old concrete for repair is to saw cutthe perimeter of the repair area to a depth of 1to 1.5 inches. The purpose of the saw cuts is toprovide a retaining boundary against which therepair material can be compacted andconsolidated. The perimeters of repairs are thelocations most exposed to the effects ofshrinkage, deterioration, and bond failure. Onlypoor compaction of repair material can beaccomplished at feather edge perimeters. Such

repair zones will fail quickly. For this reasonfeather edge perimeters to repair areas are notpermitted by Reclamation's M-47specifications. It is unnecessary to cut to thefull depth of the repair, although to do so is notharmful. The saw cuts should be perpendicularto the concrete surface or tilted inward 2 to 3degrees to provide retaining keyways thatmechanically lock the repair material into thearea. Tilting the saw inward more than 3degrees may result in weak top corners in theold concrete and should be avoided. The sawcuts should never be beveled outward.

It is usually false economy to try to closelyfollow the shape of the repair area with amultitude of short saw cuts as seen at thebottom of figure 8. The cost of sawing such ashape most likely will exceed the cost of


12

Figure 8.—Saw cut patterns for theperimeters of repair areas.

increased repair area, and the resulting repairmay be less attractive than those having simplerectangular shapes. Saw cuts should not meetin acute angles as shown at the top of figure 8. It is very difficult to compact repair materialinto such sharp corners. The saw cut perimetersshould have rounded corners, as seen in figure9, whenever reasonable. Rounded cornerscannot be cut with a circular concrete saw, butthe cuts can be stopped short of the intersectionand rounded using a jackhammer or bushhammer carefully held in a vertical orientation. It should be noted that intersections cannot becut with a circular saw without the cutsextending outside the intersection. These cutextensions often serve as sources of cracking insome repair materials. Once the perimetershave been cut, the deteriorated concrete isremoved using methods discussed in followingparagraphs.

Concrete Removal. All deteriorated ordamaged concrete must be removed from therepair area to provide sound concrete for therepair material to bond to. It is always falseeconomy to attempt to save time or money byshortchanging the removal of deterioratedconcrete. Whenever possible, the first choice ofconcrete removal technique should be highpressure (8,000 to 15,000 pounds per squareinch [psi]) hydroblasting or hydrodemolition. These techniques have the advantage ofremoving the unsound concrete while leavinghigh quality concrete in place. They have afurther advantage in that they do not leavemicrofractured surfaces on the old concrete. Impact removal techniques, such as bush-hammering, scrabbling, or jackhammering, canleave surfaces containing a multitude ofmicrofractures which seriously reduce the bondof the repair material to the existing


13

Figure 9.—Corners of repair areasshould be rounded whenever possible.

concrete. Subsequent removal of the micro-fractured surface by hydroblasting, shotblasting, or by wet or dry sandblasting isrequired by Reclamation's M-47 specificationsif impact removal techniques are used. Adisadvantage of the high pressure water blastingtechniques is that the waste water and debrismust be handled in an environmentallyacceptable manner as prescribed by localregulations.

Impact concrete removal techniques, such asjackhammering for large jobs and bush-hammering for smaller areas, have been usedfor many years. These removal procedures arequick and economical, but it should be kept inmind that the costs of subsequent removal of themicrofractured surfaces resulting from thesetechniques must be included when comparing

the costs of these techniques to the costs of highpressure water blasting. The maximum size ofjackhammers should usually be limited to 60pounds. The larger jackhammers removeconcrete at a high rate but are more likely todamage surrounding sound concrete. Thelarger hammers can impact and loosen the bondof concrete to reinforcing steel for quite somedistance away from the point of impact. Pointed hammer bits, which are more likely tobreak the concrete cleanly rather than topulverize it, should be used to reduce theoccurrence of surface microfracturing.

Shallow surface deterioration (usually less than1/2 inch deep) is best removed with shot blasting (figure 10) or dry or wet sand-blasting.Shot blasting equipment is highly efficient andusually includes some type of vacuum pickup of


14

Figure 10 – Shot blasting equipment used to remove shallow concrete deterioration


15

Figure 11.—Scrabbler equipment used to remove shallow concrete deterioration.

the resulting dust and debris. The use of suchequipment is much more environmentallyacceptable than dry sand blasting. The need forremoval of such shallow depths of deterioratedconcrete is seldom encountered in Reclamationrepairs other than for removal of microfracturedsurfaces or for cosmetic surface cleaning. Shallow deterioration to concrete surfaces canalso be removed with tools known as scrabblers(figure 11). These tools usually have multiplebits (figure 12) which pound and pulverize theconcrete surfaces in the removal process. Theiruse greatly multiplies the micro fractures in theremaining concrete surfaces. Extensive highpressure water, sand, or shot blasting efforts arethen needed to remove the resulting damagedsurfaces. Such efforts are seldom attainedunder field conditions. For this reason,Reclamation's M-47 specifications prohibit useof scrabblers for concrete removal.

Reinforcing Steel Preparation. Reinforcingsteel exposed during concrete removal requiresspecial treatment. As a minimum, all scale,rust, corrosion, and bonded concrete must beremoved by wire brushing or high pressurewater or sand blasting. It is not necessary to

clean the steel to white metal condition, just toremove all the loose or poorly bonded debristhat would affect bond between the repairmaterial and the reinforcing steel. If corrosionhas reduced the cross section of the steel to lessthan 75 percent of its original diameter, theaffected bars should be removed and replacedin accordance with section 12.14 of American Concrete Institute (ACI) 318 (ACI, 1992). Steel exposed more than one-third of itsperimeter circumference should be sufficientlyexposed to provide a 1-inch minimum clearancebetween the steel and the concrete. Figure 13shows the correct concrete removal andpreparation for repairing a delamination occurring at the top mat of reinforcing steel of aconcrete slab. Figure 14 shows correctpreparation of a concrete defect that extendsentirely through a wall. Figure 15 shows aproperly prepared shallow repair area on ahighway bridge deck.

Maintenance of Prepared Area. After therepair area has been prepared, it must bemaintained in a clean condition and protected


16

Figure 12.—Multiple bits on the head of a scrabbler pound and pulverize theconcrete surface during the removal process.

.

Figure 13.—Correct preparation of a concrete delamination. Perimeter hasbeen saw cut to a minimum depth of 1 inch, and concrete has been

removed to at least 1 inch beneath exposed reinforcing steel.


17

Figure 14.—Preparation of a concrete deterioration that extends completelythrough a concrete wall.

Figure 15.—Preparation of a shallow defect on a highway bridge deck.


18

from damage until the repair materials can be placed and cured. In hot climates, this mightinvolve providing shade to keep the concretecool, thereby reducing rapid hydration orhardening. If winter conditions exist, stepsneed to be taken to provide sufficient insulationand/or heat to prevent the repair area frombeing covered with snow, ice, or snowmeltwater. It should be remembered that repairactivities can also contaminate or damage aproperly prepared site. Workmen placing repairmaterials in one area of a repair often trackmud, debris, cement dust, or concrete into anadjacent repair area. Once deposited on aprepared surface, this material will serve as abond breaker if not cleaned up before the newrepair material is placed. Repair contractorsshould be required to repeat preparation if arepair area is allowed to become damaged orcontaminated. The prepared concrete should bekept wet or dry, depending upon the repairmaterial to be used. Surfaces that will receivepolymer concrete or epoxy-bonded materialsshould be kept as dry as possible. Someepoxies will bond to wet concrete, but theyalways bond better to dry concrete. Surfacesthat will be repaired with cementitious materialshould be in a saturated surface dry (SSD)condition immediately prior to materialapplication. This condition is achieved bysoaking the surfaces with water for 2 to 24hours just before repair application. Immediately before material application, therepair surfaces should be blown free of water,using compressed air. The SSD conditionprevents the old concrete from absorbing mixwater from the repair material and promotesdevelopment of adequate bond strength in therepair material. The presence of free water onthe repair surfaces during application of therepair material must be avoided wheneverpracticable.

9. Apply the Repair Method.—There are15 different standard concrete repairmethods/materials in Reclamation's M-47specification. Each of these materials hasuniquely different requirements for successfulapplication. These requirements andapplication procedures are discussed at lengthin chapter IV of this guide.

10. Cure the Repair Properly.—All of thestandard repair materials, with the exception ofsome of the resinous systems, require propercuring procedures. Curing is usually the finalstep of the repair process, followed only bycleanup and demobilization, and it is somewhatcommon to find that the curing step has beenshortened, performed haphazardly, oreliminated entirely as a result of rushing toleave the job or for the sake of perceivedeconomies. It should be understood that propercuring does not represent unnecessary costs. Rather, it represents a sound investment inlong-term insurance. Inadequate or impropercuring can result in significant loss of money. At best, improper curing will reduce the servicelife of the repairs. More likely, inadequate orimproper curing will result in the necessity toremove and replace the repairs. The costs ofthe original repair are, thus, completely lost,and the costs of the replacement repair will begreater because the replacement repairs will belarger and must include the costs of removal ofthe failed repair material. The curingrequirements for each of the 15 standard repairmaterials are discussed in chapter IV.

19

Chapter III

Causes of Damage to Concrete

The more common causes of damage toReclamation concrete are discussed in thischapter. The discussion for each cause ofdamage consists of (1) a description of thecause and how it damages concrete and (2) adiscussion and/or listing of appropriatemethods/materials to repair that particular typeof concrete damage. The format for the text ofthis chapter was chosen in recognition of theimportance of first determining the cause(s) ofdamage to concrete before trying to select therepair method. It is expected that the fulldiscussion of the selected repair method, asfound in chapter IV, will be consulted prior toperformance of the work.

11. Excess Concrete Mix Water.—The use ofexcessive water in concrete mixtures is thesingle most common cause of damage toconcrete. Excessive water reduces strength,increases curing and drying shrinkage, increasesporosity, increases creep, and reduces theabrasion resistance of concrete. Figure 16shows the cumulative effects of water-cementratio on the durability of concrete. In thisfigure, high durability is associated with lowwater-cement ratio and the use of entrained air.

Damage caused by excessive mix water can bedifficult to correctly diagnose because it isusually masked by damage from other causes. Freezing and thawing cracking, abrasionerosion deterioration, or drying shrinkagecracking, for example, is often blamed fordamage to concrete when, in reality, excessivemix water caused the low durability thatallowed these other causes to attack theconcrete. During petrographic examination,extreme cases of excessive mix water inhardened concrete can sometimes be detectedby the presence of bleed water channels orwater pockets under large aggregate. Morecommonly, examination of the batch sheets, mix

records, and field inspection reports willprovide confirmation of the use of excessivemix water in damaged concrete. It should berecognized, however, that water added to transittruck mixes at the construction site or applied to concrete surfaces during finishingoperations often goes undocumented.

The only permanent repair of concrete damagedby excessive mix water is removal andreplacement. However, depending on the extentand nature of damage, a number of maintenanceor repair methods can be useful in extending theservice life of such concrete. If the damage isdetected early and is shallow (less than 1.5inches deep), application of concrete sealingcompounds, such as the high solids content(greater than 15 percent) oligomeric alkyl-alkoxy siloxane or silane systems (section 38) orthe high molecular weight methacrylicmonomer system (section 35), will reduce waterpenetration and improve resistance to freeze-thaw spalling and deterioration. Such systemsrequire reap-plication at 5- to 10-year intervals. Epoxy- bonded replacement concrete (section31) can be used to repair damage that extendsbetween 1.5 and 6 inches into the concrete, and replacement concrete (section 29) can beused to repair damage 6 inches deep or deeper.

12. Faulty Design.—Design faults can createmany types of concrete damage. Discussion ofall the types of damage that can result fromfaulty design is beyond the scope of this guide. However, one type of design fault that issomewhat common is positioning em-beddedmetal such as electrical conduits or outlet boxestoo near the exterior surfaces of concretestructures. Cracks form in the concrete overand around such metal features and allowaccelerated freeze-thaw deterioration to occur. Bases of handrails or guardrails


20

Figure 16.—Relation between durability and water-cement ratio for air entrained andnonair entrained concrete.


21

are placed too near the exterior corners of walls,walkways, and parapets with similar results. These bases or intrusions into the concreteexpand and contract with temperature changesat a rate different from the concrete. Tensilestresses, created in the concrete by expandingmetal, cause cracking and subsequent freeze-thaw damage. Long guardrails or handrails cancreate another problem. The pipe used for suchrails also undergoes thermal expansion andcontraction. If sufficient slip joints are notprovided in the rails, the expansion andcontraction cause cracking at the points wherethe rail attachment bases enter the concrete. This cracking also allows accelerated damage tothe concrete from freezing and thawing.

Insufficient concrete cover over reinforcingsteel is a common cause of damage to highwaybridge structures. This can also be a problem in hydroelectric and irrigationstructures. Reclamation usually requires aminimum of 3 inches of concrete cover overreinforcing steel, but in corrosive environments,this can be insufficient. Concrete exposed tothe corrosive effects of sulfates, acids, orchlorides should have a minimum of 4 inches ofcover to protect the reinforcing steel. Insufficient cover allows corrosion of thereinforcing steel to begin. The iron oxidebyproducts of this corrosion require more spacein the concrete than the reinforcing steel andresult in cracking and delaminating in theconcrete.

Failure to provide adequate contraction joints orfailure to make expansion joints wide enough toaccommodate temperature expansion inconcrete slabs will result in damage. Concretewith inadequate contraction joints will crackand make a joint wherever a joint was neededbut not pro-vided. Unfortunately, such crackswill not be as visually attractive as a formed orsawed joint. Formation of the cracks relievesthe tensile stresses and, though unsightly,seldom requires repair. Concrete slabsconstructed with insufficient or too narrowexpansion joints can cause serious damage tobridge deck surfaces, dam roadways, and thefloors

of long, steeply sloping, south facing spillways. Such concrete experiences large daily andseasonal temperature changes resulting fromsolar radiation. The resulting concreteexpansion is greater in the top surfaces of theslabs, where the concrete temperatures arehigher, and less in the cooler bottom edges. Such expansion can cause the upper portions ofconcrete in adjacent slabs to butt against oneanother at the joints between the slabs. Theonly possible direction of relief movement insuch slabs is upward, which causesdelaminations to form in the concrete, startingat the joints and extending an inch or two backinto the slab. These delaminations arecommonly located at the top mat of reinforcingsteel. In temperate climates, the formation ofdelaminations relieves the expansion strains,and further damage will usually cease. In coldclimates, however, water can enter thedelaminations where it undergoes a daily cycleof freezing and thawing. This causes thedelaminations to grow and extend as much as 3to 5 feet away from the joint. Figure 17 is anexaggerated example of such damage.

Repair of damage caused by faulty design isfutile until the design faults have beenmitigated. Embedded metal features can beremoved, handrails can be provided with slipjoints, and guardrail attachment bases can bemoved to locations with sufficient concrete towithstand the tensile forces. Mitigation ofinsufficient concrete cover over reinforcingsteel is very difficult, but repair materialsresistant to those particular types of corrosioncan be selected for the repair. Repairs can alsobe protected by concrete sealing compounds orcoatings to reduce water penetration. Slabscontaining inadequate expansion joints can besaw cut to increase the number of joints and/orto widen the joints to provide sufficient roomfor the expected thermal expansion.

Damage caused by design faults can most likelybe repaired using replacement concrete (section29), epoxy-bonded replacement concrete(section 31), or epoxy-bonded epoxy mortar(section 30).


22

Figure 17.—Delamination caused by solar expansion.

13. Construction Defects.—Some of the morecommon types of damage to concrete caused byconstruction defects are rock pockets andhoneycombing, form failures, dimensionalerrors, and finishing defects.

Honeycomb and rock pockets are areas ofconcrete where voids are left due to failure ofthe cement mortar to fill the spaces around andamong coarse aggregate particles. Thesedefects, if minor, can be repaired with cementmortar (section 25) if less than 24 hours haspassed since form removal. If repair is delayedlonger than 24 hours after form removal, or ifthe rock pocket is extensive, the area must beprepared and the defective concrete must beremoved and replaced with dry pack (section26), epoxy-bonded replacement concrete(section 31), or replacement concrete (section

29). Some minor defects resulting from formmovement or failure can be repaired withsurface grinding (section 24). More likely, theresulting defect is either simply accepted by theowner, or the contractor is required to removethe defective concrete and reconstruct thatportion of the structure.

There are many opportunities to createdimensional errors in concrete construction. Whenever possible, it usually is best to acceptthe resulting deficiency rather than attempt torepair it. If the nature of the deficiency is suchthat it cannot be accepted, then completeremoval and reconstruction is probably the best course of action. Occasionally,dimensional errors can be corrected byremoving the defective concrete and replacing itwith epoxy-bonded concrete or replacement


23

concrete.

Finishing defects usually involve overfinishingor the addition of water and/or cement to thesurface during the finishing procedures. In eachinstance, the resulting surface is porous andpermeable and has low durability. Poorlyfinished surfaces exhibit surface spalling earlyin their service life. Repair of surface spallinginvolves removal of the weakened concrete andreplacement with epoxy-bonded concrete(section 31). If the deterioration is detectedearly, the service life of the surface can beextended through the use of concrete sealingcompounds (sections 35 and 38).

14. Sulfate Deterioration.—Sodium,magnesium, and calcium sulfates are saltscommonly found in the alkali soils andgroundwaters of the Western United States. These sulfates react chemically with thehydrated lime and hydrated aluminate in cementpaste and form calcium sulfate and calciumsulfoaluminate. The volume of these reactionbyproducts is greater than the volume of thecement paste from which they are formed,causing disruption of the concrete fromexpansion. Type V portland cement, which hasa low calcium aluminate content, is highlyresistant to sulfate reaction and attack andshould be specified when it is recognized thatconcrete must be exposed to soil andgroundwater sulfates. See table 2 of theConcrete Manual (Bureau of Reclamation,1975) for guidance on materials and mixtureproportions for concretes exposed to sulfateenvironments.

Concrete that is undergoing active deteriorationand damage due to sulfate exposure cansometimes be helped by application of a thinpolymer concrete overlay (section 33) orconcrete sealing compounds (sections 35 and38). Alternate wetting and drying cyclesaccelerate sulfate deterioration, and someslowing of the rate of deterioration can beaccomplished by interrupting the cyclic wettingand drying. Procedures for eliminating orremoving waterborne sulfates are also helpful ifthis is the source of the sulfates. Otherwise, the

deteriorating concrete should be monitored forremoval and replacement with concreteconstructed of type V cement, whenappropriate.

15. Alkali-Aggregate Reaction.—Certaintypes of sand and aggregate, such as opal, chert,and flint, or volcanics with high silica content,are reactive with the calcium, sodium, andpotassium hydroxide alkalies in portland cementconcrete. These reactions, though observed andstudied for more than 50 years (Bureau ofReclamation, 1942), remain poorly defined andlittle understood. Some concrete containingalkali reactive aggregate shows immediateevidence of destructive expansion anddeterioration. Other concrete might remainundisturbed for many years. Petrographicexamination of reactive concrete shows that agel is formed around the reactive aggregate. This gel undergoes extensive expansion in thepresence of water or water vapor (a relativehumidity of 80 to 85 percent is all the waterrequired), creating tension cracks around theaggregate and expansion of the concrete (figure18). If unconfined, the expansion within theconcrete is first apparent by pattern cracking onthe surface. Usually, some type of whitishexudation will be evident in and around thecracked concrete. In extreme instances, thesecracks have opened 1.5 to 2 inches (figure 19). It is common for such expansion to causesignificant offsets in the concrete and binding orseizure of control gates on dams. In largeconcrete structures, alkali-aggregate reactionmay occur only in certain areas of the structure. Until it is recognized that multiple aggregatesources are commonly used to construct largeconcrete structures, this might be confusing. Only portions of the structure constructed withconcrete containing alkali reactive sand and/oraggregate will exhibit expansion due to alkali-aggregate reaction. This situation presentlyexists at Minidoka Dam (Stark and DePuy,1995), Stewart Mountain Dam, Coolidge Dam,Friant Dam, and Seminoe Dam.

In new construction, low alkali portlandcements and fly ash pozzolan can be used to


24

Figure 18.—Gel resulting from alkali-aggregate reaction causes expansion andtension cracks in a concrete core.

eliminate or greatly reduce the deterioration ofreactive aggregates. In existing concretestructures, deterioration due to reactiveaggregate is virtually impossible to mediate. There are no proven methods of eliminating thedeterioration of alkali-aggregate reaction,although the rate of expansion can sometimesbe reduced by taking steps to maintain theconcrete in as dry a condition as possible. It isusually futile to attempt repair of concreteactively undergoing alkali-aggregate reaction. The continuing expansion within the concretewill simply disrupt and destroy the repairmaterial. Structures undergoing activedeterioration should be monitored for rate ofexpansion and movement, and only the repairsnecessary to maintain safe operation of thefacility should be made. The binding gates ofseveral dams have been relieved and returned tooperation by using wire saws to make expansionrelief cuts in the concrete on either side of thebinding gates. The cuts were subsequentlysealed to water leakage using polyurethane resininjection techniques (section 34). Withcontinuing expansion of the concrete, suchrelief cuts may have to be repeated several

times. In many structures, the expansion andmovement associated with reactive aggregate slows down and ceases when all the alkalicomponents are consumed by the reactions. Once the expansion ceases, repairs can beperformed to rehabilitate and restore thestructure to full operation and serviceability. However, it should be anticipated that,ultimately, it may be necessary to replacestructures undergoing alkali-aggregatedeterioration. Such was the case with the 1975replacement of Reclamation's American FallsDam in Idaho. This dam was constructed in1927 and replaced after extensive studiesconducted by Reclamation’s Denver concretelaboratories revealed that it had been severelydamaged by alkali-aggregate reaction.

16. Deterioration Caused by Cyclic Freezingand Thawing.—Freeze-thaw deterioration is acommon cause of damage to concrete con-structed in the colder climates. For freeze-thawdamage to occur, the following conditions mustexist:

a. The concrete must undergo cyclicfreezing and thawing.


25

Figure 19.—Severe cracking caused by alkali-aggregate reaction.


26

b. The pores in the concrete, duringfreezing, must be nearly saturated with water (more than 90 percent ofsaturation).

Water experiences about 15 percent volumetricexpansion during freezing. If the pores andcapillaries in concrete are nearly saturatedduring freezing, the expansion exerts tensileforces that fracture the cement mortar matrix. This deterioration occurs from the outersurfaces inward in almost a layering manner. The rate of progression of freeze-thawdeterioration depends on the number of cyclesof freezing and thawing, the degree ofsaturation during freezing, the porosity of theconcrete, and the exposure conditions. The topsof walls exposed to snowmelt or water spray,horizontal slabs exposed to water, and verticalwalls at the water line are the locations mostcommonly damaged by freeze-thawdeterioration. If such concrete has a southernexposure, it will experience daily cycles offreezing during the night and thawing duringthe morning. Conversely, concrete with anorthern exposure may only experience onecycle of freezing and thawing each winter, a farless damaging condition. Figures 20 and 21show typical examples of freeze-thawdeterioration.

Another type of deterioration caused by cycles of freezing and thawing is known as D-cracking. In this instance, the expansionoccurs in low quality, absorptive, coarseaggregate instead of in the cement mortarmatrix. D-cracking is most commonly seen atthe exposed corners of walls or slabs formed byjoints. A series of roughly parallel cracksexuding calcite usually cuts across the cornersof such damage (figure 22).

In 1942, Reclamation began specifying the useof air entraining admixtures (AEA) in concreteto protect concrete from freezing and thawingdamage. Concrete structures built prior to thatdate did not contain AEA. Angostura Dam,started in 1946, was the first Reclamation Damconstructed with specifications requiring theuse of AEA (Price, 1981). This type of

admixture produces small air bubbles in theconcrete matrix that provide space for waterexpansion during freezing. If the proper AEA,at the correct concentration, is properly mixedinto high quality fresh concrete, there should bevery little damage resulting from cyclic freezingand thawing except in very severe climates. Accordingly, if freezing and thawing damage issuspected in modern concrete, investigationsshould be performed to determine why the AEAwas not effective. Except in cases of extremelycold and wet exposure, modern concreteexhibiting freeze-thaw damage has most likelysuffered low durability from some other cause(see section 23).

Damage caused by cyclic freezing and thawingof concrete occurs only when the concrete isnearly saturated. Successful mitigation offreeze-thaw deterioration, therefore, involvesreducing or eliminating the cycles of freezingand thawing or reducing absorption of waterinto the concrete. It usually is not practical toprotect or insulate concrete from cycles offreezing and thawing temperatures, but concretesealing compounds (sections 35 and 38) can beapplied to exposed concrete surfaces to preventor reduce water absorption. The sealingcompounds are not effective in protectinginundated concrete, but they can provideprotection to concrete exposed to rain,windblown spray, or snow melt water.

Repair of concrete damaged by freeze-thawdeterioration is most often accomplished withreplacement concrete (section 29) if the damageis 6 inches or deeper, or with epoxy- bondedreplacement concrete (section 31) or polymerconcrete (section 32) if the damage is between1.5 and 6 inches deep. The replacementconcretes must, of course, contain AEA. Attempted repair of spalls or shallow freeze-thaw deterioration less than 1.5 inches deep isdiscouraged. To date, no generic or proprietaryrepair material tested in the Denver laboratorieshas been found fully suitable for such shallowrepairs.

17. Abrasion-Erosion Damage.—Concretestructures that transport water containing silt,


27

Figure 20.—Freezing and thawing deterioration on small irrigation gate structure.

Figure 21.—Freezing and thawing deterioration on spillway concrete.


28

Figure 22.—D-cracking type of freezing and thawing deterioration.

sand, and rock or water at high velocities aresubject to abrasion damage. Dam stilling basinsexperience abrasion damage if the flows do notsweep debris from the basins. Some stillingbasins have faulty flow patterns that causedownstream sand and rock to be pulledupstream into the basins. This material isretained in the basins where it producessignificant damage during periods of high flow(figure 23). Abrasion damage results from thegrinding action of silt, sand, and rock. Concretesurfaces damaged in thisway usually have a polished appearance (figure24). The coarse aggregate often is exposed andsomewhat polished due to the action of the siltand sand on the cement mortar matrix. Figure25 shows an early stage of abrasion or, possibly,erosion damage to a stilling basin wall. Theextent of abrasion-erosion damage is a functionof so many variables—duration of exposure,shape of the concrete surfaces, flow velocityand pattern, flow direction, and aggregateloading—that it is difficult to develop generaltheories to predict concrete performance underthese conditions. Consequently, hydraulicmodel studies are often required to define the

flow conditions and patterns that exist indamaged basins and to evaluate requiredmodifications. If the conditions that causedabrasion-erosion damage are not addressed, thebest repair materials will suffer damage andshort service life.

It is generally understood that high qualityconcrete is far more resistant to abrasiondamage than low quality concrete, and anumber of studies (Smoak, 1991) clearlyindicate that the resistance of concrete increasesas the compressive strength of the concreteincreases.

Abrasion damage is best repaired with silicafume concrete (section 37) or polymer concrete(section 32). These materials have shown thehighest resistance to abrasion damage inlaboratory and field tests. If the damage doesnot extend behind reinforcing steel or at least 6 inches into the concrete, the silica fumeconcrete should be placed over a fresh epoxybond coat. Figure 26 shows the application ofsilica fume concrete to an area of abrasion,erosion, and freeze-thaw damage on the floor of


29

Figure 23.—Abrasion-erosion damage in a concrete stilling basin.

Figure 24.—Abrasion-erosion damage caused by sand or silt.


30

Figure 25.—Early stages of abrasion-erosion damage.

the Vallecito Dam spillway.

18. Cavitation Damage.—Cavitation damageoccurs when high velocity waterflows en-counter discontinuities on the flow surface. Discontinuities in the flow path cause the waterto lift off the flow surface, creating negativepressure zones and resulting bubbles of watervapor. These bubbles travel downstream andcollapse. If the bubbles collapse against aconcrete surface, a zone of very high pressureimpact occurs over an infinitely small area ofthe surface. Such high impacts can removeparticles of concrete, forming anotherdiscontinuity which then can create moreextensive cavitation damage. Figure 27 showsthe classic "Christmas tree" pattern of cavitationdamage that occurred in a large concrete-linedtunnel at Glen Canyon Dam during the floodreleases of 1982. In this instance, cavitationdamage extended entirely through the concretetunnel lining and some 40 feet into foundationrock (figure 28).

Cavitation damage is common on and aroundwater control gates and gate frames. Very high

velocity flows occur when control gates are firstbeing opened or at small gate openings. Suchflows cause cavitation damage just downstreamfrom the gates or gate frames.

The cavitation resistance of many differentrepair materials has been tested by thelaboratories of Reclamation, the U.S. ArmyCorps of Engineers, and others. To date, nomaterial, including stainless steel and cast iron,has been found capable of withstanding fullydeveloped instances of cavitation. Successfulrepairs must first include mediation of thecauses of cavitation.

A standard rule of thumb is that cavitationdamage will not occur at flow velocities lessthan about 40 feet per second at ambientpressures. As flow velocities approach thisthreshold, it becomes necessary to ensure thatthere are no offsets or discontinuities on thesurfaces in the flow path. Reclamation'sspecifications for finishing the surfaces ofconcrete structures that will experience highvelocity flows are very strict. Repairs to newlyconstructed concrete that fail to meet these


31

Figure 26.—Placing silica fume concrete to repair a spillway floor damaged bycyclic freezing and thawing and abrasion-erosion.


32

Figure 27.—Typical Christmas tree pattern of progressive cavitation damage.


33

Figure 28.—Extensive cavitation damage to Glen Canyon Dam.


34

requirements can sometimes be accomplishedby surface grinding (section 24). More likely,however, the concrete that does not meetsurface specifications must be removed andreplaced with replacement concrete (section 29)or epoxy-bonded replacement concrete (section31).

Cavitation damage at, or adjacent to, controlgates can usually be repaired with epoxy-bonded epoxy mortar (section 30), polymerconcrete (section 32), or epoxy-bondedreplacement concrete (section 31). Suchdamage is usually not very extensive in nature. That is, it is usually discovered before majorrepairs become necessary. After performingsuch repairs, it might be a good idea to apply a100-percent solids epoxy coating to theconcrete, beginning at the gate frame andextending downstream 5 to 10 feet. The glass-like surfaces of epoxy coatings may helpprevent cavitation damage to the concrete. Itshould be understood, however, that epoxycoatings will not resist fully developedinstances of cavitation damage.

Successful repair of cavitation damage tospillway, outlet works, or stilling basin concretealmost always requires making majormodifications to the damaged structure toprevent recurrence of damage. Performance ofhydraulic model studies should be considered toensure correctness of the design of such repairand facility modification. One modificationtechnique, the installation of air slots inspillways and tunnels, has been very successfulin eliminating or significantly reducingcavitation damage. Replacement concrete isusually used for construction of such featuresand the repair of the cavitation damage.

19. Corrosion of Reinforcing Steel.—Corrosion of reinforcing steel is usually asymptom of damage to concrete rather than acause of damage. That is, some other causeweakens the concrete and allows steel corrosionto occur. However, corroded reinforcing steel isso commonly found in damaged concrete thatthe purposes of this guide will best be served bydiscussing it as if it were a cause of damage.

The alkalinity of the portland cement used inconcrete normally creates a passive, basicenvironment (pH of about 12) around thereinforcing steel which protects it fromcorrosion. When that passivity is lost ordestroyed, or when the concrete is cracked ordelaminated sufficiently to allow free entranceof water, corrosion can occur. The iron oxidesformed during steel corrosion require morespace in the concrete than the originalreinforcing steel. This creates tensile stresseswithin the concrete and results in additionalcracking and/or delamination which acceleratethe corrosion process.

Some of the more common causes of corrosionof reinforcing steel are cracking associated withfreeze-thaw deterioration, sulfate exposure, andalkali-aggregate reaction, acid exposure, loss ofalkalinity due to carbonation, lack of sufficientdepth of concrete cover, and exposure tochlorides.

Exposure to chlorides greatly accelerates therates of corrosion and can occur in severalmanners. The application of deicing salts(sodium chloride) to concrete to acceleratethawing of snow and ice is a common source ofchlorides. Chlorides can also occur in the sand,aggregate, and mixing water used to prepareconcrete mixtures. Some irrigation structureslocated in the Western States transport watersthat have high chloride contents (figure 29). Concrete structures located in marineenvironments experience chloride exposurefrom the sea water or from windblown spray. Finally, it was once a somewhat commonpractice to use concrete admixtures containingchlorides to accelerate the hydration of concreteplaced during winter conditions.

The occurrence of corroding reinforcing steelcan usually, but not always, be detected by thepresence of rust stains on the exterior surfacesand by the hollow or drummy sounds that resultfrom tapping the affected concrete with ahammer. It can also be detected by measuringthe half cell potentials of the affected concreteusing special electronic devices manufacturedspecifically for this purpose. When the


35

Figure 29.—Concrete damage caused by chloride-induced corrosion of reinforcing steel.The waters contained within this flume had high chloride content.

presence of corroding steel has been confirmed,it is important to define what actually causedthe corrosion because the cause(s) of corrosionwill usually determine which repair procedureshould be used. Further discussion of suchrepair procedures can be found elsewhere inthis guide. Once the cause of damage has beendefined and mitigated, if necessary, properpreparation of the corroded steel exposedduring removal of the deteriorated concretebecomes important. Steel that has been reducedto less than half its original cross section by thecorrosion process should be removed andreplaced. The remaining steel must then becleaned to remove all loose rust, scale, andcorrosion byproducts that would interfere withthe bond to the repair material. Corrodedreinforcing steel may extend from areas ofobviously deteriorated concrete well into areasof apparently sound concrete. Care must betaken to remove sufficient concrete to includeall the corroded steel.

20. Acid Exposure.—The more commonsources of acidic exposure involving concretestructures occur in the vicinity of under-ground

mines. Drainage waters exiting from suchmines can contain acids of sometimesunexpectedly low pH value. A pH value of 7 isdefined as neutral. Values higher than 7 aredefined as basic, while pH values lower than 7 are acidic. A 15- to 20-percent solution ofsulfuric acid will have a pH value of about 1. Such a solution will damage concrete veryrapidly. Acidic waters having pH values of 5 to 6 will also damage concrete, but only afterlong exposure.

Concrete damaged by acids is very easy todetect. The acid reacts with the portlandcement mortar matrix of concrete and convertsthe cement into calcium salts that slough off orare washed away by flowing waters. The coarseaggregate is usually undamaged but leftexposed. The appearance of acid-damagedconcrete is somewhat like that of abrasiondamage, but the exposure of the coarseaggregate is more pronounced and does notappear polished. Figures 30 and 31 show thetypical appearance of concrete that has beendamaged by acid exposure. Acid damagebegins, and is most pronounced, on the exposed


36

Figure 30.—Concrete deterioration caused by acidic water.

Figure 31.—The depth of acidic water on this concrete wall is very apparent.


37

surface of concrete but always extends, to adiminishing extent, into the core of thestructure. The acid is most concentrated at thesurface. As it penetrates into the concrete, it isneutralized by reaction with the portlandcement. The cement at depth inside thestructure, however, is weakened by the reaction. Preparation of acid-damaged concrete,therefore, always involves removal of moreconcrete than would otherwise be expected. Failure to remove all the concrete affected andweakened by the acid will result in bond failureof the repair material. Acid washes were oncepermitted as a method of cleaning concretesurfaces in preparation for repairs. It has beenlearned, however, that bond failures wouldoccur unless extensive efforts were expended toremove all traces of acid from the concrete. Reclamation specifications no longer permit theuse of acid washes to prepare concrete forrepair or to clean cracks subject to resininjection repairs.

As with all causes of damage to concrete, it isgenerally necessary to remove the source ofdamage prior to repair. The most commontechnique used with acid damage is to dilute theacid with water. Low pH acid solutions can beconverted to higher pH solutions having far lesspotential for damage in this manner.Alternately, if the pH of the acid solution isrelatively high, coatings such as the thinpolymer concrete coating system, section 33,can be applied over repair materials to preventthe acid from redamaging the surfaces. Laboratory tests have revealed very feweconomical coatings capable of protectingrepair materials from low pH solutions.

Repairs to acid-damaged concrete can be madeusing epoxy-bonded replacement concrete(section 31), replacement concrete (section 29),polymer concrete (section 32), and, in someinstances, epoxy-bonded epoxy mortar (section30). Polymer concrete and epoxy mortar, whichdo not contain portland cement, offer the mostresistance to acid exposure conditions.

21. Cracking.—Cracking, like corrosion ofreinforcing steel, is not commonly a cause of

damage to concrete. Instead, cracking is asymptom of damage created by some othercause.

All portland cement concrete undergoes somedegree of shrinkage during hydration. Thisshrinkage produces multidirectional dryingshrinkage and curing shrinkage cracking havinga somewhat circular pattern (figure 32). Suchcracks seldom extend very deeply into theconcrete and can generally be ignored.

Plastic shrinkage cracking occurs when thefresh concrete is exposed to high rates ofevaporative water loss which causes shrinkagewhile the concrete is still plastic (figure 33). Plastic shrinkage cracks are usually somewhatdeeper than drying or curing shrinkage cracksand may exhibit a parallel orientation that isvisually unattractive.

Thermal cracking is caused by the normalexpansion and contraction of concrete duringchanges of ambient temperature. Concrete hasa linear coefficient of thermal expansion ofabout 5.5 millionths inch per inch per degreeFahrenheit (°F). This can cause concrete toundergo length changes of about 0.5 inch per100 linear feet for an 80 °F temperature change. If sufficient joints are not provided by thedesign of the structure to accommodate thislength change, the concrete will simply crackand provide the joints where needed. This typeof cracking will normally extend entirelythrough the member and create a source ofleakage in water retaining structures. Thermalcracking can also be caused by using portlandcements developing high heats of hydrationduring curing. Such concrete developsexothermic heat and hardens while at elevatedtemperatures. Subsequent contraction uponcooling develops internal tensile stresses andresulting cracks at or across points of restraint.

Inadequate foundation support is anothercommon cause of cracking in concretestructures. The tensile strength of concrete isusually only about 200 to 300 psi. Foundationsettlement can easily create displacementconditions where the tensile strength of concrete


38

Figure 32.—Typical appearance of drying shrinkage cracking.


39

Figure 33.—Plastic shrinkage cracking caused by high evaporative water loss whilethe concrete was still in a plastic state.

is exceeded with resulting cracking.

Cracking is also caused by alkali-aggregatereaction, sulfate exposure, and exposure tocyclic freeze-thaw conditions, as has beendiscussed in previous sections, and by structuraloverloads as discussed in the following section.

Successful repair of cracking is often verydifficult to attain. It is better to leave mosttypes of concrete cracking unrepaired than toattempt inadequate or improper repairs (figure34 and 35). The selection of methods forrepairing cracked concrete depends on thecause of the cracking. First, it is necessary todetermine if the cracks are "live" or "dead." Ifthe cracks are cyclicly opening and closing, orprogressively widening, structural repairbecomes very complicated and is often futile. Such cracking will simply reestablish in therepair material or adjacent concrete. For thisreason, it is normal procedure to install crackgages across the cracks to monitor theirmovement prior to attempting repair (figure 36). The gages should be monitored for extendedperiods to determine if the cracks are simply

opening and closing as a result of daily orseasonal temperature changes or if there is acontinued or progressive widening of the cracksresulting from foundation or

load conditions. Repairs should be attemptedonly after the cause and behavior of thecracking is understood.

If it is determined that the cracks are "dead" orstatic, epoxy resin injection (section 34) can beused to structurally rebond the concrete. If theobjective of the repair is to seal water leakagerather than to accomplish structural rebonding,the cracks should be injected with polyurethaneresin. Epoxy resin injection can sometimes beused to seal low volume water leakage andstructurally rebond cracked concrete members. Epoxy resins cure to form hard, brittle materialsthat will not withstand movement of the injectedcracks. Poly-urethane resins cure to a flexible,low tensile strength, closed cell foam that iseffective in sealing water leakage but cannotnormally be used for structural rebonding. (Some two component polyurethane resinsystems cure to form flexible solids that may be


40

Figure 34.—Inadequate crack repair techniques often result in poor appearance upon completion.

Figure 35.—Improper crack repair techniques often result in short service life.


41

Figure 36.—Crack gage installed across a crack will allow determination of progressivewidening or movement of the crack. It may be necessary to monitor such

gages for periods up to a year to predict future crack behavior.

useful for structural rebonding.) These flexiblefoams can experience 300- to 400-percentelongation due to crack movement. It is notuncommon to find that damaged concretecontains cracking not related to the cause of theprimary damage (see section 23). If the depthof removal of the damaged or deterioratedconcrete does not extend below the depth andextent of the existing cracks, it should beexpected that the cracking will ultimately reflectthrough the new repair materials. Suchreflective cracking is common in bondedoverlay repairs to bridge decks, spillways, andcanal linings (figure 37). If reflective crackingis intolerable, the repairs must be designed asseparate structural members not bonded to theold existing concrete.

22. Structural Overloads.—Concrete damagecaused by structural overloading is usually veryobvious and easy to detect. Frequently, theevent causing overloading has been noted and isa matter of record. The stresses created byoverloads result in distinctive patterns of

cracking that indicate the source and cause ofexcessive loading and the point(s) of loadapplication. Normally, structural overloads areone time events and, once defined, the resultingdamage can be repaired with the expectationthat the cause of the damage will not reoccur tocreate damage in the repaired concrete.

It should be expected that the assistance of aknowledgeable structural engineer will berequired to perform the structural analysisneeded to fully define and evaluate the causeand resulting damage of most structuraloverloads and to assist in determining the extentof repair required. This analysis should includedetermination of the loads the structure wasdesigned to carry and the extent the overloadexceeded design capacity. A thoroughinspection of the damaged concrete must beperformed to determine the entire effect of theoverload on the structure. Displacements mustbe discovered and the secondary damage, if any,located. Care should be taken to ensure thatsome other cause of damage did not first


42

Figure 37.—A large reflective crack has formed in a concrete overlay which alsoexhibits circular drying shrinkage cracking.


43

weaken the concrete and make it incapable ofcarrying the design loads. The repair of damagecaused by overloading can, most likely, best beperformed with conventional replacementconcrete (section 29). The need for repairand/or replacement of damaged reinforcingsteel should be anticipated and included in therepair procedures.

23. Multiple Causes of Damage.—Multiplecauses of the damage should be suspectedwhenever damage or deterioration is discoveredin modern concrete. Modern concrete (concreteconstructed since about 1950) has the benefit ofthe use of various admixtures and advancedconcrete materials technology. Such concreteshould not be damaged by many of the causeslisted in this chapter. If deterioration or damagehas occurred, it is likely that a combination ofcauses are in effect. Failure to recognize andmitigate all the causes of damage will mostlikely result in poor repair serviceability. Figure 38 shows the results of multiple causedamage. This concrete is suffering from alkali-aggregate reaction cracking that has alsoaccelerated freeze-thaw deterioration of thesurface. It is also being damaged by faultydesign or construction techniques that locatedthe electrical conduits too close to the exteriorsurface of the concrete.

The proper use of air entraining admixtures inmodern concrete has greatly increased theresistance of the concrete to freeze-thawdeterioration. Except in unusually severeexposures, freeze-thaw deterioration should notoccur. This notwithstanding, freeze-thawdeterioration is often still blamed as the causeof damage to modern concrete. Before blamingfreezing and thawing conditions, it is better tofirst determine why the air entraining admixturedid not provide effective protection. Mixrecords and aggregate quality

test results may indicate that the concrete waspoorly proportioned or that the availableaggregate was of low quality. Constructioninspection records may indicate that placing andfinishing techniques were inadequate. Petrographic examination of the affectedconcrete may reveal that alkali-aggregatereaction, sulfate exposure, or induced chlorideshave weakened the concrete and allowed freeze-thaw damage to occur. All such findings mightindicate that the problem is far more extensivethan at first thought and requires more extensivepreventative or corrective action than the simplereplacement of the presently deterioratedconcrete.

The use of excessive mix water, the impropertype of portland cement, poor constructionpractices, improper mixture proportioning, dirtyor low quality aggregate, and inadequate curingall contribute to low durability in concrete. Such concrete may have low resistance tonormal weathering or to other hazards.

Selection of the proper methods and materialsfor repair of concrete damaged by multiplecauses depends on determining which is theweakening cause and which is the acceleratedcause. Once the weakening cause is fullyunderstood, it is commonly necessary to takepreventative measures to protect the re-mainingoriginal concrete from additional damage. Theapplication of concrete sealing compounds(sections 35 and 38) or the thin polymerconcrete overlay (section 32) may prove usefulin this respect. If no such preventativemeasures are judged useable, repair of thedamaged concrete can be made as discussed inprevious sections, but short repair service lifeand the occurrence of future damage should beanticipated.


44

Figure 38.—Multiple causes of damage are apparent in this photograph. Poordesign or construction practices placed the electrical conduit too near thesurface. A combination of freezing and thawing deterioration and alkali-

aggregate reaction is responsible for the cracking and surfacespalling on the parapet wall.

45

Chapter IV

Standard Methods of Concrete Repair

Proven methods of repairing concrete aredescribed in this chapter. Sections 24 through38 contain detailed discussions of each of theproven repair methods. Constructionspecifications for these methods/materials ofrepair are contained in the latest revision ofReclamation's Standard Specifications for theRepair of Concrete, M-47, Appendix A. It isessential that the provisions of thesespecifications be closely followed during repairof Reclamation concrete. It should berecognized, however, that these "standard"methods and specifications cannot apply tounusual or nonstandard concrete repairsituations. Assistance with unusual or specialrepair problems can readily be obtained bycontacting personnel of the MaterialsEngineering and Research Laboratories, Code D-8180.

24. Surface Grinding.—Surface grinding canbe used to repair some bulges, offsets, and otherirregularities that exceed the desired surfacetolerances. Excessive surface grinding,however, may result in weakening of theconcrete surface, exposure of easily removedaggregate particles, or unsightly appearance. For these reasons, surface grinding should beperformed subject to the following limitations:

a. Grinding of surfaces subject to cavitationerosion (hydraulic surfaces subject to flowvelocities exceeding 40 feet per second)should be limited in depth so that noaggregate particles more than 1/16 inch incross section are exposed at the finishedsurface.

b. Grinding of surfaces exposed to publicview should be limited in depth so that noaggregate particles more than 1/4 inch incross section are exposed at the finished

surface.c. In no event should surface grinding result

in exposure of aggregate of more than one-half the diameter of the maximum sizeaggregate.

Where surface grinding has caused or will causeexposure of aggregate particles greater than thelimits of subparagraph 24.a. or b., the concretemust then be repaired by excavating andreplacing the concrete in accordance withsections 29, 30, 31, or 32.

25. Portland Cement Mortar.—Portlandcement mortar may be used for repairing defectson surfaces not prominently exposed, where thedefects are too wide for dry pack filling orwhere the defects are too shallow for concretefilling and no deeper than the far side of thereinforcement that is nearest the surface. Repairs may be made either by use of shotcreteor by hand application methods. Replacementmortar can be used to make shallow, small sizerepairs to new or green concrete, provided thatthe repairs are performed within 24 hours ofremoving the concrete forms.

The use of replacement mortar to repair old ordeteriorated concrete has been permitted onReclamation projects in the past. It is nowrecognized, however, that accomplishingsuccessful mortar repairs to old concretewithout the use of a bonding resin is unlikely orextremely difficult. Evaporative loss of waterfrom the surface of the repair mortar, combinedwith capillary water loss to the old concrete,results in unhydrated or poorly hydrated cementin the mortar. Additionally, repair mortar bondstrength development proceeds at a slower ratethan compressive strength development. Thiscauses workers to mistakenly abandon curingprocedures prematurely, when the mortar


46

"seems strong." Once the mortar dries, bondstrength development stops, and bond failure ofthe mortar patch results.

For these reasons, using cement mortar withouta resin bond coat to repair old concrete isdiscouraged and is not allowed underReclamation's Standard Specifications for theRepair of Concrete, M-47.

A portland cement mortar patch is usuallydarker than the surrounding concrete unlessprecautions are taken to match colors (figure39). A leaner mix will usually produce a lightercolor patch. Also, white cement can be used toproduce a patch that will blend with thesurrounding concrete. The quantity of whitecement to use must be determined by trial.

(a) Preparation.—Concrete to be repaired withreplacement mortar should be prepared inaccordance with the provisions of section 8. After preparation, the areas should be cleaned,roughened, if necessary (preferably by wetsandblasting), and surface dried to a saturatedsurface condition. The mortar should beapplied immediately thereafter.

(b) Materials.—Replacement mortar containswater, portland cement, and sand. The cementshould be same type as used in the concretebeing repaired. The water and sand should besuitable for use in concrete, and the sand shouldpass a No. 16 sieve. The cement to sand ratioshould be between 1:2 to 1:4, depending onapplication technique. Only enough watershould be added to the cement-sand mixture topermit placing.

(c) Application.—Best results with replacementmortar are obtained when the material ispneumatically applied using a small gun. Equipment commonly used for shotcreting istoo large to be satisfactory for the ordinarilysmall size mortar repairs of new concrete. Withshotcreting equipment, neat work is difficult inthe usual small areas, and cleanup costs arehigh because cleanup is seldom done promptly. However, small size equipment such as shownin figure 40 has been satisfactory for small scale

repair work when the mortar was premixed,including water, to a consistency of dry-packmaterial. No initial application of cement,cement grout, or wet mortar should be made. Ifrepairs are more than 1 inch deep, the mortarshould be applied in layers not more than 3/4 ofan inch thick to avoid sagging and loss of bond.After completion of each layer, there should bea lapse of 30 minutes or more before the nextlayer is placed. Scratching or otherwisepreparing the surface of a layer prior to additionof the next layer is unnecessary, but the mortarmust not be allowed to dry.

In completing the repair, the hole should befilled slightly more than level full. After thematerial has partially hardened but can still betrimmed off with the edge of a steel trowel,excess material should be shaved off, workingfrom the center toward the edges. Extreme caremust be used to avoid impairment of bond. Neither the trowel nor water should be used infinishing. A satisfactory finish may be obtainedby lightly rubbing the surface with a soft rag.

For minor restorations, satisfactory mortarreplacement may be performed by hand. Thesuccess of this method depends on completeremoval of all defective and affected concrete,good bonding of the mortar to the concrete,elimination of shrinkage of the patch afterplacement, and thorough curing.

Replacement mortar repairs can be made usingan epoxy bonding agent as described in section26. This technique, while not required byReclamation's M-47 specifications, is highlyrecommended.

(d) Curing.—Failure to cure properly is themost common cause of failure of replacementmortar. It is essential that mortar repairsreceive a thorough water cure startingimmediately after initial set and continuing for14 days. In no event should the mortar beallowed to become dry during the 14-day periodfollowing placement. Following the 14-daywater cure and while the mortar is stillsaturated, the surface of the mortar should


47

Figure 39.—A portland cement mortar patch seldom matches the color of the originalconcrete unless special efforts are taken to blend white cement with normal portlandcement.

Figure 40.—A small size pneumatic gun can be used to apply portland cementmortar. Regular shotcreting equipment would be too large for this application.


48

be coated with two coats of a wax-base orwater-emulsified resin base curing compoundmeeting Reclamation specifications. If thiscuring procedure cannot be followed or ifconditions at the job are such that this curingprocedure will not be followed, money wouldbe saved by using another repair material.

26. Dry Pack and Epoxy-Bonded DryPack.—Dry pack is a combination of portlandcement and sand passing a No. 16 sieve mixedwith just enough water to hydrate the cement. Dry pack should be used for filling holes havinga depth equal to, or greater than, the leastsurface dimension of the repair area; for conebolt, she bolt, core holes, and grout-insert holes;for holes left by the removal of form ties; andfor narrow slots cut for repair of cracks. Drypack should not be used for relatively shallowdepressions where lateral restraint cannot beobtained, for filling behind reinforcement, or forfilling holes that extend completely through aconcrete section. For the dry pack method of concrete repair,holes should be sharp and square at the surfaceedges, but corners within the holes should berounded, especially when water tightness isrequired. The interior surfaces of holes left bycone bolts and she bolts should be roughened todevelop an effective bond; this can be done witha rough stub of 7/8-inch steel-wire rope, anotched tapered reamer, or a star drill. Otherholes should be undercut slightly in severalplaces around the perimeter, as shown in figure41. Holes for dry pack should have a minimumdepth of 1 inch.

(a) Preparation.—Application of dry packmortar should be preceded by a carefulinspection to see that the hole is thoroughlycleaned and free from mechanically held loosepieces of aggregate. One of the three followingmethods should be used to ensure good bond ofthe dry pack repair.

The first method is the application of a stiffmortar or grout bond coat immediately beforeapplying the dry pack mortar. The mix for thebonding grout is 1:1 cement and fine sand

mixed with water to a fluid paste consistency. All surfaces of the hole are thoroughly brushedwith the grout, and dry packing is done quicklybefore the bonding grout can dry. Under nocircumstances should the bonding coat be sowet or applied so heavily that the dry packmaterial becomes more than slightly rubbery. When a grout bond coat is used, the hole to berepaired can be dry. Presoaking the holeovernight with wet rags or burlap prior to drypacking may sometimes give better results byreducing the loss of hydration water, but theremust be no free surface water in the hole whenthe bonding grout is applied.

The second method of ensuring good bondstarts with presoaking the hole overnight withwet rags or burlap. The hole is left slightly wetwith a small amount of free water on the insidesurfaces. The surfaces are then dusted lightlyand slowly with cement using a small dry brushuntil all surfaces have been covered and the freewater absorbed. Any dry cement in the holeshould be removed using a jet of air beforepacking begins. The hole should not be paintedwith neat cement grout because it could makethe dry pack material too wet and because highshrinkage would prevent development of thebond that is essential to a good repair.

A third method of ensuring good bond is the useof an epoxy bonding resin. The epoxy bondingresin should meet the requirements of ASTM C-881 for a type II, grade 2, class B or C resin,depending on the job site ambient temperatures. Epoxies bond best to dry concrete. It may benecessary to dry the hole immediately prior todry packing using hot air, a propane torch, orother appropriate method. The concretetemperature, however, should not be highenough to cause instant setting of the epoxy orto burn the epoxy when it is applied. Afterbeing mixed, the epoxy is thoroughly brushed tocover all surfaces, but any excess epoxy isremoved. Dry pack mortar is then appliedimmediately, before the epoxy starts to harden. The epoxy must be either fluid or tacky whendry packing takes place. If it appears that theepoxy may become hard before dry packing is


49

Figure 41.—Saw-tooth bit used to cut slot for dry packing.

complete, fresh fluid epoxy can be brushed overepoxy that has become tacky. If the epoxybecomes hard, it must be removed before a newcoat is applied. The epoxy ensures a good bondbetween the dry pack repair and the oldconcrete. It also reduces the loss of hydrationwater from the repair to the surroundingconcrete, thus assisting in good curing;however, the epoxy-bonded dry pack stillrequires curing as discussed below. Whereappearance is not important, epoxy hassometimes been used on the surface in place ofa curing compound. This procedure is notrecommended and is not allowed onReclamation jobs.

(b) Materials.—Dry pack mortar is usually amixture (by dry volume or weight) of 1 partcement to 2-1/2 parts sand that will pass a No. 16 screen. While the mixture is rich incement, the low water content preventsexcessive shrinkage and gives high strengths. Adry pack repair is usually darker than thesurrounding concrete unless special precautionsare taken to match the colors. Where uniformcolor is important, white cement may be used in

sufficient amount (as determined by trial) toproduce uniform appearance. For packing conebolt holes, a leaner mix of 1:3 or 1:3-1/2 will besufficiently strong and will blend better with thecolor of the wall. Sufficient water should beused to produce a mortar that will just sticktogether while being molded into a ball with thehands and will not exude water but will leavethe hands damp. The proper amount of waterwill produce a mix at the point of becomingrubbery when solidly packed. Any less waterwill not make a sound, solid pack; any more willresult in excessive shrinkage and a loose repair.

(c) Application.—Dry pack mortar should beplaced and packed in layers having a compactedthickness of about three-eighths of an inch. Thicker layers will not be well compacted at thebottom. The surface of each layer should bescratched to facilitate bonding with the nextlayer. One layer may be placed immediatelyafter another unless an appreciable rubberyquality develops; if this occurs, work on therepair should be delayed 30 to 40 minutes. Under no circumstances should alternate layersof wet and dry materials be used.


50

Each layer should be solidly compacted over theentire surface by striking a hardwood dowel orstick with a hammer. These sticks are usually 8to 12 inches long and not over 1 inch indiameter and are used on fresh mortar like acaulking tool. Hardwood sticks are used inpreference to metal bars because the latter tendto polish the surface of each layer and, thus,make bonding less certain and filling lessuniform. Much of the tamping should bedirected at a slight angle and toward the sides ofthe hole to ensure maximum compaction inthese areas. The holes should not be overfilled;finishing may usually be completed at once bylaying the flat side of a hardwood piece againstthe fill and striking it several good blows with ahammer. If necessary later, a few light strokeswith a rag may improve appearance. Steelfinishing tools should not be used, and watermust not be used to facilitate finishing.

(d) Curing and Protection.—Procedures for curing and protection of dry pack areessentially the same as those for concrete andare described in section 25. Additionally, thedry pack repair area should be protected and notexposed to freezing temperatures for at least 3days after application of the curing compound.

27. Preplaced Aggregate Concrete.—Preplaced aggregate concrete is an excellentrepair material that has not been used much inrecent years. Preplaced aggregate concrete ismade by injecting portland cement grout, withor without sand, into the voids of a formed,compacted mass of clean, graded, coarseaggregate. The preplaced aggregated is washedand screened to remove fines before placinginto the forms. As the grout is injected orpumped into the forms, it displaces anyincluded air or water and fills the voids aroundthe aggregate, thus creating a dense concretehaving a high aggregate content.

Because the coarse aggregate has point contactprior to grout injection, preplaced aggregateconcrete undergoes very little settlement,curing, or drying shrinkage during hydration. Drying shrinkage of preplaced aggregateconcrete containing 1-1/2 inch maximum size

aggregate is about 200 to 400 millionths, whileconventional concrete drying shrinkagecontaining the same size maximum aggregate isabout 400 to 600 millionths.

Another advantage of preplaced aggregateconcrete is the ease with which it can be placedin certain situations where placement ofconventional concrete would be extremelydifficult or impossible. Preplaced aggregateconcrete is especially useful in underwaterrepair construction. It has been used in avariety of large concrete and masonry repairs,including bridge piers and the resurfacing ofdams. It has been used to construct atomicreactor shielding and plugs for outlet works andtunnels in mine workings, and it has been usedto embed penstocks and turbine scrollcases(American Concrete Institute, 1992). Figure 42shows the upstream face of Barker Dam nearBoulder, Colorado, which was resurfaced withprepacked aggregate concrete.

Although preplaced aggregated is adaptable tomany special repair applications, it is essentialthat the work be undertaken by well qualifiedpersonnel who are willing to follow exactly theconstruction procedures required for this repairmaterial. Form work for preplaced aggregateconcrete requires special attention to preventgrout loss. The construction of forms should bewith workmanship better than that normallyencountered with conventional concrete. Leaking forms can cause significant problemsand should, by careful construction, be avoidedwhenever possible. The injected grout is moreflowable than plastic concrete and takes slightlylonger to set. Forms, therefore, must beconstructed to take more lateral pressure thanwould be necessary with conventional concrete. Form bolts should fit tightly through thesheathing, and all possible points of groutleakage should be caulked.

(a) Preparation The preparation of concrete tobe repaired by preplaced aggregate concrete isidentical to the preparation required forreplacement concrete (section 29) if thedevelopment of bond is required.


51

Figure 42.—The downstream face of Barker Dam, near Boulder, Colorado,was resurfaced with prepacked aggregate.

(b) Materials .—Grout for preplaced aggregateconcrete may be mixed with sand either of thegradation specified for conventional concrete orwith fine sand, pozzolanic or fly ash fillers,water reducing admixtures, and pumpingadmixtures as dictated by the minimum size ofthe coarse aggregate. With 1-1/2-inch minimumsize coarse aggregate, the sand gradation is thatspecified for conventional concrete. Theportland cement, water, and sand are mixedusing high speed centrifugal grout mixers thatproduce well mixed grouts of a creamyconsistency. For use with 1/2-inch minimumsize coarse aggregate, a grout mixture isprepared containing fine sand passing a No. 8screen and with at least 95 percent passing a No.16 screen. Best pumping characteristics will beobtained with fineness modulus between 1.2 and2 and with the rounded shape of natural sands asopposed to crushed sands.

Addition of fly ash and water reducingadmixture improves the flowability of the grout

and the ultimate strength. Proprietary pumpingadmixtures are commonly used to increase thepenetration and pumpability of the final grout. The consistency of grout for preplacedaggregated should be uniform from batch tobatch and should be such that it can be readilypumped into the voids at relatively low pressure. Consistency is affected by water content, sandgrading, filler type and content, cement type, andadmixture type. For each mix, there are optimumproportions that produce best grout pumpabilityor consistency, and tests are necessary for eachjob to determine these optimum proportions.

The maximum size coarse aggregate used withboth types of grout is the largest available,provided that the aggregate can be easily handledand placed. Coarse aggregate should meet all therequirements of coarse aggregate forconventional concrete. It is essential that thecoarse aggregated be clean. The aggregateshould be well graded from minimum size (1/2-inch minimum or 1-1/2-inch minimum) up to the


52

maximum size, and when compacted into theforms, should have a void content of 35 to 40percent. If grout containing sand of concretegrading is used, the minimum coarse aggregatesize should be 1-1/2 inches.

(c) Application.—The grout piping system usedwith preplaced aggregate concrete must bedesigned to serve at least 3 purposes—to deliverand inject grout, to provide means fordetermining grout level in the forms, and toserve as vents in enclosed forms for escape orair and water. Proper design and location of thegrout piping system is essential for successfulplacement. The grout delivery pipeline should be arecirculating system. That is, the grout deliverypipeline should extend from the grout agitator orholding tank to the grout pump, then to theinjection manifold, and return to the groutagitator tank. With this type of pipeline, thegrout can be kept moving and circulating in thedelivery pipeline even when no grout is beinginjected into the aggregate. Such a systemprevents stoppages and clogging of the deliveryline. Noncirculating or deadheaded groutdelivery lines are not allowed on Reclamationprojects. The delivery line should be kept asshort as practicable, and the pipe size should besuch that normal grout flow velocities rangebetween 2 and 4 feet per second. For mostapplications, a 1-inch ID grout line will suffice. All valves used in the grout piping systemshould be quick opening ball valves which canbe readily cleaned.

The simplest piping system is a singlerecirculating delivery line attached via amanifold and valves to a single injection line. The injection line should extend to the lowestpoint in the form. Multiple injection lines areused for larger projects. Spacing of theinjection lines is variable, depending on theform configuration, aggregate gradation, andother factors, but spacings of 4 to 6 feet arecommon. In preparing the layout of the groutdelivery system, it is normally assumed that theslope of the grout face will be 4:1 for work inthe dry and 6:1 for underwater work. Much

flatter slopes are common with actual groutsurfaces.

Sounding wells constructed from 2-inch-diameter slotted pipe are installed to allowdetermination of the level of grout duringinjection. Similarly, clear plastic windows canbe installed in the forms to allow visualdetermination of grout levels. The number andlocation of sounding wells are determined by thesize and configuration of the aggregate mass. The ratio of sounding wells to injection pipesshould be from 1:4 to about 1:8.

Grout injection should begin at the lowest pointof the form and continue uniformly until theentire form is filled. After sufficient grout hasbeen pumped to raise the level of grout in theform about 18 inches above the bottom outlet ofthe injection line, the injection line can beprogressively raised, maintaining about 12 inchesof embedment below the level of the grout at alltimes. A great deal of thought and planning isrequired if multiple injection lines are used. Theobjective is to entirely fill the form withouttrapping air or water. Vents must be locatedwhere needed and the injection sequencedesigned to promote complete filling. It is notpossible to use internal vibrators to consolidatepreplaced aggregate concrete. External vibrators,however, can be attached to the forms and usedadvantageously. External vibration willeliminate the splotchy appearance that can occurwhere coarse aggregate particles contact theforms. Underwater applications of preplacedaggregate concrete require additionalconsiderations. During injection, grout pumpingmust continue until an undiluted flow of groutemerges from the top of the form. Formwork isusually closed at the top to prevent washout ordilution of the grout after placement if flowingwater is encountered. Anti-washout admixturesmight prove useful for underwater applications ofpreplaced aggregate concrete. Care must betaken, however, when using several differenttypes of admixtures (e.g., anti-washout, pumpingaids, or high range water reducers) thatundesirable combinations are avoided. It isknown for example, that some anti-washoutadmixtures can significantly reduce the


53

pumpability benefits of some high range waterreducers. Such problems should be detectedduring the mixture proportioning testspreviously recommended in paragraph (b).

The minimum volume of the grout mixer tankand the grout agitator tank should be 17 cubicfeet. The grout should be mixed using a highspeed centrifugal mixer operating at a mini-mum of 1,500 rotations per minute. The groutpump should be of the helical screw, rotor-type(commonly known as a "Moyno" grout pump),capable of pumping at least 20 gallons of groutper minute at the specified injection pressure.

Quality control of preplaced aggregate concretelies with proper compaction of the aggregateinto the forms and maintenance of proper groutconsistency throughout the job. Compactionrequirements must be satisfied by visualinspection during placement and before grout isintroduced into the forms. Grout consistencycan be determined by using a Baroid Model 140Mud Balance to measure grout density. Somepractitioners promote using a flow cone to timethe rate of flow of a known volume of groutthrough the cone as a measure of consistency. Recent laboratory tests (Smoak, 1993), however,have proven that the flow cone is useless formeasuring the consistency of grout containinghigh range water reducing admixture.

(d) Curing.—The curing requirements forpreplaced aggregate concrete are the same as forreplacement concrete (section 29). Preplacedaggregate concrete placed during underwaterapplications will normally receive excellentcuring without further effort.

28. Shotcrete.—Shotcrete is defined as "mortaror concrete pneumatically projected at highspeed onto a surface" (American ConcreteInstitute, 1990). There are two basic types ofshotcrete—dry mix and wet mix. In dry mixshotcrete, the dry cement, sand, and coarseaggregate, if used, are premixed with onlysufficient water to reduce dusting. This mixtureis then forced through the delivery line to thenozzle by compressed air (figure 43). At thenozzle, sufficient water is added to the moving

stream to meet the requirements of cementhydration. Figure 44 shows the nozzle and waterring of a dry mix shotcrete nozzle. For wet mixshotcrete, the cement, sand, and coarse aggregateare first conventionally mixed with water (figure45), and the resulting concrete is then pumped tothe nozzle where compressed air propels the wetmixture onto the desired surface (figure 46). Thetwo types of shotcrete produce mixes withdifferent water contents and different applicationcharacteristics as a result of the distinctlydifferent mixing processes. Dry mix shotcretesuffers high dust generation and rebound lossesvarying from about 15 percent to up to 50percent. Wet mix shotcrete must contain enoughwater to permit pumping through the deliveryline. Wet mix shotcrete, as a result, mayexperience significantly more cracking problemsdue to the excess water and drying shrinkage. Advances in the development of the high rangewater reducing admixtures, pumping aids, andconcrete pumping equipment since about 1960have greatly reduced these problems, and wetmix shotcrete is now being used more frequentlyin repair construction.

Shotcrete is a very versatile construction materialthat can be readily placed and successfully usedfor a variety of concrete repair applications. Thenecessity of form work can be eliminated inmany repair applications by use of shotcrete. Shotcrete has been used to repair canal andspillway linings and walls, the faces of dams,tunnel linings, highway bridges and tunnels,deteriorating natural rock walls and earthenslopes, and to thicken and strengthen existingconcrete structures. Provided the propermaterials, equipment, and procedures areemployed, such shotcrete repairs can beaccomplished quickly and economically. Thisapparent ease of application should not cause oneto believe that shotcrete repair is a simpleprocedure or one that can be haphazardly orimproperly applied


54

Figure 43.—Dry mix shotcrete equipment being used in the Denverconcrete laboratories.

Figure 44.—Dry mix shotcrete equipment showing the nozzleand water injection ring.


55

Figure 46.—Wet mix shotcrete is propelled by compressed air.

Figure 45.—Wet mix shotcrete equipment. The premixed shotcrete is deliveredto the shotcrete pump by a transit truck.


56

with impunity. The following two paragraphscontain a very descriptive warning of suchpractices:

"Regardless of the considerable ad-vantagesof the shotcrete process and its ability toprovide finished work of the highest quality, alarge amount of poor and sometimesunacceptable work has unfortunately occurredin the past, with the result that many designand construction professionals are hesitant toemploy the process. As with all constructionmethods, failure to employ proper procedureswill result in inferior work. In the case ofshotcrete the deficiencies can be severe,requiring complete removal and replacement.

“Deficiencies in shotcrete applicationsusually fall into one of four categories:failure to bond to the receiving substrate,delamination at construction joints or facesof the application layers, incomplete filingof the material behind the reinforcing, andembedment of rebound or otherunsatisfactory material." (Warner, 1995).

Each of the above-listed deficiencies hasoccurred on Reclamation repair projects. Perhaps more important with shotcrete than withany other standard concrete repair method, ifhighly qualified, well trained, and competentworkmen cannot be employed, it is advisable toconsider using some other repair procedure. The quality of shotcrete closely depends uponthe skill and experience of one person, thenozzleman. Reclamation specifications requireemployment of only formally certifiednozzlemen for shotcrete repairs. The on-the-jobtraining necessary to develop the experience andskill needed to achieve such certification forReclamation work should occur prior to thenozzleman's arrival at the job.

(a) Preparation.—Concrete to be repaired withshotcrete should be prepared in a manneridentical to the preparation required forreplacement concrete, section 29.(a). Experience indicates, however, that surfacepreparation for shotcrete repair is more criticalthan for replacement concrete. It is essential

with shotcrete repairs that the shotcrete have aclean, sound concrete base for bond.

(b) Materials.—Cement used for shotcreteshould meet the same requirements as cementused for replacement concrete, section 29.(b). If sulfate exposure conditions exist, type Vportland cement should be specified. Normally,however, type I-II, low alkali cement isadequate. Water, sand, and coarse aggregateused in shotcrete should also meet therequirements for replacement concrete, exceptthat the maximum size coarse aggregate shouldnot exceed 3/8 of an inch.

Additives for shotcrete should meet therequirements of ASTM designation C 494,Chemical Admixtures for Concrete. It isnormally not possible to accomplish airentrainment with dry mix shotcrete. Lack of airentrainment may lead to dry mix shotcretehaving lower than desired freeze-thawresistance. Wet mix shotcrete should beproportioned to contain 6 to 8 percent entrainedair.

It is sometimes desirable to use acceleratingadmixtures in shotcrete where rapid setting or rapid strength development is required. Calcium chloride accelerators have long beenused, but there are now sufficient non-chloridecontaining accelerators in the market- place tomake the use of calcium chloride inadvisable. The use of calcium chloride accelerators isparticularly unadvisable in shotcreteapplications containing reinforcing steel or steelfibers.

Fiber reinforcement has been used in shotcretesince the early 1970s, and the M-47specifications in appendix A containspecifications for steel fiber reinforcement. TheAmerican Concrete Institute has published astate of the art report on fiber reinforcedshotcrete (American Concrete Institute, 1984),and this document should be consulted if theuse of fiber reinforced shotcrete is beingconsidered. It should be recognized that


57

application of fiber reinforced shotcrete is moredifficult and requires more experiencednozzlemen.

(c) Application.—The detailed discussion ofshotcrete application techniques and technologyis beyond the scope of this guide. TheAmerican Concrete Institute has published a recommended practice and aspecification for materials, proportioning, andapplication of shotcrete (American ConcreteInstitute, 1966; 1977). These documents shouldbe studied before attempting shotcrete repairs.

(d) Curing.—Proper curing of shotcrete isessential if high strength properties, durability,and long service life are to be obtained. The M-47 specifications permit water curing or curingof shotcrete by application of curingcompounds. It is important to begin curing byapplying approved curing compounds or waterspray before there has been evaporative waterloss from the shotcrete, particularly duringperiods of high temperatures, low humidity, orhigh wind conditions. Improvements in bondstrength will be obtained by continuing curingfor periods of up to a month.

29. Replacement Concrete.—Concrete repairsmade by bonding new concrete to repair areaswithout use of an epoxy bonding agent or mortargrout applied on the prepared surface should bemade when the area exceeds 1 square foot andhas a depth greater than 6 inches and when therepair will be of appreciable continuous area. Replacement concrete repairs should also beused for:

C Holes extending entirely through concretesections

C Holes in which no reinforcement isencountered, or in which the depth extends1 inch below or behind the backside of thereinforcing steel and which are greater inarea than 1 square foot and deeper than 4inches, except where epoxy- bondedconcrete replacement is required orpermitted as an alternative to concretereplacement

C Holes in reinforced concrete greater thanone-half square foot and extending beyondreinforcement

Replacement concrete is the most commonconcrete repair material and will meet the needsof a majority of all concrete repairs. Replacement concrete repairs are made bybonding new concrete to the repair areaswithout the use of a bonding agent or portlandcement grout. The combination of a deep repairand good curing practices ensures adequatehydration water will remain at the bondingsurface zone for at least 28 days, allowing thecement hydration process to develop good bond. Because the defective concrete is beingreplaced with high quality concrete very similarto the surrounding concrete, the repair iscompatible in thermal expansion and in otherphysical and chemical properties with the oldconcrete. For this reason, in many cases, thebest repair method is the use of replacementconcrete. Only when an unusual increase indurability is needed,or when placing conditions or dimensionsdictate otherwise, should other materials beconsidered.

(a) Preparation.—To obtain satisfactory resultswith the replacement concrete method,preparation should be as follows:

C Reinforcement bars should not be leftpartially embedded; concrete should beremoved to provide a clearance of at leastan inch around each bar exposed more thanone-third its circumference.

C The perimeter of the hole at the face shouldbe saw cut to a minimum depth of 1 inch. If the shape of the defect makes itadvisable, the remainder of the concreteremoval may be chipped below the verticalsaw cut and continued until a horizontalsurface is obtained. The top of the hole, ifon a vertical wall, should be cut on a 1:3upward slope from the back toward theface from which the concrete will beplaced (see figure 14). This is essential topermit vibration of the concrete without


58

leaving air pockets at the top of the repair. In some instances, where a hole extendsthrough a wall or beam, it may be necessaryto fill the hole from both sides; the slope ofthe top of the cut should be modifiedaccordingly.

C The bottom and sides of the hole should becut sharply and approximately square withthe face of the wall. When the hole extendsthrough the concrete section, spalling andfeather edges must be avoided by havingperimeter saw cuts from both faces. Allinterior corners should be rounded to aminimum radius of 1 inch.

C For repairs on surfaces subject todestructive water action and for otherrepairs on exposed surfaces, the outlines ofareas to be repaired should be saw cut asdirected to a depth of 1-1/2 inches beforethe defective concrete is excavated. Thenew concrete should be secured by keyingmethods. Figure 47 shows a vertical wallbeing prepared for replacement concreterepairs.

The construction and setting of forms areimportant steps in the procedure for satisfactoryconcrete replacement where the concrete mustbe placed from the side of the structure. Formdetails for walls are shown in figure 48. Toobtain a tight and acceptable repair, thefollowing requirements must be observed:

C Front forms for wall repairs more than18 inches high should be constructed inhorizontal sections so the concrete can beconveniently placed in lifts not more than12 inches deep. The back form may bebuilt in one piece. Sections to be set asconcreting progresses should be fittedbefore placement is started.

C To exert pressure on the largest area ofform sheathing, tie bolts should passthrough wooden blocks fitted snuglybetween the walers and the sheathing.

C For irregularly shaped holes, chimneys may

be required at more than one level; whenbeam connections are required, a chimneymay be necessary on both sides of the wallor beam. For such construction, thechimney should extend the full width ofthe hole.

C Forms should be substantially constructedso that pressure may be applied to thechimney cap at the proper time.

C Forms must be mortar tight at all jointsbetween adjacent sections, between theforms and concrete, and at tie bolt holes toprevent the loss of mortar when pressure isapplied during the final stages ofplacement. Twisted or stranded caulkingcotton, folded canvas strips,or similar material should be used as theforms are assembled.

Surfaces of old concrete to which new concreteis to be bonded must be clean, rough, and in asaturated surface dry condition. Extraneousmaterial on the joint resulting from formconstruction must be removed prior toplacement.

(b) Materials.—Concrete for repair should havethe same water-cement ratio as used for similarnew structures but should not exceed 0.47, byweight. Aggregate of as large a maximum sizeand slump as low as is consistent with properplacing and thorough vibration should be usedto minimize water content and consequentshrinkage. The concrete should contain 3 to 5percent entrained air. Where surface color isimportant, the cement should be carefullyselected or blended with white cement to obtainthe desired results. To minimize shrinkage, theconcrete should be as cool as practicable whenplaced, preferably at about 70 °F or lower. Materials should, therefore, be kept in shadedareas during warm weather. Use of ice inmixing water may sometimes be necessary. Batching of materials should be by weight; butbatch boxes, if of the exact size needed, may beused. Since batches for this class of work willbe small, the uniformity of the materials isimportant and should receive proper attention.


59

Figure 47.—Preparation of a wall for placement of replacement concrete repairs.


60

Figure 48.—Detail of forms for concrete replacement in walls.

Best repairs are obtained when the lowestpracticable slump is used. This is about3 inches for the first lift in an ordinary largeform. Subsequent lifts can be drier, and the topfew inches of concrete in the hole and that in thechimney should be placed at almost zero slump. It is usually best to mix enough concrete at thestart for the entire hole. Thus, the concrete willbe up to 1-1/2 hours old when the successivelifts are placed. Such premixed concrete,provided it can be vibrated satisfactorily, willhave less settlement, less shrinkage, and greaterstrength than freshly mixed concrete.

Structural concrete placements should be startedwith an oversanded mix containing about a 3/4-inch-maximum size aggregate; a maximum

water-cement ratio of 0.47, by weight; 6 percenttotal air, by volume of concrete; and having amaximum slump of 4 inches. This special mixshould be placed several inches deep on thejoint at the bottom of the placement. A mortarlayer should not be used on the constructionjoints.

(c) Application.—When placing concrete inlifts, placement should not be continuous; aminimum of 30 minutes should elapse betweenlifts. When chimneys are required at more thanone level, the lower chimney should be filledand allowed to remain for 30 minutes betweenlifts. When chimneys are required on both facesof a wall or beam, concrete should be placed inonly one of the chimneys until it flows to the


61

other. Attempted placement in both chimneyswill result in air entrapment and/or voids in thestructure.

The quality of a repair depends not only on useof low-slump concrete, but also on thethoroughness of the vibration during and afterdepositing the concrete. There is little danger ofovervibration. Immersion-type vibrators shouldbe used if accessibility permits. If not, this typeof vibrator can be used very effectively on theforms from the outside. Form vibrators can beused to good advantage on forms for largeinaccessible repairs, especially on a one-pieceback form, or attached to large metal fittingssuch as hinge-base castings. Immediately afterthe hole has been completely filled, pressureshould be applied to the fill and the formvibrated. This operation should be repeated at30-minute intervals until the concrete hardensand no longer responds to vibration. Pressure isapplied by wedging or by tightening the boltsextending through the pressure cap (figure 48). In filling the top of the form, concrete to a depthof only 2 or 3 inches should be left in thechimney under the pressure cap. A greaterdepth tends to dissipate the pressure. After thehole has been filled and the pressure cap placed,the concrete should not be vibrated without asimultaneous application of pressure. To do somay pro-duce a film of water at the top of therepair that will prevent bonding.

Addition of aluminum powder to concretecauses the latter to expand as described insection 182 of the Concrete Manual (Bureau ofReclamation, 1975). Under favorableconditions, this procedure has been successfullyused to secure tight, well-bonded repairs inlocations where the replacement material had tobe introduced from the side. Forms similar tothose shown in figure 48 should be used. Timeshould not be allowed for settlement betweenlifts. When the top lift and the chimney arefilled, no pressure need be applied, but thepressure cap should be secured in position soexpanding concrete will be confined to andcompletely fill the hole undergoing repair.There should be no subsequent revibration.

Concrete replacement in open-top forms, asused for reconstruction of the tops of walls,piers, parapets, and curbs, is a comparativelysimple operation. Only such materials as willmake concrete of proved durability should beused. The water-cement ratio should not exceed0.47, by weight. For the best durability, themaximum size of aggregate should be thelargest practicable and the percentage of sandthe minimum practicable. No special featuresare required in the forms, but they should bemortar tight when vibrated and should give thenew concrete a finish similar to the adjacentareas. The slump should be as low aspracticable, and dosage of air entraining agentshould be increased as necessary to secure themaximum permissible percentage of entrainedair, despite the low slump. Top surfaces shouldbe sloped to provide rapid drainage. Manipula-tion in finishing should be held to a minimum,and a wood-float finish is preferable to asteel-trowel finish. Edges and corners shouldbe tooled or chamfered. Use of water forfinishing is prohibited.

Forms for concrete replacement repairs usuallymay be removed the day after casting unlessform removal would damage the green concrete,in which event stripping should be postponedanother day or two. The projections left by thechimneys normally should be removed thesecond day. If the trimming is done earlier, theconcrete tends to break back into the repair. These projections should always be removed byworking up from the bottom because workingdown from the top tends to break concrete outof the repair. The rough area resulting fromtrimming should be filled and stoned to producea surface comparable to that of surroundingareas. Plastering of these surfaces should neverbe permitted.

Some replacement concrete does not requireforms. Replacement of damaged or deterioratedpaving or canal lining slabs, wherein the fulldepth of the slab is replaced, involvesprocedures no different from those required forbest results in original construction. Contactedges at the perimeter should be saw cut cleanand square with the surface.


62

Special repair techniques are required forrestoration of damaged or eroded surfaces ofspillway or outlet works tunnel inverts andstilling basins. In addition to the usual forces ofdeterioration, such repairs often must withstandenormous dynamic and abrasive forces fromfast-flowing water and sometimes fromsuspended solids. Silica fume concrete (section37) is the repair material of choice for thesetypes of repair. Whenever practicable, lowslump silica fume concrete should be used. Slump of the concrete should not exceed 2inches for slabs that are horizontal or nearlyhorizontal and 3 inches for all other concrete. (Note: This is 1 inch less slump than thatpermitted in the M-47 specifications forconventional applications of silica fumeconcrete.) The net water-cementitious ratio(exclusive of water absorbed by the aggregates)should not exceed 0.35 by weight. An air-en-training agent and a high range water reducingadmixture should be used. Set- retardingadmixtures should be used only when theinterval between mixing and placing is quitelong. (These recommendations are repeated insection 37.)

If, however, needed repairs are too small for thereplacement concrete method (including silicafume concrete), they should be made using thedry pack procedure (section 26), theepoxy-bonded epoxy mortar method, (section30) or the epoxy-bonded replacement concretemethod (section 31).

(d) Curing and Protection.—The importance ofcuring replacement concrete repairs cannot beoveremphasized. Complete failure of repairshas been attributed to inadequate or impropercuring. There is no known condition short offlooding the repaired structure (which in itself isan excellent curing method) that does notrequire curing of cementitious repairs. Becauseof the relatively small volume of most repairsand the tendency of old concrete to absorbmoisture from new material, water curing is ahighly desirable procedure, at least during thefirst 24 hours. When forms are used for repair,they can be removed and then reset to hold afew layers of wet burlap in contact with new

concrete. One of the best methods of watercuring is a soil- soaker hose laid beneath aplastic membrane covering the repair area.

When curing compound is used, the best curingcombination is an initial water-curing period of7 days (never less than 24 hours) followed,while the surface is still damp, by a uniformcoat of the compound. It is always essential thatrepairs, even dry packed cone bolt holes,receive some water curing and be thoroughlydamp before the curing compound is applied. Ifnothing better can be devised for the initialwater curing of the dry pack in cone bolt holesand similar repairs, a reliable workman shouldbe detailed to make the rounds with water and alarge brush or a spraying device to keep the re-paired surfaces wet for 24 hours prior toapplication of a curing compound. Whitecuring compound may be used only where itscolor does not create objectionable contrast inappearance.

30. Epoxy-Bonded Epoxy Mortar.— Epoxy-bonded epoxy mortar should be used where thedepth of repair is less than 1-1/2 inches and theexposure conditions are such that relativelyconstant temperatures can be expected. Epoxymortars have thermal coefficients of expansionthat may be significantly different fromconventional concrete. If such mortars are usedunder conditions of wide and frequenttemperature fluctuations, they will cause failurejust below the bond surface in the baseconcrete. For this reason, current Reclamationpractice precludes the use of epoxy mortarsunder conditions of frequent or largetemperature fluctuations.

The application of epoxy mortar to repair areasof concrete deterioration caused by corrodingreinforcing steel is also not recommended. Theepoxy bond coat and epoxy mortar create zonesof electrical potential that are different from theelectrical potential in the surrounding concrete. This difference in potential can result in theformation of a galvanic corrosion cell withaccelerated corrosion at the repair perimeters.


63

Epoxy mortar is properly used to make thinrepairs (1/2-inch to 1-1/2-inch thickness) toconcrete under relatively constant temperatureexposure conditions. Such applications couldinclude tunnel linings, indoor or interiorconcrete, the underside of concrete structuressuch as bridge decks, continuously inundatedconcrete such as stilling basin floors, canallinings below water line, or concrete pipe. Applications to concrete exposed to the dailytemperature fluctuations caused by exposure todirect sunlight are not appropriate for epoxymortar repair.

Properly applied epoxy mortar repairs have along history of successful performance onReclamation concrete when used underappropriate conditions. A 1991 inspection ofthe epoxy mortar repairs made at YellowtailDam in 1968 showed that less than 2 percent ofthe repairs had suffered failure in over 20 years of service. This is considered out-standing performance for a repair material.

(a) Preparation.—Concrete to be repaired withepoxy mortar should be prepared in accordancewith section 8. Prior to application of the epoxymortar, the concrete should be heated insufficient depth, when necessary, so that thesurface temperature (as measured by a surfacetemperature gage) does not drop below 40 EFduring the first 4 hours after placement of anepoxy bond coat. This may require severalhours of preheating with radiant heaters or otherapproved means (figures 49 and 50). If existingconditions prohibit meeting these temperaturerequirements, suitable modifications should beadopted upon the approval of the inspector orother responsible official. The concretetemperature during preheating should neverexceed 200 EF, and the final surfacetemperature at the time of placing epoxymaterials should never be greater than 100 EF.

(b) Materials.—Epoxy resins used to prepareepoxy mortar for use in concrete repair shouldbe two-component, 100-percent solids typemeeting the requirements of specificationASTM C-881 for type III, grade 2, class B or C.

Class B epoxy is used between 40 and 60 EF. Class C epoxy is used above 60 EF up to thehighest temperature defined by the epoxymanufacturer. The sand used in epoxy mortarmust be clean, dry, well graded, and composedof sound particles. For most applications, sandpassing a No. 16 screen and conforming to thefollowing limits should be used:

Screen number

Individual percent,by mass, retained on

screen

30 26 to 36

50 18 to 28

100 11 to 21

Pan 25 to 35

Range shown is applicable when 60 to 100percent of pan is retained on No. 200 screen. When 41 to 100 percent of pan passes the No.200 screen, the percent pan should be within therange of 10 to 20 percent, and the individualpercentages retained on the Nos. 30, 50, and100 screens should be adjusted accordingly.

Sand processed for use in concrete rarelycontains the required quantity of pan size sand. As a result, problems often arise in obtainingadditional pan size material to supplement sandavailable on the jobsite. A source of silica pansize material may be obtained by contacting theMaterials Engineering and ResearchLaboratory, Code D-8180, Bureau ofReclamation, Denver Federal Center, Denver,Colorado 80225. A sand graded as shownabove and properly mixed with an epoxymeeting ASTM C-881 specifications willprovide a dense, high strength, workable epoxymortar.


64

Figure 50.—An enclosure has been constructed over an area to be repaired withepoxy mortar to keep the concrete warm.

Figure 49.—A gas-fired forced air heater is being used to heat concreteprior to application of epoxy mortar.


65

The sand should be maintained in a dry area at notless than 70 EF for 24 hours immediately prior tothe time of use. Filler materials other than sand,such as portland cement, can be used. However,for general applications, a natural sand isrecommended.

It is also acceptable to obtain and use brand nameprepackaged epoxy mortar repair systems thatcontain resin and sand, provided that the resinsystems meet the ASTM C-881 specificationspreviously listed. Such mortar systems aremanufactured specifically for concrete repair andmust be used in exact accordance with themanufacturer's recommendations.

On critical repair jobs such as areas of high velocityflow or on repairs requiring a considerable quantityof materials, the contractor should be required tosubmit samples of epoxy resin and graded sand tothe Materials Engineering and ResearchLaboratory, Denver, for use in mix designdeterminations. The samples should consist of 1gallon total quantity of epoxy components and aminimum of 50 pounds of graded sand. Samplesshould be submitted at least 30 days prior to use inthe work and be labeled or otherwise identifiedwith the specifications number under which thematerial is to be used.

(c) Mixing.—Preparation of epoxy mortarinvolves premixing proper quantities of epoxy resinand hardener and then mixing the resin system withsand to make the epoxy mortar.

The epoxy resin used for mortar preparation is atwo-component (part A and part B) material whichrequires accurate combination of components andmixing prior to use. Once mixed, the material has alimited pot life and must be used immediately. (Potlife refers to the period of time elapsing betweenmixing of ingredients and their stiffening to thepoint where satisfactory use cannot be achieved.) The repair resin should be prepared by adding therequired quantity of hardener (normally, part B) tothe resin (normally part A) in proportionsrecommended by the manufacturer, followed bythorough mixing. Since the pot life of the mixturedepends on the temperature (longer at lowtemperature, much shorter at high temperature), thequantity to be mixed at one time should be thatquantity that can be applied within approximately 30 minutes. The addition of nonreactive thinners or

diluents to the resin mixture is not permitted sinceit weakens the epoxy.

The epoxy mortar is composed of sand and epoxyresin suitably blended to provide a stiff, workablemix. Mix proportions should be established,batched, and reported on a weight basis, althoughthe dry sand and mixed epoxy may be batched byvolume using suitable measuring containers thathave been calibrated on a weight basis. Epoxymeeting ASTM specification C-881 will requireapproximately 5-1/2 to 6 parts of graded sand to 1part epoxy, by weight. This is equivalent to a ratioof approximately 4 to 4-1/2 parts sand to 1 partepoxy, by volume. If equivalent volumeproportions are being used, care must be taken toprevent confusing them with weight proportions. Itwill be necessary to adjust the mix proportions forthe particular epoxy and sand being used. Theepoxy mortar should be thoroughly mixed with aslow-speed mechanical device. The mortar shouldbe mixed in small size batches so that each batchcan be completely mixed and placed withinapproximately 30 minutes. Figure 51 shows asimple bucket mixer that is adequate to mix epoxymortar for small repairs.

(d) Application.—Application of epoxy mortarrepairs first requires application of a resin bondcoat followed by application and finishing of theepoxy mortar. Surfaces of existing concrete towhich epoxy mortar is to be bonded should beprepared as discussed in section 8. Steel to beembedded in epoxy mortar should be prepared,cleaned, and dried in the same manner as theconcrete being repaired. The exposed steel shouldbe completely coated with epoxy bonding agentwhen the agent is applied to the surfaces of therepair area.

A resin bond coat consisting of the same typeepoxy resin used to mix the epoxy mortar is appliedto the prepared concrete surface immediatelybefore placing the epoxy mortar. After the bondcoat resin is mixed, it must be uniformly applied tothe prepared, dry, existing concrete at a coverage ofnot more than 80 square feet per gallon, dependingon surface conditions. The area of coverage pergallon of resin depends on the roughness of thesurface to be covered and may be considerably lessthan the maximum specified. The epoxy bondingagent may be applied by any convenient, safemethod such as


66

Figure 51.—A bucket mixer can be used to mix epoxy mortar for small repair areas.


67

squeegee, brushes, or rollers which will yield aneffective coverage. Spraying of the material ispermitted if an efficient airless spray is used andif the concrete surfaces to receive the agent areat a temperature of 70 EF or some-what warmer. Before approving spraying, it should bedemonstrated that spraying will provide anadequate job with minimum overspray. If sprayapplication is used, the operator must wear acompressed air-fed hood, and no otherpersonnel should be closer than 100 feet ifdownwind of the operator.

During application of the epoxy bond coat, caremust be exercised to confine the material to thearea being bonded and to avoid contaminationof adjacent surfaces. However, the bond coatshould extend slightly beyond the edges of therepair area.

The applied epoxy bonding resin must be in afluid condition when the epoxy mortar is placed. If the resin cures beyond this fluid state but isstill tacky, a second bond coat should be appliedover the first coat. If any bond coat has curedbeyond the tacky state, it must be completelyremoved by sandblasting, the concrete properlycleaned, and a new bond coat applied.

Special care must be taken to prevent the bondcoat from being spread over concrete surfacesnot properly cleaned and prepared.

Appropriate solvents may be used to clean toolsand spray guns, but in no case should thesolvents be incorporated in any bonding agent. All tools must be completely dried before reuse.

The prepared epoxy mortar should be tamped,flattened, and smoothed into place (figure 52) inall areas while the bonding resin is still in afluid condition, except that on steep slopes, thebond coat can be allowed to stiffen to a verytacky condition to assist in holding the mortar inplace. Special care must be taken to thoroughlycompact the epoxy mortar against the bond coat. The mortar should be worked to grade and givena steel trowel finish (figure 53). Special caremust be taken at the edges of the area beingrepaired to assure complete filling and leveling

and to prevent the mortar from being spreadover surfaces not having the epoxy bond coatapplication. Steel troweling should best suitprevailing conditions; in general, it should beperformed by applying slow, even strokes. Trowels may be heated to facilitate thefinishing, but the use of thinner, diluents, water,or other lubricants on placing or finishing toolsis not permitted. After leveling the epoxymortar to the finished grade where precisionsurfaces are required on sloping, vertical, oroverhead surfaces, the mortar should be coveredwith plywood panels smoothly lined withpolyethylene sheeting and weighted withsandbags or otherwise braced by suitable meansuntil the possibility of slumping has passed. When polyethylene sheeting is used, no attemptshould be made to remove it from the epoxymortar repair before final hardening.

Surfaces of all epoxy mortar repairs should befinished to the plane of surfaces adjoining therepair areas. The final finished surfaces shouldhave the same smoothness and texture ofsurfaces adjoining the repair areas.

(e) Curing.—Epoxy mortar repairs should becured immediately after completion at not lessthan the temperature range prescribed by theclass of the epoxy until the mortar is hard. Postcuring, if required by the specifications, canthen be initiated at elevated temperatures byheating in depth the epoxy mortar and theconcrete beneath the repair. Postcuring shouldcontinue for a minimum of 4 hours at a surfacetemperature generally not less than 90 EF nor more than 110 EF. The heat could besupplied by use of portable propane-firedheaters, infrared lamp heaters, or otherapproved sources positioned to attain therequired surface temperatures (figure 54).

In no case should epoxy-bonded epoxy mortarbe subjected to moisture until after the specifiedpostcuring has been completed.

Epoxy mortars generally produce patches thatare darker than the surrounding concrete.


68

Figure 52.—Epoxy mortar is consolidated and compacted by hand tamping.

Figure 53.—Applying the steel trowel finish required by epoxy mortar repairs.


69

Figure 54.—Postcuring heating enclosure installed over an epoxy mortar repair area.

Some available epoxies produce a gray- coloredmortar resembling concrete. However, thesematerials will rarely produce an exact colormatch. Grinding hardened epoxy mortar maylighten its color to about that of the surfacesadjoining the repair areas. Epoxy mortars canbe colored by the addition of such materials asiron oxide red, chromium oxide green,lampblack and titanium dioxide white for gray,and ocher yellow; although Reclamation rarelyuses any materials to color the epoxy other thanthe sand for the mortar. Use of white silica sandin the mortar will produce a white-lookingpatch; most natural riverborne sands willproduce darker colored mortars. Wheneverepoxy mortar repair materials must be colored tomatch adjacent concrete, laboratory mixesshould be made to ascertain the properquantities of coloring constituents.

(f) Safety.—All personnel must be carefullyinstructed to take every precaution in pre-venting epoxy resins and their components fromcontacting the skin and in preventing thebreathing of epoxy fumes or vapors. Protec-tiveclothing must be worn, including gloves andgoggles, and protective creams for otherexposed skin areas should be provided when

handling epoxies, as severe allergic reactionsand possible permanent health damage canresult when these materials are allowed to con-tact and remain upon the skin. Any depositsacquired through accidental contact of thesematerials with unprotected skin must beremoved immediately by washing with soap andwater, never with solvents. Solvents, such astoluene and xylene, may be used only forcleaning epoxy from tools and equipment. Caremust also be exercised to avoid contact ofcleaning solvents with the skin and to provideadequate ventilation for mixing, placing, andcleanup operations. All safety equipment usedmust conform to the requirements of theOccupational Safety and Health Standards ofthe Occupational Safety and HealthAdministration.

31. Epoxy-Bonded Replacement Concrete.—Epoxy-bonded concrete is used for repairs toconcrete that are between 1.5 and 6 inchesthick. Shallow replacement concrete repairs,less than 6 inches thick, are subject to poorcuring conditions as a result of moisture loss toevaporation and to capillary absorption by theold base concrete. Such repairs seldom developacceptable bond strength to the old concrete.


70

The epoxy bonding resin is used to ensure astrong, durable bond between the old concreteand the replacement concrete.

As with epoxy-bonded epoxy mortar, careshould be exercised if epoxy-bonded concrete isto be used to repair shallow deteriorationresulting from corroding reinforcement. Theepoxy bond coat may create electrical potentialssufficiently different from potentials in thesurrounding concrete to result in acceleratedcorrosion at repair perimeters.

(a) Preparation.—Concrete to be repaired withepoxy-bonded concrete must be prepared asdescribed in section 8.

(b) Materials.—The materials used in epoxy-bonded concrete repairs consist of conventionalportland cement concrete and epoxy resinbonding agent.

The concrete used for epoxy-bonded repairs isthe same as that used for replacement concreterepairs (section 29) except that the slump of theconcrete when placed should not exceed 1-1/2 inches.

A number of proprietary epoxy formulationsprepared for bonding new concrete to oldconcrete are now available. Many of thesematerials are excellent high quality products andcan be used with reasonable certainty as to theresults. However, some of the resins availableare unsuitable or untested for such repairapplications, and care should be taken to useonly the epoxy bonding resins meeting therequirements of specification ASTM C-881 fora type II, grade 2, class B or C epoxy system. Class B epoxy should be used when thetemperatures are above 40 EF but less than 60EF. Class C epoxy should be used whenconcrete temperatures are from 60 EF up to themaximum temperature recommended by theepoxy manufacturer.

The epoxy resin used for epoxy-bonded concreteis a two component, 100-percent solids resinsystem requiring accurate proportioning andthorough mixing prior to use. The procedures

described in section 30 should be followedduring preparation and application of the resin. Conventional concrete mixing procedures asdescribed in section 29 should be followed tomix the concrete.

(c) Application.—Use of epoxy-bondedconcrete in repairs requiring forming, such ason steeply sloped or vertical surfaces, can bepermitted only when sufficient time has beenallowed to place concrete against the epoxybonding resin while it is still fluid. If the resincures before placement of the concrete, no bondwill develop between the old and new concrete. It is a good idea to practice install such forms atleast once before actually applying the epoxybond coat (figure 55).

Immediately after application of the epoxy resinbonding agent and while the epoxy is still fluid,unformed epoxy-bonded concrete should bespread evenly to a level slightly above gradeand compacted thoroughly by vibrating ortamping (figure 56). Tampers should besufficiently heavy for thorough compaction. After being compacted and screeded, theconcrete should be given a wood-float orsteel-trowel finish as required. Water, cement,or a mixture of dry cement and sand shouldnever be sprinkled on the surface. Troweling, ifrequired, should be performed at the propertime and with heavy pressure to produce asmooth, dense finish free of defects andblemishes. As the concrete continues to harden,the surface should be given additionaltrowelings.

The final troweling should be performed afterthe surface has hardened so that no cementpaste will adhere to the edge of the trowel, butexcessive troweling cannot be permitted.

(d) Curing.—Even though an epoxy bond coatis used, it still remains essential to properly cureepoxy-bonded concrete. As soon as theepoxy-bonded concrete has hardenedsufficiently to prevent damage, the surfaceshould be cured by spraying lightly with waterand then covering with sheet poly-ethylene orby coating with an approved curing compound.


71

Figure 55.—If forms are required for epoxy-bonded concrete repairs, they should be installedat least once prior to application of the epoxy bond coat to ensure that they fit as planned

and that they can be installed and filled before the bond coat hardens.


72

Figure 56.—The placement techniques for epoxy-bonded concrete are essentiallythe same as for conventional concrete.

Curing compound should be used wheneverthere is any possibility that freezingtemperatures will prevail during the curingperiod. Sheet polyethylene must be an airtight,nonstaining, waterproof covering that willeffectively prevent evaporation. Edges of thepolyethylene should be lapped and sealed. Thewaterproof covering should be left in place forat least 2 weeks. If a waterproof covering isused and the concrete is subjected to any usageduring the curing period that might rupture orotherwise damage the covering, the coveringmust be protected by a suitable layer of clean,wet sand or other cushioning material that willnot stain concrete. Application of curingcompound must be in accordance withappropriate standard procedures as contained inthe Concrete Manual (Bureau of Reclamation,1975).

(e) Safety.—All personnel must be carefullyinstructed to take every precaution in preventingepoxy resins and their components fromcontacting the skin and in preventing thebreathing of epoxy fumes or vapors. Protectiveclothing must be worn, including gloves and

goggles, and protective creams for otherexposed skin areas should be provided whenhandling epoxies, as severe allergic reactionsand possible permanent health damage canresult when these materials are allowed to con-tact and remain upon the skin. Any depositsacquired through accidental contact of thesematerials with unprotected skin must beremoved immediately by washing with soap andwater, never with solvents. Solvents, such astoluene and xylene, may be used only forcleaning epoxy from tools and equipment. Caremust also be exercised to avoid contact ofcleaning solvents with the skin and to provideadequate ventilation for mixing, placing, andcleanup operations. All safety equipment usedmust conform to the requirements of theOccupational Safety and Health Standards ofthe Occupational Safety and HealthAdministration.

32. Polymer Concrete.—Polymer concrete(PC) is a concrete system composed of apolymeric resin binder and fine and coarseaggregate. Water is not used to mix polymerconcrete. Instead, the liquid resin, known as a


73

monomer, is caused to cure or harden by achemical reaction known as polymerization. During polymerization, the monomer moleculesare chemically linked and cross linked to form ahard, glassy plastic known as a polymer. Thepolymers used in PC are formulated to providethe special properties needed for highperformance repair materials. These systemscan be cured very quickly and are most useful inperforming repairs to structures that must beimmediately returned to service. As anexample, PC is commonly used to repairpotholes in concrete highway bridge decks,thereby eliminating the necessity of long andcostly road closures or detours. It is also usefulfor repairs to structures, such as tunnel linings,that can be maintained in a dry condition foronly short periods of time and for cold weatherrepairs down to temperatures as low as 15 EF. PC repairs can be accomplished in thicknessesvarying from about 1/2 inch to several feet ifappropriate precautions are taken.

PC develops strength and durability propertiesvery quickly due to its rapid polymerizationcharacteristics and is useful where rapid repairsto concrete are required. PC can be mixed,placed, polymerized, and put into service in onlya matter of hours. PC also develops enhanceddurability properties. This feature makes ituseful as protective overlays on conventionalconcrete exposed to corrosive or severeenvironments. Since PC does not contain mixwater, it can be used at much lowertemperatures (down to 15 EF) than portlandcement concrete.

Most polymer concretes experience somevolumetric shrinkage during polymerization andalso have problems associated with thecoefficient of thermal expansion similar to thoseexperienced with epoxy mortars. Theseproblems with PC, though generally less severethan similar problems with epoxy mortar, canlimit the materials use on concrete exposed towide temperature variations. Potential users ofPC should be aware of these problems. TheMaterials Engineering and Research Laboratoryat Denver, D-8180, can provide guidance andrecommendations for the application of these

very useful materials.

(a) Preparation.—Concrete preparation for PCrepairs should be in accordance with section 8. Although some manufacturers indicate that PCmay be used for feather edge repairs,Reclamation experience is otherwise. Saw cutrepair perimeters are required if high qualityrepairs are to be achieved. Special care shouldbe taken to ensure the base concrete is dry priorto application of the repair material. Once thePC is in place, this requirement can be relaxed. However, flowing water may remove the freshpolymer concrete if allowed on the concreteprior to development of initial set.

(b) Materials.—A number of manufacturershave developed prepackaged PC systems. Mostof the systems consist of acrylic or vinyl estermonomers, appropriate polymerization initiatorsand catalysts, and fine aggregate and fillers. Itis common for the user to extend the polymerconcrete, particularly when used to filldepressions deeper than 1 inch, by supplyingand adding coarse aggregate to the prepackagedPC system during mixing. The prepackagedpolymer concretes also contain monomer bondcoat systems that must be mixed and applied tothe base concrete prior to application of thepolymer concrete mixture.

(c) Application.—Each manufacturer ofprepackaged PC provides detailed instructionsfor proportioning, mixing, and applying itsproduct. These instructions must be closelyfollowed to obtain a satisfactory repair.

A bond coat monomer system is mixed andapplied to the prepared concrete prior toapplication of the PC. Care must be taken toproportion and mix the bond coat componentsproperly. Some manufacturers specify that thebond coat be applied and cured prior to placingthe polymer concrete. Others specify that thepolymer concrete be applied while the bondcoat is still in the liquid state. It is important tofollow the procedures recommended by themanufacturer of the product actually being used.


74

Polymer concrete can be mixed in paddle-type,rotary drum-type, or other types of powerequipment suitable for mixing conventionalconcrete. Very small quantities of PC can evenbe mixed in the original shipping containers. Three minutes of mixing time should beadequate for all the prepackaged systems. It iscommon practice to first add the dry powder andaggregate components to the mixer and then addthe liquid resin. With some systems, the liquidcomponent may require a separate premixingstep to combine the monomer with the catalystor initiators needed for polymerization. Othermanufacturers include the initiators in thepowder-fine aggregate component, therebyeliminating the premixing requirement.

The mixed PC is placed just like conventionalconcrete, using the same tools and procedures(figure 57). Most PC mixtures will be almost self-leveling and require only a minimumfinishing operation. Light mechanical vibrationshould be provided to consolidate placementsthicker than 2 to 3 inches (figure 58). Once thePC has been placed and consolidated, it shouldbe screeded to proper grade and quickly finishedwith a wood or steel trowel. The top surface ofthe repair forms a "skin" soon after beingplaced. If repeated toweling is attempted, thisskin will tear and cause an unsightly surface.

Polymer concrete develops a strong bond tomost materials. If forms are used, they must beleakproof and provided with some method ofbond breaker or release agent. Wrapping theforms with polyethylene film has proven a veryeffective method of preventing bond betweenthe form and the PC.

(d) Curing.—Polymer concretes polymerize andharden very quickly under most ambientconditions and will develop nearly full strengthwithin a 1- to 2-hour period. During this time,the fresh concrete must be protected from waterand not disturbed (figure 59). If temperaturesare lower than about 40 EF, the polymerizationreaction will occur at a slower rate unlessincreased concentrations of initiator are used orthe repair is heated to 70E to 80 EF. Conversely,polymerization can occur too quickly, with

insufficient finishing time, if the ambienttemperature exceeds 90E to 100 EF. Areduction of initiator concentration can reducethis problem. Alternately, the repairs can bemade during the cooler parts of the day or atnight.

(e) Safety.—All workers, supervisors, andinspectors involved with the project must bemade aware of the procedures required for safeuse of PC. The manufacturers of PC providerecommendations for safe storage, handling,and use. These recommendations must beknown and followed by users of the materials. The following minimum safety requirementsmust be followed on Reclamation projects:

Storage.—Polymer concrete monomer andinitiators are heat sensitive and flammable. These materials should be stored away from thedirect rays of sunlight, in the original shippingcontainers, in well-ventilated areas away fromsources of ignition. The storage temperatureshould not exceed 80 EF. Storage periodsshould not exceed manufacturer’srecommendations.

Mixing and Handling.—Smoking, flame, orother sources of ignition must not be permittedduring mixing and application. Electricalequipment in contact with polymer concreteshould be grounded for safe discharge of staticelectricity. Type B or type ABC fireextinguishers must be provided at the storage,mixing, and application locations.

Personal Protective Equipment.—Workersusing polymer concrete must be providedrubber boots and required to use disposableprotective clothing. Splash-type safety gogglesand impervious gloves must be provided toworkers using polymer concrete, and theworkers must be required to wear these items. In some instances where ventilation is poor orinadequate, workers may be required to wearorganic vapor respirators. The mixing andapplication site should be provided withportable eyewash equipment capable of


75

Figure 57.—Placing polymer concrete in a repair area. Sandbags and polyethylene sheetingwere used to prevent water from entering the repair area.


76

Figure 59.—Polymer concrete must be protected from water and not disturbed duringthe 1- to 2-hour curing period. No other curing procedures are required unlessambient temperatures are very low.

Figure 58.—Small stinger vibrators can be used to consolidate shallow depths ofpolymer concrete.


77

sustaining a 15-minute stream of clean, roomtemperature water.

33. Thin Polymer Concrete Overlay.—Thethin PC overlay is a hard, glassy concretecoating, 25 to 50 mils thick, consisting of avinyl ester resin system, silica flour filler, andappropriate coloring pigments. This membrane-forming overlay partially penetrates theimmediate top surface of the concrete andprovides very good protection to concreteexposed to adverse chemical or weatheringconditions. It can also provide cosmetictreatment to concrete exposed to public view. The normal three-coat application of thismaterial (one primer coat plus two filler coats)should result in a total overlay thickness ofabout 50 mils.

The overlay is applied to protect the concretefrom water penetration and resulting freeze-thaw damage; to protect the concrete fromchemical corrosive elements such as acids,chlorides, or sulfates; and/or to improve thecosmetic appearance of the concrete. Theoverlay provides complete opaque coverage ofthe concrete surface and flows into and sealsnarrow cracks in the surface. The thin PCoverlay is a standard repair material specified inthe Standard Specifications for the Repair ofConcrete, M-47 of appendix A. There iscurrently no known commercial manufacturer ofthe thin polymer concrete overlay. Contractorsor users of the overlay systemcan have the material prepared by custom resinblenders or can blend and mix the materialthemselves using the formulas listed below.

(a) Preparation.—Concrete to receive the thinpolymer concrete overlay must be cleaned andprepared using light hydroblasting or wetsandblasting in accordance with therequirements of section 8. The preparedconcrete surfaces must then be maintained in aclean, dry condition until the placement of thethin overlay is completed. The dryness of theconcrete can be checked by taping a clearpolyethylene sheet onto the surface of theconcrete in a sunlight exposure. If no moisturecollects under the polyethylene sheet after an

hour or two of sunlight, the surface issufficiently dry.

(b) Materials.—The thin overlay is preparedwith vinyl ester resin, polymerization initiatorand promoter, silicon flour filler, and pigments.

VinylEster.—The vinyl ester resin is Dow Derakane8084, manufactured by Dow Chemical Co.,2800 Mitchell Drive, Walnut Creek, California 94596.

Initiator.—The initiator is cumenehydroperoxide-78 percent, manufactured byLucidol Division, Penwalt Corp., 1740 MilitaryRoad, Buffalo, New York 14240, or equal.

Promoter.—The promoter is cobaltnapthenate-6 percent, available from fiber-glassmaterials suppliers.

Filler.—The filler is ground silica, minus 45 micrometers (No. 355) sieve size, manu-factured by Ottawa Silica Co., Ottawa, Illinois;or Silco Seal 395 Ground Silica, manu-factured by VWR Scientific, PO Box 3200,San Francisco, California 94119.

Pigment.—Two pigments are required toobtain a concrete gray color.

Titanium dioxide powder, manufacturedby VWR Scientific

Carbon lamp black or bone black powder(do not use activated carbon)

Mixing Proportions.—

Primer 5.00.600.25

gallons vinyl ester resinpounds initiatorpounds promoter

Pigmented topcoats

5.01.350.2740.04.00

0.02

gallons vinyl ester resinpounds initiatorpounds promoterpounds fillerpounds titanium dioxide pigmentpounds carbon black pigment


78

Mixing Sequence.—The vinyl ester resin,filler, and pigments should be premixed and setaside for several hours to wet out before use. Immediately prior to application, the initiator isadded and thoroughly mixed with the resin. Then, the promoter is added to the resin andthoroughly mixed. Never directly mix initiatorand promoter, or an extremely violent andexplosive reaction will occur.

(c) Application.—The thin polymer concreteoverlay consists of one primer coat and one ortwo sealant coats applied at a coverage rate of1.3 to 2.0 gallons of material per 100 square feetof surface per coat, depending on surfacetexture of the concrete. The material may beapplied with brooms, brushes, or paint rollers(figure 60).

The primer must uniformly and completelycover the surface and should be scrubbed intothe surface of the concrete, eliminating dis-continuities and puddles. The pigmented top-coat(s) must be applied to the primed surfacenot less than 4 hours nor more than 24 hoursafter application of the primer or of asucceeding to coat. It is not desired that theprimer or topcoat cure to a hard final finishbefore application of the succeeding topcoat. Asomewhat tacky finish is more desirable. However, full bond between coats will beobtained by following the above-listed time-frame for application.

Caution must be exercised to preventapplication of primer or topcoats not containinginitiator, promoter, or both. A simple techniqueof reducing the possibility of this is to placecontainers of preweighed resin, initiator, andpromoter at appropriate locations along theapplication route before the application begins. After the containers are preplaced, oneworkman can quickly check that all neededcomponents are at each location. Then, asapplicators need a resupply of the primer ortopcoating system, they need only to mix all thecontainers at the next location.

Application of the thin PC overlay systemproceeds quite quickly. By proper pre-planning,

two men were able to prime and topcoat the power house roof shown in fig-ure 61 in 2 days. (d) Curing and Protection.—The coatedsurfaces must be protected until the resin hascompletely cured to a hard finish. Suchcondition will normally be obtained withinabout 30 hours of application of the final top-coat. Low ambient temperatures and/or highrelative humidity may lengthen the hardeningprocess.

(e) Safety.—All workers, supervisors, andinspectors involved with the project must bemade aware of the procedures required for safeuse of the thin polymer concrete coating. Themanufacturers of vinyl ester resin and theinitiators and promoters providerecommendations for safe storage, handling,and use. These recommendations must beknown and followed by users of the materials. The following minimum safety requirementsmust be followed on Reclamation projects:

Storage.—Vinyl ester resin and initiators areheat sensitive and flammable. These materialsshould be stored away from direct sunlight, inthe original shipping containers, in well-ventilated areas away from sources of ignition. The storage temperature should not exceed 80EF. Storage periods should not exceedmanufacturer’s recommendations.

Mixing and Handling.—Smoking, flame, or other sources of ignition must not bepermitted during mixing and application. Electrical equipment in contact with polymerconcrete should be grounded for safe dischargeof static electricity. Type B or type ABC fireextinguishers must be provided at the storage,mixing, and application locations. Neverdirectly mix initiator and promoter, or anextremely violent and explosive reaction willoccur.

Personal Protective Equipment.—Workersusing thin polymer concrete overlays must beprovided rubber boots and required to usedisposable protective clothing. Splash-type


79

Figure 60.—The thin PC overlay system may be applied with push brooms, squeegees,or heavy industrial grade paint rollers.


80

Figure 61.—The thin PC overlay system can be applied very quickly. Twoworkmen completed application to this powerplant roof in 2 days.

safety goggles and impervious gloves must beprovided to workers using polymer concrete,and the workers must be required to wear theseitems. In some instances where ventilation ispoor or inadequate, workers may be required towear organic vapor respirators. The mixing andapplication site should be provided withportable eyewash equipment capable ofsustaining a 15-minute stream of clean, roomtemperature water.

34. Resin Injection.—Resin injection is used torepair concrete that is cracked or delaminatedand to seal cracks in concrete to water leakage. Two basic types of resin and injectiontechniques are used to repair Reclamationconcrete.

(a) Epoxy Resins – Epoxy resins cure to formsolids with high strength and relatively high moduliof elasticity. These materials bond readily toconcrete and are capable, when properly applied, ofrestoring the original structural strength to crackedconcrete. The high modulus of elasticity causesepoxy resin systems to be unsuitable for rebondingcracked concrete that will undergo subsequentmovement. Epoxy resin has been used to seal

cracks in concrete to waterflow. The epoxies,however, do not cure very quickly, partic-ularly atlow temperatures, and using them to stop largeflows of water may not be practical. Cracks to beinjected with epoxy resins should be between 0.005inch and 0.25 inch in width. It is difficult orimpossible to inject resin into cracks less than0.005 inch in width, while it is very difficult toretain injected epoxy resin in cracks greater than0.25 inch in width, although high viscosity epoxieshave been used with some success. Epoxy resinscure to form relatively brittle materials with bondstrengths exceeding the shear or tensile strength ofthe concrete. If these materials are used to rebondcracked concrete that is subsequently exposed toloads exceeding the tensile or shear strength of theconcrete, it should be expected that the cracks willrecur adjacent to the epoxy bond line. In otherwords, epoxy resin should not be used to rebond"working" cracks.

Epoxy resins will bond with varying degrees ofsuccess to wet concrete, and there are a number ofspecial techniques that have been developed andused to rebond and seal water leaking cracks withepoxy resins. These special techniques andprocedures are highly technical and, in most cases,


81

are proprietary in nature. They may haveapplication on Reclamation projects, but only aftera thorough analysis has been performed to ensurethat the more standard repair procedures will not besuccessful or cost effective.

(b) Polyurethane Resins.—Polyurethane resinsare used to seal and eliminate or reduce waterleakage from concrete cracks and joints. They canalso be injected into cracks that experience somesmall degree of movement. Such systems, with theexception of the two-part solid polyurethanes, haverelatively low strengths and should not be used tostructurally rebond cracked concrete. Cracks to beinjected with polyurethane resin should not be lessthan 0.005 inch in width. No upper limit on crackwidth has been established for the polyurethaneresins at the time this is being written. Polyurethane resins are available withsubstantial variation in their physical properties. Some of the polyurethanes cure into flexiblefoams. Other polyurethane systems cure tosemiflexible, high density solids that can beused to rebond concrete cracks subject tomovement. Most of the foaming polyurethaneresins require some form of water to initiate thecuring reaction and are, thus, a natural selectionfor use in repairing concrete exposed to water orin wet environments. At the time this is written,there are no standard specifications forpolyurethane resins equivalent to the StandardSpecification for Epoxy-Resin-Base BondingSystems for Concrete, ASTM Designation C-881. This current lack of standards, combinedwith the wide variations possible inpolyurethane physical properties, creates thenecessity that great care be exercised inselecting these resins for concrete repair. "Cookbook" type application of these resins willnot be successful. The Materials Engineeringand Research Laboratory (D-8180) of theDenver Technical Services Center is currentlytesting and evaluating these very useful resinsystems. They will provide advice and guidancefor field applications if requested.

Because of the high costs (generally about$200.00 per linear foot of injected crack), resininjection is not normally used to repair shallow,drying shrinkage, or pattern cracking.

The Standard Specifications for Repair ofConcrete, M-47 in appendix A contains currentmaterials and procedures specifications forepoxy and polyurethane injection resins.

(a) Preparation.—Cracks, joints, or lift lines tobe injected with resin should be cleaned toremove all the contained debris and organicmatter possible. Several techniques have beenused, with varying degrees of success, forcleaning such cracks. Once injection holes havebeen drilled, repeated cycles of alternatelyinjecting compressed air followed by water havebeen very useful in flushing and cleaning crackssubject to water leakage. The successful use ofsoaps in the flushing water has been reported bysome practitioners. Complete removal of suchmaterials once injected into cracks istroublesome and may create more problemsthan it is worth. The use of acids to flush andclean cracks is not allowed by Reclamation. Cracks subject to epoxy injection for purposesof structural rebonding should not normally beinjected with water. The epoxy resins will bondto wet concrete, but they develop higher bondstrength when bonding to dry concrete.

(b) Materials.—Epoxy resin used for crackinjection should be a 100-percent solids resinmeeting the requirements of specificationASTM C-881 for type I or IV, grade 1, class Bor C. If the purpose of injection is to restore theconcrete to its original design load bearingcapabilities, a type IV epoxy should be specifiedand used. If the purpose does not involverestoration of load bearing capabilities, a type Iepoxy is sufficient. No solvents or unreactivediluents should be permitted in the resin.

Polyurethane resin used for crack injectionshould be a two-part system composed of 100-percent polyurethane resin as one part andwater as the second part. The polyurethaneresin, when mixed with water, should becapable of forming either a closed cell flexiblefoam or a cured gel, dependent on the water toresin mixing ratio. However, the resin shouldbe such that, with appropriate water to resinmixing ratios, the resulting cured resin foam canattain at least 20-psi tensile strength with a bond


82

to concrete of at least 20 psi and a minimumelongation at tensile failure of 400 percent. Themanufacturer’s certification that his productmeets these minimum requirements should berequired before the injection resins are acceptedfor use on the job.

(c) Injection Equipment.—Resins can beinjected with several types of equipment. Smallrepair jobs employing epoxy resin can use anysystem that will successfully deposit the epoxyin the required zones. Such systems could use aprebatch arrangement in which the twocomponents of the epoxy are batched togetherprior to initiating the injection phase withequipment such as small paint pressure pots. The relatively short pot life of the epoxy makesthis technique rather critical as far as timing isconcerned.

Large epoxy injection jobs generally require asingle-stage injection technique in which thetwo epoxy components are pumpedindependently of one another from the reservoirto the mixing nozzle. At the mixing nozzle,located adjacent to the crack being repaired, thetwo epoxy components are brought together formixing and injecting. The epoxy used in thisinjection technique must have a low initialviscosity and a closely controlled set time. Several private companies have proprietaryepoxy injection systems (figure 62). Theseorganizations have developed epoxies andtechniques which allow them to makesatisfactory repairs under the most adverseconditions. One or more of these companiesshould be contacted regarding any major repairsrequiring the epoxy injection technique. Namesand addresses of these companies can beobtained from the Materials Engineering andResearch Laboratory, Code D-8180, Denver,Colorado.

Polyurethane resins have a very short pot lifeafter mixing and are always prepared andinjected with multiple component, single stageproprietary equipment similar to that used forlarge scale epoxy repairs. Reclamationspecifications do not permit single componentinjection of 100-percent pure resin. In every

instance, multiple component water-resinmixtures or resin (part A) -resin (part B)mixtures must be used. This equipment mixesthe resin system components just prior to thepoint of crack injection. The size of poly-urethane injection equipment varies from small,hand operated, pumps to full size commercialequipment capable of discharging many cubicfeet of resin per hour (figures 63 and 64). Thepumping pressure required of polyurethaneinjection equipment may exceed 3,000 psi. There are a number of manufacturers of highquality polyurethane resin injection equipment,and there is seldom any cause to attemptpolyurethane injection on a Reclamation projectwith equipment designed for, or adapted from,other operations. Such adaptation is usuallyindicative of an inexperienced contractor and ishighly discouraged.

(d) Application.—The success of resin injectionrepair projects is directly related to theexperience and knowledge of the injectioncontractor. Reclamation requires that aninjection contractor have a minimum of 3 years’ experience in performing injectionwork similar to that being contracted for andthat a minimum of five projects be included inthat experience. Reclamation may also acceptan injection contractor not having the requiredexperience provided that the work is per-formedunder the full-time, direct technical supervisionof the injection resin manufacturer, provided themanufacturer has a minimum of 5 years’experience providing resins for applicationssimilar to those specified.

(1) Application of Epoxy Resin by PressureInjection.—The objective of epoxy resininjection is to completely fill the crack ordelamination being injected and retain the resinin the filled voids until cure is complete. Thefirst step in the resin injection process is tothoroughly clean the concrete surface in thevicinity of the cracks of all loose or deterioratedconcrete and debris. The area of injection isthen inspected and the injection port locationpattern established. Several different types ofinjection patterns can be used:


83

Figure 62.—Proprietary epoxy injection equipment. Such equipment does not mixresin components until the point of injection.


84

Figure 63.—Commercial polyurethane injection pump.


85

Figure 64.—This is an air-powered pump system used for large scale polyurethaneresin injection.

C If the cracks are clearly visible andrelatively open, injection ports can beinstalled at appropriate intervals bydrilling directly into the crack surface. Care should be taken in drilling the portsto prevent drilling debris and dust fromblocking or sealing the openings. Specialvacuum drill chucks are available for thiswork. The surface of the crack betweenports is then sealed with epoxy paste andthe paste is allowed to cure. Epoxyinjection begins at the lowest elevationport and proceeds along and up the crackto the uppermost port.

C A more positive method is to drill holeson alternate sides of the crack, angled tointersect the crack plane at some depthbelow the surface. This method ensuresthat the crack will be intersected even if itstrikes or dips in unexpected directions. The top surface of the crack is then sealedwith epoxy paste, and injection isaccomplished as described above.

Low to moderate epoxy injection pressures

should be used and patience should be exercisedto permit the resin to flow and completely fillthe voids existing in the concrete. The use ofhigh injection pressures can result in flowblockage and incomplete filling and, generally,is an indication of an inexperienced contractor.

The best method of ensuring quality epoxyinjection work is to require the contractor toprepare and submit for approval his overall,detailed injection plan and then to obtain smalldiameter proof cores from the injected concrete. If more than 90 percent of the voids in the coresare filled with hardened epoxy, the injection canbe considered complete. If injection is notcomplete, the contractor should be required toreinject the concrete and obtain additional coresat no additional cost to the Government.

(2) Application of Polyurethane Resin byPressure Injection.—The basic procedure forpolyurethane injection consists of first gainingcontrol of the leaking water, followed bypressure injecting resin to seal the cracks. Inmost instances, the polyurethane injectionprocedure is almost identical to the processes


86

followed for cementitious grouting.

To gain control of the waterflow, holes aredrilled to intercept the waterflow paths as far aspossible from the concrete surface. Valveddrains known as "wall spears" (figure 65) areinstalled in the drilled holes, opened, and usedto relieve water pressure in the cracks near thesurface. The cracks are then temporarily sealedwith wood wedges, lead wool, or resin soakedjute rope to prevent excessive loss of injectionresin.

Additional resin injection holes are then drilledon alternate sides of the crack at a maximumspacing of 24 inches. These holes are angled tointercept the crack at a depth of 8 to 24 inches(as concrete thickness allows, these holes shouldextend as deeply as possible). Injection ports ofvarious design (figure 66) or additional valvedwall spears may be installed in the drilled holes,depending on the injection plan and thepresence of flowing water.

Polyurethane resin injection should occuraccording to a preplanned sequence. A systemof split spacing similar to cementitious groutingis often successful. In such a system, theprimary holes are injected first, followed bydrilling and injection of secondary holes locatedbetween the primary holes. Similarly, tertiaryholes, located between the secondary holes andprimary holes are then drilled and injected. Injection pressures should be the minimumpressures necessary to accomplish resin traveland filling. Even so, pressures of 1,500 to 2,000psi are common in this work. Closure of eachinjection hole should be accomplished byholding injection pressure for a period of 10 to15 minutes after injection flow has ceased. Thistechnique of "closure to absolute refusal"ensures that the resin attains maximum densityin the crack and becomes a permanent repair. Itis usually a mistake to stop injection as soon asthe water leakage is stopped. If such aprocedure is followed, the partially cured, lowdensity resin can be pushed out of the cracksystem by hydrostatic pressure, and repeatinjection will be required to seal the resultingleakage.

It is also common practice to intermittentlyinject resin into a port in order to accomplishsealing of large waterflows. With thistechnique, a preselected quantity of resin isslowly injected into a port, followed by a 15-minute to 2-hour waiting period beforerepeat injection. Several such cycles ofinjection may be necessary to control and seallarge waterflows. It is still necessary thatclosure to absolute refusal be accomplishedwith the final injection cycle.

Polyurethane resin injection is accomplishedwith varying water to resin ratios. In cases ofhigh waterflows, it may be desirable to injectwater to resin ratios as low as 0.5:1. Alternatively, the water and resin may beintroduced and mixed in a "residence tube" 1 to5 feet before the point of injection so thefoaming reaction may be well underway uponentering the crack network. Special downholepackers can be utilized to inject resin at pointsdeep within a structure. If resin components aremixed and injected at the surface of such deepholes, the reaction will occur within the drillhole before reaching the desired point ofinjection into the cracks. These special packers(figure 67) allow separation of the resincomponents until they reach the downhole pointof crack injection.

The necessity of using experienced injectioncontractors or technical advisors for work of thisnature cannot be overemphasized.

(3) Cleanup.—At the completion of resininjection, all injection ports, excess resin, andcrack surface sealer should be removed fromsurfaces that are visible to the public. This canbe accomplished by scraping, high pressurewater blasting, or grinding. The use of dry packor other replacement repair material necessaryto fill injection holes should be anticipated andprovided by the specifications.

35. High Molecular Weight Methacrylic SealingCompound.—Concrete sealing compounds (seealso section 38) are applied to cured, dryconcrete as a maintenance procedure to reduceor prevent penetration of water, aggressive


87

Figure 65.—An injection port with zirc fitting and a valved wall spear are shown in thisphotograph. The wall spear can be used to relieve water pressure and to inject resin.


88

Figure 66.—Several different types of injection ports are shown in this photograph.

solutions, or gaseous media and the associateddeterioration, such as freeze-thaw, carbonation,or sulfate damage. These materials replace thelinseed oil based treatment, which was generallymisunderstood and is no longer recommendedfor use on Reclamation concrete.

A variety of different membrane forming(similar to paints or coatings) and surfacepenetrating chemicals are manufactured andsold as sealing compounds for concretesurfaces. Some of these materials provide verygood protection to the concrete for discreteperiods of time. Other commercially availablesealing materials, however, may be little morethan mineral spirits and linseed oil. Suchsystems will, at best, do little harm to theconcrete. Their application may, however,prevent subsequent treatment with the sealingcompounds that have been proven effective. For this reason, only products that have proveneffective in standardized laboratory evaluationsshould be used on Reclamation concrete. TheMaterials Engineering and Research Laboratory,D-8180, maintains a current listing of concretesealing compounds that have been found

effective for Reclamation applications.

One type of sealing compound that has proveneffective in Reclamation laboratory tests andfield applications and has been designated aStandard Repair Material is known as a highmolecular weight methacrylic monomer system. This sealing compound is composed of amethacrylic monomer and appropriatepolymerization "catalysts" very similar to themonomer system used in polymer concrete(section 32). It is a water thin, amber coloredliquid that is easily spread over horizontal andvertical concrete surfaces with brooms orsqueegees. The liquid penetrates the concretesurface to a depth of about 1/16 inch but is mosteffective in penetrating and sealing cracks inthe concrete surface. This sealer will act like amembrane forming system if excess monomer isapplied or if two or more applications are made. The appearance of the concrete followingapplication will be somewhat like a varnished orwater wet surface and may be splotchy in areasof high and low absorption. Cured sealer left onthe surface of the concrete will be deterioratedby solar radiation within 1 to


89

Figure 67.—A proprietary downhole packer allows separation of the resin components untiltheyreach the downhole point of injection.


90

2 years and will disappear. The loss of thissurface material is of no consequence since theobjective of the application is to penetrate andseal cracks where the sealer is protected fromsolar radiation deterioration. The expectedservice life of properly applied methacrylicsealing compound under typical Western Stateclimatic conditions is 10 to 15 years. Reap-plication is then necessary. Figure 68 showsapplication of a high molecular weightmethacrylic sealing compound to the crest ofKortes Dam.

(a) Preparation.—Concrete to receivemethacrylic sealing compound must be dry,clean, and physically sound. The cracks andporosity of wet or damp concrete will becompletely or partially filled with water that willprevent the desired penetration of the sealingcompound. The concrete is suitably dry if nomoisture appears under a sheet of transparentpolyethylene taped to the concrete surfaceduring a minimum 2-hour exposure to fullsunlight.

Power sweeping or hand brooming followed byblowing with high pressure compressed airshould be used to remove all debris from thesurface. Very small areas of paint, asphalt,rubber, or similar type coatings can usually beignored. It should be expected, however, thatthe methacrylic monomer system will attack anddeteriorate most markings or coatingsintentionally placed on the concrete. Deteriorated or unsound concrete should beremoved following the methods described insection 8. After proper preparation, the concretemust be protected from construction traffic andwetting.

(b) Materials.—The high molecular weightmethacrylic sealing compound is usuallyobtained from the manufacturer as a three-component system:

(1) A water thin liquid methacrylicmonomer

(2) Cuemene hydroperoxide initiator (orcatalyst)

(3) Cobalt napthenate promoter

Each manufacturer will specify the properproportions for mixing these materials, andthese recommendations must be closelyfollowed. As a general rule, it can be expectedthat the initiator will be added to the monomerat about 4 to 6 percent, by weight and thepromoter at about 1 to 3 percent, by weight. The initiator and promoter must never bedirectly mixed with each other, as this willproduce an extremely violent and explosivechemical reaction. Rather, the initiator is firstthoroughly mixed with the monomer and thenthe promoter is added and mixed with themonomer-initiator mixture.

Some manufacturers supply a two-partmonomer system already containing the properproportion of promoter. With such systems, it isnecessary to add only the proper quantity ofinitiator. Once all the components are mixed,the sealing compound system will have adefinite and short pot life that cannot beextended under normal conditions.

For this reason, if the project is of sufficient sizeto require more than 5 gallons of sealingcompound, it is usually best to premeasure therequired quantity of monomer into separate 5-gallon volumes which are not mixed but areplaced at appropriate locations along theapplication path; each location consists of5 gallons of monomer, the appropriate quantityof initiator, and the separate and appropriatequantity of promoter (if not already added to themonomer by the manufacturer). Duringapplication, as one 5-gallon volume of sealingcompound is nearly used up, an additional 5gallons can then be mixed for use. Since all the5-gallon materials quantities are premeasuredand located along the application path, thissystem also helps ensure that all necessarycomponents are added and mixed for eachvolume of sealing compound. Otherwise, it issome-what common to discover that either theinitiator or the promoter has been omitted fromsealing compound already applied to the concrete, thereby creating a bothersomesituation.


91

(c) Application.—As the mixed monomersystem has a distinctly short pot life at normalambient temperatures, it is important not to mixmore material than can be easily applied prior tothe system becoming too thick— normallywithin 15 to 20 minutes. If the material is beingapplied by two workmen and the applicationpath is clear and easily attained, it would becommon to mix up to 5-gallon quantities ofmaterial unless the ambient temperatures exceed85 EF. The sealant should be appliedimmediately after mixing. Application of thesealant system to concrete in direct sunlightshould be avoided. Solar radiation greatlyshortens the working pot life of the mixedsealant. Workmen can use squeegees, industrialsize paint rollers, push brooms, brushes, orairless powered spray systems to apply thesealant system. What is desired is to flood theconcrete with a heavy uniform coverage withoutleaving puddles of excess material. Applicationrates will normally vary from 75 to 100 squarefeet per gallon, depending on surface roughnessand absorption. Vertical surfaces shouldreceive two or more brushed, sprayed, or rolledapplications. Repeat applications should bemade immediately, without waiting for thesealant to cure.

If a skid-resistant surface is required for foot orvehicle traffic, sand must be broadcast over theliquid sealant system within 15 to 20 min-utesof application. The sand gradation is containedin the appendix A specifications. The sandapplication rate should be about 1/4 to 1/2pound per square yard of surface

(d) Curing and Protection.—After application,the treated surfaces should be protected for aminimum of 24 hours. Protection should beprovided for 48 to 72 hours if ambienttemperatures are lower than 50 EF to permit thesealant to fully cure. Sealant applied during thenight will be quickly cured by solar radiation thefollowing morning. Night applications allowthe maximum penetration into cracked surfacesand should be pursued whenever practicable.

(e) Safety.—The safety provisions of section33.(e) should be followed when using high

molecular weight methacrylic sealants. Storageof initiator and promoter in the same room isprohibited. Storage of initiator underrefrigerated conditions is desirable. Everyprecaution should be taken to prevent mixing ordirect contact of initiator and promoter.

36. Polymer Surface Impregnation.—Thepolymer surface impregnation process wasdeveloped by Reclamation for the FederalHighway Administration to prevent chloridedeicing salt penetration and subsequentcorrosion of reinforcing steel in existingconcrete highway bridge decks. The processhas provided in excess of 20 years of highlysuccessful protection to many highway bridgedecks and was applied to the entire roadwaysurface over Reclamation's Grand Coulee Dam.

In this process, the concrete to be treated is firstcovered with a bed of sand and dried with heatto remove moisture from the zone to beimpregnated. A low viscosity methylmethacrylic monomer system is applied to thesandbed under a heavy polyethylene sheet andallowed to soak into the concrete surface forabout 6 hours. The polyethylene retardsevaporation of the highly volatile monomersystem, and the sand acts as a reservoir,retaining the monomer system on the concreteuntil it soaks into the surface. The polyethylenecovered sand and treated surface is thenreheated to initiate in-situ polymerization of themethyl methacrylate monomer system withinthe structure of the concrete. Concrete sotreated will be virtually impervious to waterabsorption and freeze-thaw deterioration.

Detailed materials and performancespecifications for the polymer surfaceimpregnation process are contained in section3.13 of appendix A. Users consideringapplication of this procedure should carefullyappraise the current costs and associated safetyissues. The costs of energy to properly dry andreheat areas of concrete may preclude largescale use of this very effective preventativemaintenance process.


92

Figure 68.—High molecular weight methacrylic sealing compound is being appliedtothe crest of Kortes Dam, near Casper, Wyoming.

37. Silica Fume Concrete.—Silica fumeconcrete is conventional portland cementconcrete containing admixtures of silica fume. Silica fume is a finely divided powder by-product resulting from the use of electric arcfurnaces. When mixed with portland cementconcrete, silica fume acts as a "super pozzolan." Concrete containing 5 to 15 per-cent silica fumeby mass of cement commonly can develop10,000- to 15,000-psi compressive strengths,reduced tendency to segregate, very lowpermeabilities, and enhanced freeze-thaw andabrasion-erosion resistance. Reclamation use ofsilica fume is primarily for the purpose ofenhancing or improving concrete durability withless emphasis on strength improvement.

Silica fume concrete is the repair material ofchoice for applications requiring enhancedabrasion-erosion resistance and/or reducedpermeability. Silica fume concrete requires avery thorough curing procedure, however, andshould not be used unless such a procedure canbe accomplished. Otherwise, this repairmaterial is used in accordance with theprovisions for conventional replacement

concrete.

The silica fume admixture can be obtained in atleast three forms for use in concrete:

(1) Silica fume powder

(2) Densified silica fume powder with orwithout a high range water reducingadmixture (HRWRA) and other dry admixtures

(3) Silica fume-water slurry with HRWRAand other admixtures

The dry silica fume powder is difficult to usebecause of its extremely small particle size. The fine powder drifts and spreads in any draftor air movement and can create silicaterespiratory problems to workers. The waterslurry form is easy to use, creates no dustproblems, but does involve an additional mixingstep as the slurry settles during storage andshipment and must be stirred and remixed priorto use. The water in the slurry must beaccounted during mix design. Transportationcosts of the slurry must also be considered. The


93

densified powder form is currently the mostconvenient form to ship and use. In this form,the silica fume powder is compacted anddensified and does not produce nearly thequantity of dust that occurs with the powderedform. It is a dry material and does not createadditional shipping costs. Because it has beencompacted into clumps, it should be expectedthat additional time would be required duringmixing to fully break up and disperse thedensified silica fume admixture in the concretemixture.

Because of these various forms, it is essentialthat trial mixtures be prepared and tested duringmix design to ensure development of the desiredconcrete properties.

The addition of silica fume admixture toconcrete will increase the water requirement dueto the high surface area of the very fine silicafume particles. The use of HRWRA is thusnecessary to obtain the maximum strength anddurability with silica fume concrete. Provisionsshould be made during proportioning, however,to accommodate the slump gain commonlyassociated with concrete containing HRWRA. Silica fume increases the cohesion or"stickiness" of the concrete and can result inworkability and finishing problems for thoseinexperienced in the proper finishingtechniques. It is of primary importance to placeand finish silica fume quickly, before excessivemix water evaporation and stiffening occurs. The slump gain from the HRWRA commonlyoffsets some of the "stickiness" of silica fumeconcretes. Reclamation requirements include 4-6 percent entrained air in silica fume concrete. This addition of air entraining admixture alsoimproves the workability of the concrete.

Special repair techniques are required forrestoration of damaged or eroded surfaces ofspillway or outlet works tunnel inverts andstilling basins. In addition to the usual forces ofdeterioration, such repairs often must withstandenormous dynamic and abrasive forces fromfast-flowing water and sometimes fromsuspended solids. The enhanced abrasion-erosion resistance and high strength of silicafume concrete makes it the repair material ofchoice for these types of repair. It should berecognized, however, that the cause(s) of the

original damage in such repairs must bemitigated if a permanent repair is to beaccomplished.

Whenever practicable, low slump silica fumeconcrete should be used for these types ofrepair. Slump of the concrete should not exceed2 inches for slabs that are horizontal or nearlyhorizontal and 3 inches for all other concrete.(This is 1 inch less slump than required in theM-47 specifications for conventionalapplications of silica fume concrete.) The netwater-cementitious ratio (exclusive of water ab-sorbed by the aggregates) should not exceed0.35, by weight. An air-entraining agent shouldbe used, and a high range water reducingadmixture should be used. Set-retardingadmixtures should be used only when theinterval between mixing and placing is quitelong.

(a) Preparation.—Concrete to be repaired withsilica fume concrete should be prepared inaccordance with the requirements ofsection 8.

(b) Materials.—There are currently no ASTMspecifications for the silica fume admixture. Reclamation has been approving silica fumemeeting the requirements of the StandardSpecification for Microsilica for Use inConcrete and Mortar, AASHTO Designation: M307-90.

All other materials, including the requirementfor 4- to 6-percent entrained air, should be inaccordance with the provisions of section 29.

(c) Application.—Silica fume concrete must bemixed, transported, and placed in accordancewith the highest quality procedures forconventional concrete technology and with theprovisions of section 29.

The following silica fume concrete mix designis included as a reference or starting point only. Proper proportioning of silica fume concreterequires trial mixes:


94

Material

Portland cementCoarse aggregate (3/4-in. MSA)SandWaterSilica fume slurry1 = 13.3 percent by mass of cement

679.3 lb/yd3

1,910.9 lb/yd3

1,036.2 lb/yd3

169.0 lb/yd3

200.6 lb/yd3

TotalHRWRA

3,996.0 lb/yd3

300 cc

w/c ratio = Water + 0.51(slurry) = 239.2 = 0.35Cement + 0.45(slurry) = 769.5

1 Silica fume slurry contains 51 percent water, 45 percent cementitious silica fume, and 4 percentadmixtures, all by mass. The admixtures consist of HRWRAand air entraining admixture. In this instance, additionalHRWRA was required to produce a workable concrete.

Silica fume concrete is placed and finishedusing conventional equipment and procedures. As previously discussed, placement should bedone quickly to allow finishing before stiffeningoccurs. Consolidation and compaction shouldbe accomplished with internal vibrators. Vibrating screeds can be used for largerplacements and, usually, a single pass ofmultirow screeds will provide an adequatesurface finish. Small repair areas can be handscreeded (figure 69). Bull floats can be usedafter screeding, but floating must be doneimmediately after screed passage (figure 70). Hand troweling silica fume concrete is usuallynot too effective, except for small repairs,because it takes too long. There is very littlebleed water development after placing silicafume concrete. This can result in plastic anddrying shrinkage cracking under conditions ofelevated temperatures, low humidity, and highwind conditions which cause rapid waterevaporation from the concrete surface (seesection (d) below). The use of a long chaincetyl alcohol evaporation retarding finishing aidis highly recommended under such conditions.

(d) Curing.—Silica fume concrete must beproperly cured if a successful repair is to result. Fresh silica fume concrete has very low or nobleed water development. This is due to theaffinity silica fume has for water and to the lowwater-cement ratio of the mix. If the rate ofevaporative water loss from the surface of

freshly placed silica fume concrete exceeds therate of bleed water development, plasticshrinkage cracking of the surface will result. Evaporative water loss must be prevented bysuch measures as immediate application ofcuring compound, covering the fresh concretewith plastic membrane, water fogging orflooding, use of an evaporation retardingfinishing admixture, and by immediate curing. The common practice (with conventionalconcrete) of allowing the development andevaporation of bleed water from the surfaceprior to beginning curing will always result incracking of silica fume concrete. It is best tobegin the curing of silica fume concreteimmediately after finishing. Very successfulcuring of stilling basin repairs has resulted fromflooding the repair area with water immediatelyafter the silica fume concrete has attained initialset. Even so, water evaporation from theconcrete surface must be prevented prior toflooding. The spillway repairs shown in figures69 and 70 were cured by applying curingcompound and covering with polyethyleneimmediately after floating, even while placingoperations were continuing (figure 71). Watertrickler hoses were placed under thepolyethylene as soon as the concrete attainedinitial set, and water was applied continuouslyfor 14 days. This thin, 4- to 6-inch deep, repair has experienced virtually noshrinkage cracking.

(e) SafetyThe same safety provisions should befollowed as with the use of any portland cementproduct, except that additional precautions must betaken to prevent inhalation of silica fume dust. Thehigh silica content of silica fume dust can lead todevelopment of silicosis if proper respirators arenot used by workmen participating in or downwindof mixing operations.

38. Alkyl-Alkoxy Siloxane SealingCompoundThis sealing compound is effective inreducing water penetration into treated concrete,provided that the sealing compound contains inexcess of 15-percent siloxane solids. Thesesolids are suspended in a carrier such as alcoholor mineral spirits that evaporates from theconcrete following application. Use of this typeof sealing compound does not cause a


95

Figure 70.—Using a bull float on a silica fume repair. Finishing must be doneimmediately after screeding.

Figure 69.—This workman is hand screeding a small silica fume concrete repair.


96

Figure 71.—Curing compound and polyethylene sheeting should be applied to curesilica fumeconcrete as soon as finishing is completed if drying shrinkage cracking isto be prevented.

change in the appearance of the treatedconcrete, except that the darkening normallyassociated with water wetting of concrete doesnot occur. It is common to see water bead ontreated concrete surfaces. Siloxane sealingcompounds will not provide protection toconcrete that is completely inundated in waterexcept for short periods. They should not beused under conditions that involve prolongedinundation such as occurs with stilling basins,canal floors, or spillway floors unless there aresignificantly long dry periods betweeninundations and it is acceptable to reapply thesealing compound following inundation. Siloxane sealing compound is best used toprotect concrete from rain, snowmelt, and watersplash zones.

These materials have a relatively limited servicelife, and reapplication should be scheduledabout every 5 to 7 years for optimum protection. Application of these materials, however,proceeds very quickly on horizontal and verticalconcrete surfaces. Two workmen can beexpected to treat 10,000 to 15,000 square feet of

horizontal surface in a day. Cost of siloxanesealing compound and application averageabout $0.50 to $0.70 per square foot.

(a) Preparation.—Concrete surfaces to betreated with siloxane sealing compound shouldbe dry, clean, and sound. All deterioratedconcrete should be removed (section 8), and allneeded repairs should be accomplished prior toapplication. As a general rule, power sweepingand, in some instances, high pressure (less than8,000 psi) water washing of the surfaces will besuf-ficient. The concrete should be allowed todry for 24 to 48 hours following wetting. Cracks in the concrete should be cleaned andblown out with compressed air to remove anydebris. Once preparation (including drying ifneeded) is completed, the sealing compoundshould be applied within 24 hours.

(b) Materials.—Siloxane sealing compoundshould be a one-part, ready to apply, oligo-meric alkyl-alkoxy siloxane containing no lessthan 20 percent active solids, by mass, in a clearorganic carrier. Siloxane sealing compounds


97

Figure 72.—A paint roller application of siloxane sealing compound to thedownstream face of Nambe Falls Dam, near Santa Fe, New Mexico.

containing less than 20 percent active solids donot provide sufficient protection to the concreteand are not allowed by section 3.15.d of the M-47 specifications in appendix A. The materialshould be supplied in 5-gallon pails or 55-gallondrums. No additional mixing or blendingshould be necessary prior to application. Noadditional solvents or diluents should be addedto the supplied sealing compound.

(c) Application.—The sealing compound shouldbe applied to the concrete using squeegees, pushbrooms, paint rollers (figure 72) or low pressureairless spray equipment. Adjacent glass, metal,and painted surfaces must be protected from thesealing compound. Overspray protection mustbe provided if spray application equipment isutilized. Fine spray mists can travel extensivelyand damage downwind structures, equipment,and automobiles.

The application rate should be 1 gallon per80 to 120 square feet of concrete surface. Horizontal and vertical surfaces should receivetwo wet to wet coatings, 5 or so minutes apart,flooding the surface each time. Excess sealant

should be broomed out until it is absorbed bythe concrete. Low density areas of the concretesurface need the most protection, and theseareas are the most absorptive.

(d) Curing.—Siloxane treated concrete must beprotected from foot and vehicular traffic andwater wetting for 24 hours followingapplication. Should the concrete experiencerain or heavy water splashing during this period,the drying step of preparation should berepeated and reapplication made.

(e) Safety.—Siloxane sealing compounds areformulated with organic solvents such asalcohol or mineral spirits. Materials SafetyData Sheets should be consulted concerningflammability and toxicity. Applicators shouldwear protective coveralls, rubber boots, eyeprotection, and approved respirators.

98

Chapter V

Nonstandard Methods of Repair

39. Use of Nonstandard Repair Methods.—The standard concrete repair methods/ materialsdiscussed in chapter IV will meet nearly allconcrete repair needs. There will be occasions,however, resulting from unusual causes ofdamage and exposure conditions or specialrepair needs, when the standard repair methodsmay not meet the performance needs. In theseinfrequent instances, non-standard repairmethods may be required.

Repair materials are considered to be non-standard if they have not been thoroughly testedand evaluated for Reclamation applications. The use of such materials involves a certainelement of risk because the performanceproperties of these materials are unknown or notfully defined. The application of nonstandardmaterials can be justified only when it has beendetermined that no standard repair material willserve, and if all parties associated with orresponsible for accomplishing the repairs are made to understand the risks and agree to accept the uncertainties and possibleconsequences.

An example of such a situation would be theneed to repair concrete damage on the crest of adam that is less than 1-1/2 inches deep. Thereis no standard repair material suitable for suchshallow repairs when exposed to sunlighttemperature variation conditions. (Theseconditions eliminate the use of epoxy mortars.) The current standard repair material for depthsbetween 1-1/2 inches and 6 inches is epoxy-bonded replacement concrete. If thedeterioration is not at least 1-1/2 inches deep,sufficient concrete must be removed toaccomplish a 1-1/2- inch depth. If, for somereason, it was undesirable or impossible toremove the required depth of concrete, it mightbe appropriate to select one of the proprietarythin repair products. These materials have been

only partially evaluated (Smoak and Husbands,1996) and the long- term field performance hasnot yet been fully determined. In this example,the people responsible for the dam must becontacted, and the risks of using an unprovenrepair material must be made known to them. These responsible personnel, with thisknowledge, can then determine if the benefits ofperforming the shallower repairs wouldoutweigh the uncertainties associated withunproven performance.

(a) Preparation.—Concrete preparation forrepair with nonstandard materials should be inaccordance with section 8 unless requiredotherwise by the materials manufacturer. Therecommendations of the manufacturer should beclosely followed.

(b) Materials.—Nonstandard repair materialswill be proprietary or commercial products inmost instances. Manufacturer's technicalrepresentatives should be contacted and madefully aware of the nature of the problem and thecauses for selecting nonstandard repairmaterials. They must be informed of anysecondary considerations, such as the need toaccomplish repairs on an emergency basis or theinability of taking the structure to be repairedout of service except at certain times. Copies ofmaterials warranties should be obtained ifavailable. Technical representatives should bequestioned closely about the conditions underwhich their materials would not be suitable foruse or when the materials warranties would notapply. The manufacturer should be able tosupply case studies or project histories of use oftheir materials to repair similar damage.

(c) Application.—Application of nonstandardrepair materials must be made in exactconformance to the manufacturer'srecommendations. Failure to apply the


99

materials properly will void any warranties andis a commonly cited reason for proprietarymaterial failure. Construction inspectionreports should closely note any contractorvariance from the manufacturer's recommendedapplication procedures.

(d) Curing.—Curing of nonstandard repairmaterials must be performed exactly asrecommended by the materials manufacturer.

(e) Safety.—Nonstandard repair materials couldcontain compounds not commonly encounteredduring repair construction. Copies of theMaterials Safety Data Sheets must accompanythe shipment of materials to the jobsite. Theyshould be consulted and appropriate safetyprovisions developed.

Appendix A

Standard Specifications for the Repair of ConcreteM-47, 08-96

M-47

(M0470000.896)

STANDARD SPECIFICATIONS

FOR REPAIR OF CONCRETE

August 1996

United StatesDepartment of the Interior

Bureau of ReclamationTechnical Service Center Denver Federal Center

Denver, Colorado 80225-0007

M-47 (M0470000.896)Page 1 of 738-1-96

Contents

Page

How to Use This Manual . . . . . . . . . . . . . . . . . . . . . . . 1

1. General requirements . . . . . . . . . . . . . . . . . . . . 5

1.1 General . . . . . . . . . . . . . . . . . . . . . . . 51.2 Designs . . . . . . . . . . . . . . . . . . . . . . . 51.3 Submittals . . . . . . . . . . . . . . . . . . . . . . 51.4 Quality assurance . . . . . . . . . . . . . . . . . . 51.5 Materials and workmanship . . . . . . . . . . . . . . 61.6 Safety . . . . . . . . . . . . . . . . . . . . . . . 71.7 Repair procedures . . . . . . . . . . . . . . . . . . 7

2. Concrete preparation for repair . . . . . . . . . . . . . . 8

2.1 Removal and cleaning . . . . . . . . . . . . . . . . 82.2 Saw cut edges . . . . . . . . . . . . . . . . . . . . 82.3 Reinforcing steel . . . . . . . . . . . . . . . . . . 82.4 Maintenance of prepared surfaces . . . . . . . . . . 8

3. Specifications for repairing concrete . . . . . . . . . . . 8

3.1 Surface grinding . . . . . . . . . . . . . . . . . . 83.2 Portland cement mortar . . . . . . . . . . . . . . . 93.3 Dry pack and Epoxy Bonded Dry Pack . . . . . . . . . 103.4 Preplaced aggregate concrete . . . . . . . . . . . . 113.5 Shotcrete . . . . . . . . . . . . . . . . . . . . . . 203.6 Concrete replacement . . . . . . . . . . . . . . . . 283.7 Epoxy bonded epoxy mortar . . . . . . . . . . . . . . 303.8 Epoxy bonded concrete . . . . . . . . . . . . . . . . 363.9 Polymer concrete systems . . . . . . . . . . . . . . . 393.10 Thin polymer concrete overlay . . . . . . . . . . . . 453.11 Resin injection . . . . . . . . . . . . . . . . . . . 483.12 High molecular weight methacrylic sealing compound . . 533.133 Surface impregnation . . . . . . . . . . . . . . . . 58

3.14 Silica fume concrete . . . . . . . . . . . . . . . . . . 64 3.15 Alkyl-alkoxy siloxane sealing compound . . . . . . . . . 68

M-47 (M0470000.896)Page 2 of 738-1-96

2

HOW TO USE THIS MANUAL

This manual is divided into 3 sections. The general requirements containedin section 1 and the concrete preparation requirements contained in section2 always apply to each and every Reclamation concrete repair project. Section 3 consists of a number of paragraphs containing the specialrequirements of the various repair materials and techniques. Once a repairmaterial/technique has been properly selected from section 3 (see "Step 4.Choose An Appropriate System" below) it should be sufficient in preparing ajob specific specification to simply require that the repairs be performedin accordance with the provisions of section 1, section 2, and section 3.Xof this manual. Assistance in using this manual or with any other phase of concrete repairof Reclamation structures can be obtained by contacting:

Glenn Smoak or Kurt von Fay Materials Engineering and Research Laboratory Code D-8180 Technical Service Center P.O. Box 25007 Denver, Co 80225 phone 303-236-3730.

The standard concrete repair materials and techniques described in thismanual have been developed and evaluated by the Bureau of Reclamation overa period of some 90 years. Unfortunately, during this time many repairfailures have occurred on Reclamation concrete structures even though verydurable repair materials were specified and used. In evaluating the causesof these failures it has been learned that it is essential to consistentlyuse a systematic approach to repairing concrete. Many such such repairsystems exist and this manual will not attempt to discuss or evaluate whichof these systems is best for any set of field conditions. Rather, thefollowing repair system has been used by Reclamation over a long period oftime and has been found to result in successful concrete repairs. Thissystem, known as "The Seven Steps of Concrete Repair", is suitable forrepairing both construction defects in new concrete as well as old concretedamaged by long exposure to field conditions. In using this system it isnecessary to take the steps in numerical order. Quite often the firstquestions asked when damaged concrete is detected is "What should be usedto repair this?" or "How much will the repair cost?". These are not wrongquestions. Rather they are asked at the wrong time. With a systematicapproach these questions are asked only when sufficient information isavailable to provide correct answers.

The Seven Steps of Concrete Repair

1. Determine the cause of damage

2. Evaluate the extent of damage

3. Determine the need to repair

4. Choose an appropriate repair system

5. Prepare the old concrete

6. Apply the repair system

M-47 (M0470000.896)Page 3 of 738-1-96

7. Cure the repair properly

Step 1. Determine the cause of damage - It is essential to correctlydetermine the causes(s) of the damage to the concrete. If this is notdone, or if the determination is incorrect, the cause of damage will mostlikely attack and deteriorate the repair. The money spent for suchrepairs is, thus, totally lost and larger replacement repairs becomenecessary at much higher cost.

Step 2. Evaluate the extent of damage - The objective of this step is todetermine how much of the structure is damaged and how extensive thedamage is.

Step 3. Determine the need to repair - Not all damage to concreterequires repair. Repairs should be undertaken only if they will resultin longer or more economical service life, a safer structure, ornecessary cosmetic improvements in the structure. This step alsoincludes determination of when the structure can be taken out of servicefor repairs, an estimate of how long the repairs will take, and how tobudget the costs of the repairs.

These first 3 steps are the major components of a condition survey. Onlyafter they have properly been performed should one proceed with selectingand installing the repair materials.

Step 4. Choose an appropriate repair system - Upon completion of thefirst 3 steps, an appropriate repair system can be selected that takesinto consideration the many factors essential to a successful repair. Ina majority of the repair situations, the standard materials and methodsin this specification will fully meet all repair needs. It should berecognized, however, that service conditions or special repair situationswill occur where these "standard materials" will not meet the specialrequirements and it will be necessary to resort to "non-standard" repairmaterials or methods. Such materials are continually being tested andevaluated by Reclamation laboratory and field offices. They includematerials that may have performed quite well in laboratory tests but havenot yet been applied in the field, materials not yet having long orsufficient field service to determine service life expectancy, or newlydeveloped commercial materials not yet tested or evaluated byReclamation. It is appropriate to use such repair materials andtechniques only when it has been determined that none of the standardrepair materials will properly serve, and when it is fully understood andagreed by all involved parties that the risks associated with the use ofunproven materials are justified by the expected benefits of repairsuccess and are acceptable.

Step 5. Prepare the old concrete - The most common cause of repairfailure is improper or inadequate preparation of the old concrete priorto application of the repair material. Even the best of repair materialswill give poor service life if bonded to weakened or deteriorated oldconcrete. The provisions of section 2 of this manual provide only theminimum preparation requirements. It should be noted that each of thestandard repair materials has special preparation requirements and thatthese requirements are listed under paragraphs f of section 3. That is,for example, the special preparation requirements for replacementconcrete will be listed under paragraphs 3.6.f while those of epoxybonded concrete will be listed under paragraphs 3.8.f.

Step 6. Apply the repair system - Each standard and non-standard repairmaterial has application procedures specific for that material. For

M-47 (M0470000.896)Page 4 of 738-1-96

4

example, the procedures used with replacement concrete are vastlydifferent from those necessary for polymer concrete or epoxy bondedconcrete. It is essential that proper application techniques as listedin the section 3 paragraphs g for each material be followed exactly.

Step 7. Cure the repair properly - The second most common cause ofrepair failures is improper or inadequate curing. Each repair materialhas specific curing requirements. As an example, replacement concretebenefits from long periods of water curing while latex modified concrete,currently a non-standard material, requires 24 hours water curingfollowed by drying to allow formation of the latex film. Polymerconcrete has essentially no curing requirements while those of silicafume concrete are are exceedingly exact. Failure to achieve proper curefor the proper duration, as listed in section 3 paragraphs f, will resultin loss of the repair at the final step of the process.

SECTION 1 - GENERAL REQUIREMENTS

1.1 GENERAL

Concrete that is damaged from any cause; structural concrete that hascracked; concrete that is honeycombed, fractured, or otherwise defective;and concrete that, because of excessive surface depressions, must beexcavated and built up to bring the surfaces to the prescribed lines, shallbe repaired or replaced in accordance with these specifications andcontract requirements.

The method of repair or replacement (procedure) shall be as determined anddirected by the Contracting Officer.

Contract, as used herein, shall mean the contract which, by reference,these specifications are included in and made a part. Contracting Officer,as used herein, shall mean the person executing the contract on behalf ofthe Government, and shall include duly authorized representatives. Contractor, as used herein, shall mean the party entering into the contractwith the Government, and shall include subcontractors, suppliers,manufacturers, and agents at all tiers.

M-47 (M0470000.896)Page 5 of 738-1-96

1.2 DESIGNS

Concrete mixture proportions, compressive strengths, and other designrequirements shall be as specified in these specifications. Designs by theContractor shall be subject to the approval of the Contracting Officer.

1.3 SUBMITTALS

Submittals shall be in accordance with these specifications and thecontract requirements entitled "Submittal Requirements." The Contractorshall submit MSDS (Material Safety Data Sheets), approval drawings anddata, repair plans, certifications, material samples, test data andsamples, and other submittals as required in these specifications. TheContractor shall be responsible for the accuracy of all submittals.

Unless specified otherwise submittals shall include the original and 2copies.

1.4 QUALITY ASSURANCE

Quality assurance shall be in accordance with the requirements of thecontract entitled "Quality Assurance," and with the requirements of thesespecifications.

All concrete shall be repaired as necessary to produce surfaces conformingto the specified tolerances and finish requirements of the contract inwhich these specifications are incorporated by reference and as outlined insection 3.

If, in the opinion of the Contracting Officer, the results of concreterepair indicate that proper quality control procedures are not beingconsistently utilized, further repair work may be suspended in whole or inpart at the discretion of the Contracting Officer. Such suspension will beeffective until the Contractor demonstrates substantial improvement inquality control procedures and repair results.

a. Contractor's quality control. - In accordance with the clause in thecontract entitled "Inspection of Construction," the Contractor shall beresponsible for providing quality control measures to ensure complianceof the repair with these specifications. The Contractor shall implementnecessary and appropriate quality control procedures to ensure that allconcrete repairs conform to the requirements of these specifications.

b. Government inspection and tests. - Government inspection and testswill be in accordance with the clause in the contract entitled"Inspection of Construction," and with these specifications.

Not less than 24 hours in advance of any concrete repair, the Contractorshall inform the Contracting Officer when the concrete repairs will beperformed and, unless inspection is specifically waived, the repairsshall be performed only in the presence of an authorized representativeof the Contracting Officer.

c. Testing. - Except as specified in paragraphs 3.5 and 3.12 of thespecifications the Contractor shall perform all tests. The Contractorshall provide all materials, equipment, and labor necessary forperforming the tests at no additional cost to the Government.

d. Approval. - Approval of the repairs will be based on the inspectionand testing requirements of these specifications.

M-47 (M0470000.896)Page 6 of 738-1-96

6

e. Rejection. - Repairs that fail to meet the requirements of thesespecifications will be rejected.

1.5 MATERIALS AND WORKMANSHIP

a. Materials. - The Contractor shall furnish all materials for repair ormaintenance of concrete and shall furnish all materials for forming,curing, and protection of the repairs, as required. All materials shallmeet materials specifications as specified in section 3, and allequipment used and methods of operation for the repair or maintenance ofconcrete shall be subject to approval of the Contracting Officer.

The references to materials in the specifications, wherein manufacturer'sproducts or brands are specified by "brand name or equal" purchasedescriptions, are made as standards of comparison only as to type,design, character, or quality of the article required, and do notrestrict the Contractor to the manufacturer's products or to the specificbrands named. It shall be the responsibility of the Contractor to proveequality of materials and products to those referenced and to provide alldescriptive information, test results, and other evidence as may benecessary to prove the equality of materials or products which theContractor offers as being equal to those referenced.

b. Workmanship. - Concrete shall be repaired by skilled workmen asoutlined in section 3.

1.6 SAFETY

All work shall be performed in accordance with the applicable safety andhealth standards, the requirements of Reclamation's "Health and SafetyStandards," the contract, and these specifications. Certain additionalsafety precautions shall be employed to prevent skin and eye contact withchemicals, resins, or monomeric materials. Protective glasses andclothing, including rubber or plastic gloves shall be worn by all personshandling monomeric materials. All exposed skin areas shall be protectedwith a protective barrier cream formulated for that purpose. Barrier creamfor skin protection shall be specified for the materials used and approvedby a physician. Adequate ventilation shall be provided and maintained atall times during use of monomeric materials and solvents. Fans used forventilating shall be explosion proof. If necessary, respirators thatfilter organic fumes and mists shall be worn. All contaminated materialssuch as wipes, empty containers, and waste material shall be continuallydeposited in containers that are protected from spillage. Spillage shallbe immediately and thoroughly cleaned up and disposed of in accordance withapplicable regulations.

Federal Standard No. 313, as amended, for the preparation and submission ofmaterial safety data sheets is hereby incorporated and made a part of thesespecifications.

In accordance with the clause in the contract entitled "Hazardous MaterialIdentification and Material Safety Data," the Contractor shall submit acompleted MSDS (Material Safety Data Sheet), Department of Labor Form OSHA-174, or GSA-approved Alternate Form A for each hazardous material asrequired by Federal Standard No. 313, as amended. The information in thisMSDS shall be followed to assure safe use, handling, storage, and anenvironmentally acceptable disposal of the commodity used on the job site.

M-47 (M0470000.896)Page 7 of 738-1-96

The Contractor shall submit to the Contracting Officer, not less than 30days prior to job site delivery of each hazardous material, completed MSDSand identification and certification for the material.

1.7 REPAIR PROCEDURES

All repair or maintenance procedures shall be performed in accordance withthe applicable specifications of section 3, including surface preparation,forming, finishing, and curing.

SECTION 2 - CONCRETE PREPARATION FOR REPAIR

Concrete to be repaired shall be prepared in accordance with therequirements of this paragraph and with the special requirements of section3.

2.1 REMOVAL AND CLEANING

All damaged, deteriorated, loosened, or unbonded portions of existingconcrete shall first be removed by water blasting, bush hammering, jackhammering, or any other approved method, with approved equipment, afterwhich the surfaces of existing concrete shall be prepared by containedshotblasting, wet sandblasting, or water blasting to remove anymicrofractured surfaces resulting from the initial removal process. Thesurfaces shall then be cleaned and allowed to dry thoroughly, unless thespecific repair technique requires application of materials to a saturatedsurface. Concrete removal processes involving the use of jack hammers inexcess of 30 pounds, dry sandblasting, or scrabblers shall not be usedwithout approval by the Contracting Officer. The use of acids for cleaningor preparing concrete surfaces for repair will not be permitted.

2.2 SAW CUT EDGES

The perimeters of repairs to concrete that involve concrete removal andsubsequent materials replacement shall be saw cut perpendicular to therepair surface to a minimum depth of 1 inch. Featheredge repairs toconcrete shall not be used.

2.3 REINFORCING STEEL

All loose scale, rust, corrosion by products, or concrete shall be removedfrom exposed reinforcing steel. Reinforcing steel exposed for more thanone-third of its perimeter circumference shall be completely exposed toprovide 1-inch minimum clearance between the steel and the concrete. Damaged or deteriorated reinforcing steel shall be removed and replaced asdirected by the Contracting Officer.

2.4 MAINTENANCE OF PREPARED SURFACES

After the concrete has been prepared and cleaned, it shall be kept in aclean, dry condition until the repair has been completed. Anycontamination, including oil, solvent, dirt accumulation, or foreignmaterial shall be removed by additional wet sandblasting and air-water jetcleanup followed by drying.

SECTION 3 - SPECIFICATIONS FOR REPAIRING CONCRETE

3.1 SURFACE GRINDING

M-47 (M0470000.896)Page 8 of 738-1-96

8

Where bulges, offsets, and other irregularities exceed the specifiedtolerances, the protrusions shall be repaired so that the surfaces arewithin the specified limits. Surface grinding techniques may be used forthis purpose subject to the following limitations:

a. Grinding of surfaces subject to cavitation erosion (hydraulicsurfaces subject to flow velocities exceeding 40 feet per second) shallbe limited in depth so that no aggregate particles are exposed more than1/16 inch in cross section at the finished surface.

b. Grinding of surfaces exposed to public view shall be limited in depthso that no aggregate particles are exposed more than 1/4 inch in crosssection at the finished surface.

c. Grinding of all other surfaces shall be as directed by theContracting Officer. In no event shall surface grinding result inexposure of more than one-half the diameter of the maximum-sizeaggregate.

d. Where surface grinding has caused or will cause exposure of aggregateparticles greater than the limits of subparagraph 3.1.a. or b., theconcrete shall be repaired by excavating and replacing the concrete inaccordance with paragraph 3.6 or 3.8. as directed by the ContractingOfficer.

3.2 PORTLAND CEMENT MORTAR

a. General. - Repairs with portland cement mortar shall be made only ifspecifically approved by the Contracting Officer. Approval for hand-applied cement mortar repairs will be given only for very small repairareas not associated with critical performance of the structure. Whenapproved, portland cement mortar may be used for repairing defects onexposed, new concrete surfaces if the defects are small and are too widefor dry pack and too shallow for concrete replacement and only if therepairs can be completed within 24 hours of removing the forms. Portlandcement mortar shall not be used for repairs to old or existing concreteor for repairs that extend to or below the first layer of reinforcingsteel.

b. Submittals. - Before beginning any repair work, the Contractor shallsubmit a detailed list of the equipment, procedures, and materials theContractor proposes to use for cement mortar repair to the ContractingOfficer for approval.

c. Quality assurance. - Quality assurance shall be in accordance withparagraph 1.4.

d. Materials. - Portland cement mortar shall consist of type I or typeII portland cement, clean water, and clean, well-graded sand passing a1.18-mm (No. 16) sieve. All mortar materials, including curing compoundshall meet the requirements of subparagraph 3.6.d.

e. Safety. - All work shall be performed in accordance with therequirements of paragraph 1.6.

f. Concrete preparation. - After damaged or defective concrete has beenremoved as specified in section 2, the surface on which mortar is to beplaced shall be prepared by being thoroughly cleaned of all microfractured, loose, or deteriorated materials and surface-dried.

M-47 (M0470000.896)Page 9 of 738-1-96

g. Application and Mixture Proportioning. - Portland cement mortar shallbe composed of portland cement, sand, and water, all well mixed andbrought to proper consistency. Mortar mixtures and applicationtechniques shall be in accordance with the requirements for mortarreplacement method as described in Reclamation's "Concrete Manual",Eighth Edition, revised, chapter VII. Cement mortar shall not be applieduntil approval of all submittals has been received from the ContractingOfficer.

h. Curing. - All cement mortar repairs shall be water cured for 7 daysfollowing application. At no time during this initial curing periodshall the mortar be allowed to dry. If drying occurs, the repair shallbe removed and replaced. If the repair is removed and the originalconcrete is older than the maximum specified in subparagraph 3.2.a.,another repair method shall be used in accordance with thesespecifications. Following the 7-day curing period and while the repairis still saturated, the surface of the repair shall receive two coats ofwax-base (type I) or water-emulsified resin base (type II) curingcompound meeting the requirements of subparagraph 3.6.d.

3.3 DRY PACK AND EPOXY BONDED DRY PACK

a. General. - The dry pack concrete repair technique shall be limited toareas that are small in width and relatively deep, such as core holes,holes left by the removal of form ties, cone-bolt and she-bolt holes, andnarrow slots cut for repair of cracks. Epoxy bonded dry pack shall beused for critical repairs or for repairs expected to be exposed to severeservice conditions. Dry pack shall not be used for shallow depressionswhere lateral restraint cannot be obtained, nor for filling behind steelreinforcement.

b. Submittals. - Before beginning any repair work, the Contractor shallsubmit to the Contracting Officer for approval, data for the mortarmaterials and as provided by paragraph 3.8.b.(2).


d. Materials. - Dry pack mortar shall consist of type I or II portlandcement, clean sand that will pass a 1.18-mm (No. 16) sieve, and cleanwater. All dry pack materials, including curing compound, shall meet therequirements of subparagraph 3.6.d. Epoxy bonding resin shall meet therequirements of paragraph 3.8.d.(2).


f. Concrete preparation. - Holes for dry pack shall have a minimum depthof 1 inch and shall be square at the surface edge. A careful inspectionshall be made to ensure that the hole is thoroughly clean and is in soundconcrete. The interior surfaces of the hole shall be presoaked prior toapplication of the dry pack. If epoxy bonded dry pack is to be usedpresoaking the repair area prior to application of the dry pack shall notbe performed.

g. Application. - A mortar bond coat or epoxy resin bond coat shall beapplied to the concrete hole surface prior to placing dry pack. Themortar bond coat shall consist of 1 part portland cement to 1 part sandmixed with water to give a fluid paste consistency. The mortar bond coatshall be thoroughly brushed onto the hole surfaces. The epoxy resin bond

M-47 (M0470000.896)Page 10 of 738-1-96

10

coat shall consist of materials and be applied in accordance with theprovisions of paragraph 3.8.g.(3). Dry pack mortar shall consist of 1part portland cement to 2.5 parts sand (by weight) and shall be mixedwith just enough water so that the mortar will stick together when moldedby hand and not exude water when squeezed.

The dry-pack mortar shall be immediately packed into place in 3/8-inchcompacted layers before the bond coat has dried or cured.

Each layer shall be compacted over the entire surface by tamping with ahardwood dowel and hammer. Hardwood dowels are used in preference tometal bars because the bars tend to polish the surface of each layer. The final layer shall be finished immediately after compaction by layingthe flat side of a hardwood board against the fill and striking the boardfirmly with a hammer.

h. Curing. - Proper curing is essential for a successful dry-packrepair. The surface of the repair area shall be protected from dryingand shall be kept continuously moist for 7 days. The surface of therepair shall be protected from surface drying by using burlap kept wet,wet sand, or plastic sheeting over a water soaker hose, or other methodsapproved by the Contracting Officer. After 7 days and while the surfaceis still damp, two coats of curing compound shall be applied to preventmoisture loss. The dry-pack repair area shall not be exposed to freezingtemperatures for 3 days after application of the curing compound.

3.4 PREPLACED AGGREGATE CONCRETE

a. General. -

(1) Preplaced aggregate concrete (PAC) is concrete that has been madeby forcing a grout into the voids of a mass of clean, graded, coarseaggregate. As a repair method, PAC is used where placing conventionalconcrete is extremely difficult, such as in underwater repairs,concrete and masonry repairs, or where shrinkage of concrete must bekept to a minimum. In underwater repairs, injection of grout at thebottom of the PAC displaces water, leaving a homogeneous mass ofconcrete with a minimum of paste washout.

For the purpose of this repair method, grout is defined as a mixtureof water, cementitious materials, sand, and admixtures.

(2) Reference standards and specifications for PAC. - Referencestandards and specifications for materials, testing, and proportioningPAC shall be the standards listed below. Standards and specificationsfor testing concrete and concrete materials shall be in accordancewith applicable ASTM and ACI standards.

(a) ASTM C 937 - Standard Specification for Grout Fluidifier forPreplaced-Aggregate Concrete.

(b) ASTM C 938 - Standard Practice for Proportioning GroutMixtures for Preplaced-Aggregate Concrete.

(c) ASTM C 939 - Standard Test Method for Flow of Grout forPreplaced-Aggregate Concrete (Flow Cone Method).

(d) ASTM C 940 - Standard Test Method for Expansion and Bleedingof Freshly Mixed Grouts for Preplaced-Aggregate Concrete in theLaboratory.

M-47 (M0470000.896)Page 11 of 738-1-96

(e) ASTM C 941 - Standard Test Method for Water Retentivity ofGrout Mixtures for Preplaced-Aggregate Concrete in the Laboratory.

(f) ASTM C 942 - Standard Test Method for Compressive Strength ofGrouts for Preplaced-Aggregate Concrete in the Laboratory.

(g) ASTM C 943 - Standard Practice for Making Test Cylinders andPrisms for Determining Strength and Density of Preplaced-AggregateConcrete in the Laboratory.

(h) ASTM C 953 - Standard Test Method for Time of Setting ofGrouts for Preplaced-Aggregate Concrete in the Laboratory.

(i) American Concrete Institute Standard (ACI-304), RecommendedPractice for Measuring, Mixing, Transporting, and Placing Concrete.

b. Submittals. -

(1) At least 60 days prior to beginning repair work, the Contractorshall submit for approval a repair plan for PAC construction. Therepair plan shall include detailed drawings of formwork construction,the grout injection system including sequence of injecting grout intoinsert pipes, location and spacing of injection tubes, sounding wells,and pipes; a description of all equipment including pumps, sizes anddiameters of pipes, hoses, and connections; the planned operatingprocedures and pumping rates for grout; methods of placing coarseaggregate; methods of consolidating aggregates and PAC duringgrouting; and communication facilities between the grout mixing andpumping plant and PAC placement.

The proportions of grout mixtures and fresh properties of grout shallbe submitted with the repair plan. Included with the groutproportions, shall be the voids content and compacted density ofaggregates before injection of grout, the density of hardened PAC, andthe compressive strengths of PAC at 7 and 28 days' age.

(2) The Contractor shall submit for approval to the ContractingOfficer's representative a proposed specific operating procedureincluding a hazard analysis for all preplaced aggregate concreting andgrout injecting operations. The specific operating procedure shallinclude such things as engineering controls, protective clothing, eyeprotection, respiratory protection, and air sampling as necessary tocheck the effectiveness of the control program.

(3) Pump rating curves and complete mixer details, includingphotographs or drawings of the proposed mixing equipment, shall besubmitted to the Contracting Officer for approval 30 days prior touse. The Contracting Officer shall have the right to require theContractor to make changes in the equipment which the ContractingOfficer determines necessary to make the equipment performsatisfactorily during the grouting operations without additional costto the Government

(4) The Contractor shall submit test results from testing ofcylinders in accordance with the requirements of subparagraph c.below.

c. Quality assurance. - Quality assurance shall be in accordance withparagraph 1.4 and these specifications. Unless otherwise directed, groutmixtures shall be proportioned in accordance with ASTM C 938.

M-47 (M0470000.896)Page 12 of 738-1-96

12

For normal structural work, the ratio of cementitious materials (cementplus pozzolan) to sand shall be 1:1. If leaner mixes are required(generally for low heat generation), the ratio may be adjusted, but shallnot exceed 1:2.

The ratio of cement to pozzolan, by weight, shall be between 2:1 and 4:1as directed by the Contracting Officer.

The ratio of water to cementitious materials

W P+C where:

W = weight of waterP = weight of pozzolanC = weight of concrete

shall not exceed 0.50 by weight. For severe exposure conditions, theW/P+C ratio shall be in accordance with Reclamation's "Concrete Manual,"Eighth Edition, revised, chapter III, table 15.

The pumpability of grout containing fine sand (grading 1, table 2 of ASTMC 637) shall be controlled by the consistency test using the flow cone inaccordance with ASTM C 939. The flow time shall be between 20 and30 seconds unless it can be demonstrated that grout can be effectivelypumped at a different flow time.

Compressive strength cylinders shall be cast in accordance with ASTM C943 and tested at 7 and 28 days' age with a minimum of two cylinderstested for each age. The design compressive strength of PAC shall be4,000 pounds per square inch at 28 days' age. The required averagestrength for PAC is that which will ensure that 80 percent of all testcylinders exceed the design strength.

The quality of the top of formed PAC placements shall be ensured byventing air, water, and low-quality grout from the uppermost location inthe placement.

For unformed surfaces where a screeded or troweled finish is required,the grout level shall flood the top surface above any aggregate, and anydiluted grout shall be removed by brooming. A thin layer of pea gravelhaving a maximum-size aggregate (MSA) of 3/8 inch shall be worked intothe surface by raking and tamping or internal vibration. The surfaceshall be finished in accordance with conventional concrete procedures toresemble the finish of the surrounding concrete. Care shall be takenwhen topping off the unformed surface to avoid lifting or loosening ofthe surface aggregate.

d. Materials. - Materials for PAC shall be in accordance with therequirements of ASTM C 938 and the following additional requirements:

(1) Pozzolan. - Pozzolan shall meet the requirements of ASTM C 618for class F pozzolan.

(2) Admixtures. -

(a) Air-entraining admixture. - Air-entraining admixture (AEA)shall meet the requirements of ASTM C 260.

M-47 (M0470000.896)Page 13 of 738-1-96

The amount of AEA used for injecting mortar shall be that amountnecessary to effect a total air content in the mortar, prior toinjection, of 9 percent, plus or minus 1 percent, by volume ofmortar.

(b) Grout fluidifier. - Grout fluidifier shall meet therequirements of ASTM C 937.

(c) Chemical admixtures. - Chemical admixtures, if permitted,shall meet the requirements of ASTM C 494 for types A, D, F, or Gadmixtures. Chemical admixtures shall not be used without priorapproval from the Contracting Officer.

(3) Sand. - Sand shall consist of natural particles which may besupplemented by limited quantities of crushed sand to make up fordeficiencies in the natural materials. Natural sand is required dueto its favorable particle shape for pumping grout. Sand for PACdiffers from sand used for conventional concrete, primarily in itsfiner grading.

Sand shall meet the quality requirements of subparagraph 3.6.d.; andthe grading requirements of ASTM C 938.

(4) Coarse aggregate . - Coarse aggregate shall be clean and well-graded. Unless otherwise directed, the MSA shall be 1-1/2 inches, andafter compaction in the forms, shall have a voids content from 35 to45 percent.

Coarse aggregate shall meet the quality requirements of subparagraph3.6.d.; and, the grading requirements of ASTM C 637, table 2,grading 1 for coarse aggregate.

For larger placements, the largest size aggregate that caneconomically be placed shall be used. The MSA and grading of coarseaggregate for these placements should follow the guidelines of ACI304.

e. Safety. - All work shall be performed in accordance with requirementsof paragraph 1.6 and these specifications.

The Contractor shall comply with Reclamation's "Construction SafetyStandards" as well as all other applicable safety and health standardsand regulations. In the event of conflict, the more stringent standardshall apply.

f. Concrete preparation. - The Contractor shall prepare all concretesurfaces and foundations for PAC application. Concrete surfacepreparation shall be in accordance with subparagraph 3.6.f.

For underwater repairs, high-pressure water jetting shall be the normalmethod for concrete removal and surface scarification. Low-pressurewater jetting will be allowed for cleanup immediately before placing PAC.

In underwater construction where contamination is known or suspected toexist, the water shall be sampled and tested to determine the degree ofcontamination and its possible influence on the quality of concrete. Where moderate contamination is present, concrete surfaces shall becleaned within 2 days prior to placing aggregate and grouting. Ifcontaminants are present in such quantity or are of such character that

M-47 (M0470000.896)Page 14 of 738-1-96

14

harmful effects cannot be eliminated or controlled, preplaced aggregateconcrete shall not be used.

All loose, fine material shall be removed from the placement insofar aspossible before placement of coarse aggregate to prevent subsequentcoating of the aggregate or filling of voids.

g. Application. -

(1) General. - Application of PAC shall include construction andplacement of formwork and the grout injection system, placement ofaggregate, injection of grout, finishing, and curing of PAC.

(2) Equipment. - The grout mixing, pumping, and injection systemshall be furnished by the Contractor.

The grout injection system shall be designed to deliver and injectgrout into the preplaced aggregate, to provide a means for determiningthe grout elevations within the aggregate mass, and to provide ventsin enclosed forms for water and air to escape. The injection systemshall have a bypass for returning grout to an agitating tank.

Pumps shall be of a positive displacement type and be equipped with apressure gauge on the outlet line to indicate any incipient lineblockage. At least one extra pump shall be on standby to maintaincontinuous pumping operations. The pumps shall have quick-disconnecting fittings to the grout supply line.

Mixing and agitating equipment shall be sized to maintain acontinuous, uninterrupted flow of grouting mortar for the duration ofthe PAC placement. The mixing plant shall be a high-speed centrifugaltype and shall be equipped with an accurate water meter, reading cubicfeet to tenths of a cubic foot. In addition to the grout mixer, aholdover mechanical agitator tank of similar volume as the mixer shallbe provided. Suitable provisions shall be made for passing the groutthrough a U.S. Standard 2.36-mm (No. 8) sieve as it is discharged fromthe mixer.

The batching and mixing plant equipment shall accurately measure theamounts of cement, pozzolan, sand, admixtures, and water batched forgrout. Inaccuracies in feeding and measuring during operation shallnot exceed by individual weight plus or minus 1 percent for water;plus or minus 2 percent for cement, pozzolan, or sand; and plus orminus 3 percent for admixtures.

The length of delivery line shall be kept to a practicable minimum. Pipe sizes shall be designed so that during operation, the groutvelocity ranges between 2 and 4 feet per second for delivery lines upto 300 feet, or at a pumping rate of about 1 cubic foot of grout perminute through a 1-inch-diameter pipe. Pipe sizes shall beapproximately 1 inch in diameter, but may need to be increased in sizefor delivery lines longer than 300 feet to reduce pressures.

Grout insert pipes shall have a diameter of 3/4 to 1 inch and shall beplaced vertically, horizontally, or at angles to inject grout at theproper location. Grout insert pipes shall be in sections about5-1/2 feet in length for ease of withdrawal. For depths greater than15 feet, grout insert pipes shall be flushed coupled. For depths lessthan 15 feet, standard pipe couplings may be used.

M-47 (M0470000.896)Page 15 of 738-1-96

Connections between grout delivery lines and insert pipes shall havequick-disconnect fittings. Quick-disconnect fittings which reduce thecross section of the flow area shall not be used. Each insert pipe,or the end of the delivery line where it attaches to the insert pipe,shall be equipped with an individual valve to control or stop the flowof grout. Valves shall be of a quick-opening, plug type which canreadily be cleaned.

For vertical and angled injection tube placements, sounding wellsshall be used to determine the level of grout in the placement. Sounding wells shall consist of slotted pipe with a diameter of about2 inches. A 1-inch-diameter float, weighted so that it will float ongrout and sink in water (for underwater placements), shall be attachedto a sounding line and float freely in the sounding well.

(3) Formwork. - Forms for PAC may be of wood, steel, or othermaterials suitable for conventional concrete. Wood forms or othermaterials which may swell or become damaged by submergence in watershall not be used for underwater repairs.

Joints and any entry holes for bolts, reinforcement, injection ports,vents, or injection wells shall be caulked to eliminate grout leakage.

Forms shall be designed to resist the lateral pressure exerted byaggregates during and after placing, and to resist full hydraulicpressure of the concrete throughout placing until initial setting hasbegun.

Form vibrators for consolidation shall be mounted so that vibrationdoes not loosen bolts and joints which may lead to grout leakage orfailure. Form vibrators shall be mounted on ribs or stiffenersattached to the sheathing to effectively transmit vibration to theconcrete.

All forms shall be coated with a suitable bond breaker for ease ofremoval without damaging concrete. For underwater repairs, the bondbreaker shall be selected so that it does not wash off the formsduring submergence. Formwork, injection tubing, inspection wells, andother equipment shall be protected from damage by aggregates duringplacing.

Reinforcing steel shall be installed during construction of formworkand securely held in place during placement of aggregate and injectionof grout.

(4) Grout pipe system. - The grout pipe system shall be furnished bythe Contractor and shall consist of a series of regularly spacedinjection tubes with outlets beginning at the bottom and continuing tothe top of the compacted aggregates. Observation wells shall bespaced at regular intervals between the injection tubes. Vent pipesshall be used in forms that contain restricted or irregular spaceswhere water or air may be entrapped by the rising grout surface, suchas blockouts or embedment work.

The grout pipe system shall be designed to inject grout beginning atthe lowest point in the PAC placement and continue to raise the groutlevel within the mass by selectively withdrawing the pipes andswitching to other pipes to maintain the grout at a gently sloping tonearly horizontal level. The grout pipe system shall be coded to

M-47 (M0470000.896)Page 16 of 738-1-96

16

clearly identify the location of the outlet of the pipe supplyinggrout and the order of supplying grout to the pipes.

The spacing of grout insert pipes shall be between 4 and 12 feet andshould average approximately 6 feet. The outlet of grout insert pipesshall begin not more than 6 inches above the bottom of the aggregatemass. Rows of horizontal pipes should be not more than 6 inches abovethe next lower row of pipes.

As a guide for layout of insert pipes, it can be assumed that thegrout surface will have a 1:4 (vertical to horizontal) slope in thedry and a l:6 slope under water.

For vertical and inclined injection systems, sounding wells shall bespaced to observe the level of grout. The ratio of number of soundingwells to insert pipes shall be between 1:4 and not less than 1:10. Sounding wells shall be placed vertically or near vertically.

The delivery line shall consist of a single pipeline extending fromthe pump to the insert pipe equipped with a valve, or to a wyebranching to two insert pipes equipped with valves at the beginning ofthe wye and at both outlets. A manifold system in which more than onegrout insert is operative at the same time shall not be used.

(5) Aggregate preparation and placement. - Coarse aggregate shall bewashed and screened immediately before placing in the forms. If morethan one size of coarse aggregate is used, the aggregate shall bebatched and mixed in the proper proportions or discharged atproportional rates onto a vibrating deck or revolving wash screens.

Coarse aggregate shall be transported to the forms by buckets,conveyors, or other approved methods. Coarse aggregates shall bedumped as close as possible to their final location. A flexiblerubber elephant trunk (tremie) shall be used to limit free fall toless than 5 feet to minimize segregation and breakage of aggregate. For large placements, a gated pipe with a diameter at least four timesthe MSA shall be used. The pipe shall be gradually filled and loweredtoward the point of placement, and after the pipe is completely filledat the upper end, aggregate shall be discharged from the lower gate. Aggregate shall not be discharged through an unfilled or partiallyfilled pipe.

Coarse aggregate shall be dumped and spread in nearly horizontallifts, each lift not to exceed 1 foot in height. Around closelyspaced embedded items, such as reinforcing steel, conduits, andblockouts, and in more difficult placements where high density andexceptional homogeneity of concrete are desired, the lift height shallbe limited to no more than 4 inches and may have to be placed by hand. Vehicular traffic shall not be permitted on top of preplaced coarseaggregate, with the exception of small skips or loaders and only withapproval of the Contracting Officer. This equipment shall have rubbertires and be cleaned of any loose debris or substances that maycontaminate aggregates or interfere with grout travel duringinjection.

Although coarse aggregate shall be completely washed prior to placingit shall not be flushed with water in the forms for the purpose ofwashing.

M-47 (M0470000.896)Page 17 of 738-1-96

If water is used for the purpose of precooling aggregate or to providelubrication for grout, the water shall be injected through thepreplaced grout insert pipes rather than on top of the aggregates.

(6) Grout injection. - Injection shall begin at the lowest insertpipe point within the form and continue to raise the level of groutevenly to the top of the mass of aggregate. The injection processshall raise the level of grout approximately 18 to 24 inches above theoutlet of the insert pipe before withdrawing of that pipe begins. Thereafter, the level of grout shall remain a minimum of 12 inchesabove the outlet of the insert pipe until the injection is completed.

Grouting shall proceed at only one insert pipe at a time. If a wye ormanifold system is used, the system shall be equipped with individualvalves to control the flow to each insert pipe.

Before the insert pipe is withdrawn, the valve at the pipe inlet shallbe shut off. The delivery pipe may then be disconnected to inject atother locations.

When injection insert pipes are placed horizontally, the process shallbegin at the lowest insert pipe. Adjacent insert pipes shall havevalves opened both alongside and above the pipe being injected. Whengrout begins to flow out of these pipes, they shall be shut off andgrouting continued so that the adjacent pipes are completelysubmerged. The initial pipe shall then be shut and the process shallbe repeated, traveling in a horizontal direction before proceeding tothe upper row.

Grout shall not be allowed to set up in the insert pipes betweeninjections. If the injection process is expected to continue for anextended period, a suitable retarding admixture shall be used in thegrout. Vertical insert pipes may be rodded to remove grout prior toreinjection; however, insert pipes shall not be cleaned by injectingwater through them.

The rate of grout rise and rate of grout injection shall be controlledwithin the form so that excessive form pressures are not created andso that grout does not cascade within the mass. This is particularlyimportant when grouting under water to avoid sand streaks andhoneycombing within the mass.

When grouting around embedded items and particularly under flatsurfaces or recessed areas, the grout shall be injected until goodquality grout is forced from vent pipes. Good quality grout shall begrout that is not diluted and free from sand, silt, trash, and otheritems. The rate of flow of grout and grout injection pressures shallbe closely monitored in enclosed locations to avoid form failure.

Form vibration shall be used to consolidate grout and remove entrappedair pockets adjacent to form surfaces. Excessive form vibration whichcauses sand streaking shall not be done. Internal vibration shall notbe used for consolidation of the aggregate-grout mixture, but may beused for topping off unformed surfaces.

Unplanned construction joints shall not be used without approval fromthe Contracting Officer. If a breakdown occurs that stops placement,the grout insert tubes shall be withdrawn, and the grout surface shallbe considered a cold joint. Cold joints shall be treated by firstremoving coarse aggregate down to the joint surface, removing

M-47 (M0470000.896)Page 18 of 738-1-96

18

aggregate and poor-quality mortar, and then cleaning the joint surfaceby approved methods, taking care not to undercut exposed aggregates.

h. Curing. - Curing and protection of PAC shall be in accordance withsubparagraph 3.6.h.

3.5 SHOTCRETE

a. General. - Shotcrete is defined as pneumatically applied concrete ormortar placed directly onto a surface. The shotcrete shall be composedof water, cementitious materials, sand, coarse aggregate, steel fibers(if specified), and admixtures, and shall be placed by either the dry-mixor wet-mix process as specified herein.

The dry-mix process shall consist of thoroughly mixing the solidmaterials; feeding these materials into a mechanical feeder or gun;carrying the materials by compressed air through a hose to a specialnozzle; introducing the water and intimately mixing it with the otheringredients at the nozzle; and then jetting the mixture from the nozzleat high velocity onto the surface to receive the shotcrete.

The wet-mix process shall consist of thoroughly mixing all theingredients with the exception of the accelerating admixture, if used;feeding the mixture into the delivery equipment; delivering the mixtureby positive displacement or compressed air to the nozzle; and thenjetting the mixture from the nozzle at high velocity onto the surface toreceive the shotcrete.

The equipment used by the Contractor for mixing and applying shotcreteshall be capable of handling and applying shotcrete containing thespecified maximum-size coarse aggregate. All equipment, includingmixers, hoses, nozzles, nozzle liners, air- and water-pressure gauges,and gaskets, shall be maintained in clean and proper operating conditionsatisfactory to the Contracting Officer.

b. Submittals. - The Contractor shall submit for approval to theContracting Officer a proposed specific operating procedure including ahazard analysis for all shotcrete operations. The specific operatingprocedure shall include such things as engineering controls, protectiveclothing, eye protection, respiratory protection, and air sampling asnecessary to check the effectiveness of the control program.

The Contractor shall submit the specimens extracted from panelsfabricated for preapplication testing.

The Contractor shall submit test specimens of fresh and hardened concretefrom locations directed by the Contracting Officer.

c. Quality assurance. - Quality assurance shall be in accordance withparagraph 1.4 and these specifications. The Government will perform alltesting of fresh and hardened shotcrete. The Contractor shall obtainspecimens from locations specified by the Government. The compressivestrength of the shotcrete will be determined through the medium of testsof 3- by 3-inch cores or 3-inch cubes. The average compressive strengthof specimens taken from a shotcrete application shall be not less than:

(1) Four thousand pounds per square inch at 28 days' age.

(2) Six hundred pounds per square inch at 8 hours' age. This will bedetermined from 3-inch cubes extracted from test panels.

M-47 (M0470000.896)Page 19 of 738-1-96

Adjustments shall be made as directed by the Contracting Officer toobtain shotcrete having suitable impermeability, strength, density, anddurability. Suitable strength is that which will ensure that 80 percentof all test specimens exceed or equal the average strength as specifiedabove.

(3) Preapplication testing of shotcrete and nozzlemen. - No shotcreteshall be applied to the work until preapplication testing indicatesthat the nozzleman is qualified and the proposed shotcrete mixturemeets the specified compressive strength. The Contractor shall allowadequate lead time for fabricating of test panels and testingshotcrete specimens. Furthermore, the Contractor is encouraged tofabricate panels for several mixtures since failure of a singlemixture to meet specified strength requirements could delayaccomplishment of other work.

(a) Shotcrete mixture. - At least 30 days prior to application ofshotcrete to the work, the Contractor shall fabricate two testpanels for each mixture to be used for vertical and overheadpositions of application.

Application of shotcrete to test panels may be accomplished atlocations other than the construction site provided:

(aa) Equipment used for fabricating test panels is identical tothat to be used in application.

(bb) The materials used in fabricating test panels are from thesame sources as those to be used in application and meet allspecifications requirements.

(cc) Application is made in the presence of the ContractingOfficer by a nozzleman who will later apply the shotcrete to thework.

Test panels shall be fabricated by applying shotcrete in oneapplication not less than 4 inches thick to a panel form made ofplywood or other suitable material.

The panel form to be used for vertical and overhead applications shallbe either of two types as follows:

(dd) Open ended on at least two sides with 90E edges on enclosedsides. The minimum size of this open-ended panel shall be 18inches square.

(ee) Enclosed on all four sides with members that taper outward ina manner that prevents the accumulation of rebound at edges andcorners while allowing a shotcrete thickness of not less than 4inches over the entire flat area of the panel. The minimum size ofthe center flat area of panels enclosed by tapered edges shall be15 inches square.

Panels should be stiffened and weighted sufficiently to provide rigidsurfaces against which the shotcrete can be applied. The panels shallcontain the same type of reinforcement as to be used in constructionto indicate whether sound shotcrete is obtained without shadowingbehind the reinforcement.

M-47 (M0470000.896)Page 20 of 738-1-96

20

After fabrication, the panel shall, except when test specimens arebeing obtained, be covered and sealed with polyethylene sheeting orshall be cured by any other approved method that will prevent loss ofmoisture.

The Contractor shall provide all necessary equipment and shall obtain3-inch cubes from the test panels for testing the compressive strengthat 8 hours' age and shall obtain 3-inch cubes or 3-inch-diameter coresfrom test panels for testing the compressive strength at 28 days' age.

All core drilling and saw cutting of cubes shall be performed in aworkmanlike manner by competent and experienced workmen. Testspecimens shall be extracted at the latest time, satisfactory to theContracting Officer, that the specimens can be delivered by theContractor to the Government for testing at the specified age. Atleast five specimens shall be obtained from each of the panels foreach mixture being verified. Extreme care shall be taken in drillingcores or cutting cubes to obtain specimens satisfactory to theContracting Officer.

Cores shall be 3 inches in diameter, drilled the full depth of theshotcrete; they shall be straight, sound, of uniform diameter, and ofsufficient length for subsequent trimming by the Contractor to producea right cylinder with an L/D ratio of 1.0 plus or minus 0.03.

Cubes shall be cut full depth of the shotcrete, shall be sound, andshall have six uniform square sides of 3-inch length plus or minus0.05 inch.

Immediately after extraction, test specimens shall be individuallywrapped and sealed in polyethylene bags or covered and sealed by anyother approved means to prevent loss of moisture. Each test specimenshall be properly marked for identification.

Each set of test specimens shall be delivered without delay to theproject laboratory, or other location approved by the ContractingOfficer, for testing at the specified age.

(b) Shotcrete nozzleman. - The nozzleman who applies shotcrete shallbe certified with the materials and equipment to be used for the work. Certification shall be in accordance with ACI 506.3R with thefollowing limitations:

(aa) The certification examination will be conducted by authorizedrepresentative of the Contracting Officer.

(bb) The examination will consist of an oral test and a fieldworkmanship demonstration test.

(cc) The test panels shall be a minimum of 18 inches square and4 inches deep. The sides may have beveled edge forms (45E angleout to reduce the entrapment of rebound in the corners).

(dd) Test specimens shall be of the size and shape specified forquality control in these specifications.

d. Materials. -

M-47 (M0470000.896)Page 21 of 738-1-96

(1) Portland cement. - The cementitious materials in shotcrete shallcomply with subparagraph 3.6.d.(1), with the exception that type IIIcement may be approved for use if sulfate conditions do not exist.

(2) Water. - Water shall be in accordance with subparagraph3.6.d.(4).

(3) Sand and coarse aggregate. - Except as hereinafter provided forcoarse aggregate grading, the sand and coarse aggregate shall be inaccordance with subparagraph 3.6.d.(5).

The maximum-size coarse aggregate shall be no larger than 3/8 inch. No material retained on the 3/8-inch sieve shall be permitted. Only3 percent significant undersize aggregate material that will pass a4.75-mm (No. 4) U.S. Standard sieve will be permitted.

(4) Admixtures. - Admixtures shall be in accordance with subparagraph3.6.d.(3).

(a) Accelerator. - The Contractor may use an acceleratingadmixture in shotcrete.

(b) Air-entraining admixture. - The amount of air-entrainingadmixture used for the wet-mix process shall be that amountnecessary to effect a total air content in the shotcrete, prior toapplication, of 7 percent plus or minus 1 percent by volume ofshotcrete.

(5) Steel fibers. - Where directed by the Contracting Officer, theContractor shall furnish steel fibers for reinforcement. The amountof steel fibers used shall be 90 pounds of fiber per cubic yard ofshotcrete.

Steel fibers shall be carbon steel deformed type I (cold drawn wire)or type II (cut sheet) to conform to the requirements of ASTM A 820. Length of steel fiber shall be 3/4-inch minimum to 1-1/4-inch maximum. The length divided by diameter (or equivalent diameter), or aspectratio, shall be 45 minimum and 100 maximum. The steel fiber shallhave a minimum average tensile strength of 50,000 pound-force persquare inch.

(6) Curing compounds. - Curing compounds shall meet the applicablerequirements of subparagraph 3.6.d.(6).


f. Concrete preparation. - Concrete to be repaired with shotcrete shallbe prepared in accordance with section 2.

g. Application. -

(1) Mixture proportions. - The proportions of water, cementitiousmaterials, sand, coarse aggregate, and admixture and fibers, if used,shall be determined by the Contractor subject to approval by theContracting Officer to obtain the specified compressive strength andbond. The shotcrete shall have a minimum cementitious materialscontent of 658 pounds per cubic yard, as discharged from the nozzle. Furthermore, the amount of cementitious materials will be increased by

M-47 (M0470000.896)Page 22 of 738-1-96

22

the Contracting Officer as necessary to obtain the specifiedcompressive strengths and bond.

(2) Consistency. - The consistency of the dry-mix process shotcreteshall be regulated by the amount of water introduced at the nozzle andshall be adjusted so that the in-place shotcrete is adequatelycompacted and neither sags nor shows excessive rebound.

The consistency of the wet-mix process shotcrete at the delivery pointshall not exceed a 3-inch slump.

(3) Batching. - Batching for the dry-mix process shall be asspecified in this paragraph. Water, cementitious materials, sand,coarse aggregate, admixture, and fibers shall be volume proportionedby controlled, calibrated, screw conveyor, or other methods of feed,provided uniform proportions are obtained. The equipment shall becapable of controlling the delivery of material so that inaccuraciesdo not exceed 1 percent for water; 1-1/2 percent for cementitiousmaterials; 2 percent for sand and coarse aggregate; and 3 percent foradmixture and fibers. If these limits cannot be consistently met,then batching shall be by direct weighing.

To ensure accurate, consistent proportioning of aggregate, augers usedin dry-mix process shotcrete delivery equipment shall be constructedof abrasion-resistant material to prevent rapid and excessive wear. Auger feed shall be recalibrated as necessary to keep them within theprescribed batching accuracy percent.

The percentage of surface moisture in the sand (ASTM C 566) shall be3 to 6 percent, by weight, and shall be controlled within this rangeas may be necessary to maintain uniform feed and to avoid choking thedelivery equipment.

Shotcrete batches containing cementitious materials that have been incontact with damp aggregate or other moisture for more than 2 hoursshall be wasted at the Contractor's expense.

Batching for the wet-mix process shall be in accordance with therequirements for concrete batching under subparagraph 3.6.g.

When batching with fibers the Contractor shall obtain a good blend offibers throughout the shotcrete. The Contractor shall furnishappropriate equipment or develop a suitable technique for dispersingthe fibers in the mixer free of fiber clumps. A suggested guide isACI 544.3R.

(4) Mixing. - Mixing for the wet-mix and the dry-mix process shall beas specified in this paragraph. Cementitious materials, sand, coarseaggregate, admixtures, and steel fibers shall be uniformly added andthoroughly mixed by machine before being fed into the deliveryequipment.

Mixers used to mix dry ingredients shall discharge the batch withoutsegregation. Mixers shall be tested for uniformity of coarseaggregate content from front to back of the mixer. The maximumpermissible difference in percentage of coarse aggregate by weight ofsample shall not exceed 6 percent within a batch.

The discharge nozzle for the dry-mix process shall be equipped with amanually operated water injection system of sufficient pressure to

M-47 (M0470000.896)Page 23 of 738-1-96

provide an even distribution of water into the dry shotcrete mixtureat the nozzle. The water valve shall be capable of ready adjustmentto vary the quantity of water and shall be convenient to thenozzleman.

(5) Placing. - Placing shotcrete shall be performed only by anozzleman certified in accordance with subparagraph 3.5.c.(3) duringpreapplication testing.

An air compressor with ample capacity to provide clean, dry air andmaintain a uniform nozzle velocity shall be used for applyingshotcrete.

The shotcrete shall be applied by pneumatic pressure from a dischargenozzle held about 2 to 5 feet from the surface and in a stream asnearly normal as possible to the surface being covered. The nozzleshall also be rapidly gyrated while applying the shotcrete.

The shotcrete shall be applied in layers having a thickness that willensure complete adherence of the shotcrete to the surface. Anyshotcrete that shows evidence of sloughing or separation shall beremoved and replaced by and at the expense of the Contractor and tothe satisfaction of the Contracting Officer.

Care shall be taken to prevent the formation of sand pockets in theshotcrete. Any sand pockets formed shall be removed immediately andreplaced with suitable shotcrete at the expense of the Contractor.

Use of rebound as shotcrete aggregate is not permitted, and reboundaccumulations shall be removed and disposed of at the expense of theContractor as approved by the Contracting Officer.

The temperature of shotcrete, as placed, shall be between 50 and 90EF. Shotcrete shall not be applied to frozen surfaces. The appliedshotcrete shall be kept at a temperature of at least 50 EF for aminimum of 3 days immediately following application. When coldweather conditions prevail at the job site and the temperature ofaggregates and water is below 50 EF, it may be necessary to heat theaggregate and/or water prior to use in the shotcrete to obtainshotcrete meeting the specified 28-day compressive strength.

The Contractor shall provide and maintain sufficient standby equipmentto assure continuous production and application of shotcrete.

If, in the Contracting Officer's opinion, the shotcreting systemselected by the Contractor fails to provide satisfactory in-placeshotcrete in accordance with these specifications, the Contractorshall change to another system of either of the two processes, providea redemonstration of the nozzleman's proficiency, or provide a newqualified nozzleman.

If, in the Contracting Officer's opinion, the projection of steelfibers (when used) on the face of the finished shotcrete creates ahazard to personnel, a sacrificial coating of no less than 1/2-inchthickness of shotcrete without the steel fibers shall be applied.

h. Curing. - Shotcrete that is applied where the ambient relativehumidity is 85 percent or above will not require measures to control theevaporation of water during curing. However, the Contractor shallsubstantiate that the relative humidity level in the area of application

M-47 (M0470000.896)Page 24 of 738-1-96

24

is above 85 percent by furnishing, installing, and maintaining equipmentcapable of continuously recording relative humidity.

When the relative humidity is less than 85 percent, the Contractor shallinitiate an approved curing method immediately after application of theshotcrete.

Curing shall be accomplished by either:

(1) Raising and maintaining the ambient relative humidity above85 percent, or

(2) Applying a membrane curing compound as specified in subparagraph3.6.d.(6).

Water curing. - Shotcrete cured with water shall meet the applicablerequirements of subparagraph 3.6.h. except the 14-day requirement may bereduced to 7 days.

3.6 CONCRETE REPLACEMENT

a. General. - Concrete replacement shall be used on areas of damaged orunacceptable concrete greater than 1 square foot having a depth greaterthan 6 inches or a depth extending 1 inch below or behind the backside ofreinforcement. Concrete replacement shall also be used for holesextending entirely through concrete sections and for large areas ofrepair greater than 4 inches in depth when the concrete to be repaired isless than 7 days old. Epoxy bonding agents, latex bonding agents, dryneat cement, cement paste, or cement and sand mortar shall not be used tobond fresh concrete to concrete being repaired by this method.

b. Submittals. - The Contractor shall submit certification of compliancefor materials in accordance with subparagraph d. below.


d. Materials. - All concrete materials shall be obtained from previouslytested and approved sources. Materials will be accepted on certificateof compliance with the following ASTM Standards:

(1) Portland cement. - Portland cement shall meet the requirements ofASTM C 150 for type I, II, or V cement. The specific cement typeshall be as directed by the Contracting Officer and determined by theenvironment in which the repair is conducted.

(2) Pozzolan. - Pozzolan shall meet the requirements of ASTM C 618for class F pozzolan.

(3) Admixtures. - The Contractor shall furnish air-entraining andchemical admixtures for use in concrete.

(a) Air-entraining admixture shall be used in all concrete andshall conform to ASTM C 260.

(b) Chemical admixtures. - The Contractor may use type A, D, F, orG chemical admixtures. If used, they shall conform to ASTM C 494.

M-47 (M0470000.896)Page 25 of 738-1-96

(4) Water. - The water used in making and curing concrete shall befree from objectionable quantities of silt, organic matter, salts, andother impurities.

(5) Aggregate. - The term "sand" is used to designate aggregate inwhich the maximum size particle will pass a 4.75-mm (No. 4) sieve. The term "coarse aggregate" is used to designate all aggregate whichcan be retained on a 4.75-mm (No. 4) sieve. Sand and coarse aggregatemeeting the requirements of ASTM C 33 shall be used in all concrete.

(6) Curing compound. - Wax-base (type I) and water-emulsified resin-base (type II) curing compounds shall conform to the requirements ofReclamation's "Specifications for Concrete Curing Compound" (M-30)dated October 1, 1980.

e. Safety. - All work shall be performed in accordance with paragraph1.6.

f. Concrete preparation. - After damaged or unacceptable concrete hasbeen removed as specified in section 2. the surface on which thereplacement concrete will be placed shall be prepared. An acceptablesurface shall have the appearance of freshly broken, properly curedconcrete. The surface shall be free of any deleterious materials such asfree moisture, ice, petroleum products, mud, dust, carbonation, and rust. The perimeters of the repair shall be saw cut to a minimum depth of 1inch.

The clean surface is not ready to receive repair concrete until it hasbeen brought to a saturated, surface-dry condition. This condition isattained by saturating the surface to a depth that no concrete mixturewater may be absorbed from the fresh concrete. Then, just prior toplacing concrete against the surface, all free moisture (moisture capableof reflecting light) shall be removed from the prepared surface.

g. Application. - Replacement concrete shall be composed of cement,coarse aggregate, sand, water, and approved admixtures, all well mixedand brought to the proper consistency. Concrete mixtures shall beproportioned in accordance with Reclamation's "Concrete Manual", EighthEdition, revised, chapter III. The water-cement ratio of the concrete(exclusive of water absorbed by the aggregates) shall not exceed 0.47 byweight. Slump of the concrete, when placed, shall not exceed 2 inchesfor concrete in slabs that are horizontal or nearly horizontal and 3inches for all other concrete. Concrete with less slump should be usedwhen it is practicable to do so. The concrete ingredients shall bethoroughly mixed in a batch mixer. The concrete, as discharged from themixer, shall be uniform in composition and consistency from batch tobatch.

(1) Forms. - Forms shall be used for concrete whenever necessary toconfine the concrete and shape it to the required lines. The formsshall be clean and free from encrustations of mortar, grout, or otherforeign material. Before concrete is placed, the surfaces of theforms shall be coated with a form oil that will effectively preventsticking and will not soften or stain the concrete surfaces or causethe surfaces to become chalky or dust producing.

(2) Placing. - Placing of concrete shall be performed only in thepresence of an authorized representative of the Contracting Officer. Placement shall not begin until all preparations are complete and theauthorized representative of the Contracting Officer has approved the

M-47 (M0470000.896)Page 26 of 738-1-96

26

preparations. Concrete shall not be placed in standing or runningwater unless, as determined by the Contracting Officer, the structureunder repair cannot be economically dewatered. If underwater concreteplacement is required, special placing procedures shall be required. A suggested guide is ACI 394R.

When appropriate, concrete shall be placed in layers not greater than20 inches thick. Each layer, regardless of the thickness, shall beadequately consolidated using immersion-type vibrators or formvibrators when approved. Adequate consolidation of concrete isobtained when all undesirable air voids, including the air voidstrapped against forms and construction joints, have been removed fromthe concrete.

(3) Finishing. - The class of finish required shall be a finishclosely resembling the finish of the surrounding concrete.

h. Curing and protection. - Concrete repairs shall be cured either bywater curing or by use of wax-base (type I) or water-emulsified resin-base (type II) curing compound meeting the requirements of subparagraph3.6.d.(6). Daily inspection by the Contractor shall be performed toensure the maintenance of a continuous, water-retaining film over therepaired area. The water-retaining film shall be maintained for 28 daysafter the concrete has been placed.

Water curing shall commence when the concrete has attained sufficient setto prevent detrimental effects to the concrete surface. The concretesurface shall be kept continuously wet for 14 days.

The Contractor shall protect all concrete against damage until acceptanceby the Government. Whenever freezing temperatures are imminent, theContractor shall maintain the newly placed repair concrete at atemperature of not less than 50 EF for 72 hours. Water-cured concreteshall be protected from freezing for the duration of the curing cycle andan additional 72 hours after the water is removed.

3.7 EPOXY-BONDED EPOXY MORTAR

a. General. - Epoxy-bonded epoxy mortar is defined as freshly mixedepoxy mortar (sand with epoxy binder) that is placed over an epoxy resinbond coat on hardened existing concrete. Epoxy-bonded epoxy mortarrepair may be used when the depth of repair is 1-1/2 inches or less. This method may also be used for repair of areas with a depth greaterthan 1-1/2 inches when those areas are small (less than 1 square foot)and few in number, and where it is impractical to use epoxy-bondedconcrete.

Epoxy-bonded epoxy mortar may be used only when:

(1) Moisture in the structure will not collect behind the bond coatand cause damage upon freezing, and

(2) The repair will not be subjected to extremes of temperatures suchas those caused by exposure to direct sunlight, extremes of climate,or extremes in water temperature.

All epoxy-bonded epoxy mortar repairs to new construction shall beperformed after 7 days from the original placement.

b. Submittals. -

M-47 (M0470000.896)Page 27 of 738-1-96

(1) When directed by the Contracting Officer, the Contractor shallsubmit samples of the epoxy-resin bonding system. The samples shallbe submitted at least 30 days prior to use in the work to the Bureauof Reclamation, Attn D-8180, Building 56, Denver Federal Center, WestSixth Avenue and Kipling Street, Denver CO 80225.

(2) Certification of epoxy-bonding agent. - The Contractor shallfurnish the Contracting Officer the manufacturer's certification ofconformance of the epoxy-resin bonding system with thesespecifications. The certification shall identify the Reclamationsolicitation/ specifications number(s) under which the epoxy is to beused and shall include the quantity represented, the batch numbers ofthe resin and curing agent, and the manufacturer's results of testsperformed on the particular combination of resin and curing agent.


d. Materials. -

(1) Epoxy resin. - The same epoxy resin system shall be used for boththe bond coat and the epoxy mortar. The epoxy resin shall meet therequirements of specifications ASTM C 881 for a type I , grade 2,class B or C or a type III, grade 2, class B or C epoxy system. Inaddition, it shall be a 100-percent solids system, and no unreactivediluents, wetting agents, or volatile solvents shall be incorporated.

(2) Sand. - The sand for epoxy mortar shall be clean, dry, well-graded sand composed of sound particles passing a 1.18-mm (No. 16)sieve and conform to the following limits:

* * Individual percent, Sieve * by weight, retained * on sieve * * 600 µm (No. 30) * 26 to 36 300 µm (No. 50) * 18 to 28 150 µm (No. 100)* 11 to 21 pan * 125 to 35 *

1Range shown is applicable when 60 to 100 percent of pan is retainedon the 75 µm (No. 200) sieve. When 0 to 59 percent of pan isretained on the 75 µm (No. 200) sieve, the percent pan shall bewithin the range of 10 to 20 percent, and the individualpercentages retained on the 600 µm, 300 µm, and 150 µm (Nos. 30,50, and 100) sieves shall be increased proportionately.

Sand of this grading is not usually commercially available and mayhave to be produced by the Contractor. Starting with a concrete sand,the oversized particles shall be removed with a 1.18-mm (No. 16)sieve. Individual sieve sizes of sand can be purchased to mix withthe remaining sand to meet the required grading. Most sands requireat least the addition of more pan material to meet the requiredgrading.

M-47 (M0470000.896)Page 28 of 738-1-96

28

When directed, minor adjustments in sand grading shall be made toprovide a suitable epoxy mortar. Other fillers or commerciallyavailable sand gradings prepared specifically for epoxy mortars may beused in epoxy mortar on approval by the Contracting Officer.

The sand shall be maintained in a dry area at no less than 60 EFtemperature for 24 hours immediately prior to time of use.

e. Safety. - All work shall be performed in accordance with paragraph1.6 of these specifications. Certain additional safety precautions shallbe employed when using uncured epoxy materials. Skin contact withuncured epoxy shall be avoided. Protective clothing, including rubber orplastic gloves, shall be worn by all persons handling epoxy materials. All exposed skin areas that may come in contact with the material shallbe protected with a protective barrier cream formulated for that purpose. Adequate ventilation shall be provided and maintained at all times duringuse of epoxy and epoxy solvents. Fans used for ventilating shall beexplosion proof. If necessary, respirators that filter organic fumes andmists shall be worn. If spray application is used, the operator shallwear a compressed air-fed hood, and no other personnel shall be closerthan 100 feet if downwind of the operator when spraying is beingperformed. All epoxy-contaminated materials such as wipes, emptycontainers, and waste material shall be continually disposed of incontainers which are protected from spillage. Epoxy spillage shall beimmediately and thoroughly cleaned up. Appropriate solvents may be usedto clean tools and spray guns, but in no case shall the solvents beincorporated in any epoxy resin or in the placing operation. Solventsshall not be used to remove epoxy materials from skin. Only soap, water,and rags shall be used for this purpose.

All tools shall be completely dried after cleaning and before reuse. Allmaterials, tools, and containers contaminated with epoxy resin or epoxycuring agent shall be removed from the site for disposal in accordancewith appropriate local or Federal regulations.

f. Concrete preparation. - Surface preparation and needed removal ofexisting concrete shall be as in section 2, except that the saw cut shallbe 1 inch or equal to the depth of the repair, whichever is less. Forrepairs less than 1 square foot in area, the required vertical edge maybe accomplished with a pneumatic tool or hydrodemolition equipment inlieu of saw cutting. For minor cosmetic repairs of surface defects lessthan 2 inches in diameter, surface preparation may be limited to cleaningwith a small wire brush, removing dust, and heating in depth. Epoxypaste meeting the requirements of ASTM C 881, grade 3, may be usedwithout a bond coat for minor cosmetic repairs of surface defects lessthan 2 inches in diameter in lieu of epoxy-bonded epoxy mortar when allof the conditions for use of epoxy mortar are met. Any overfilling ofminor surface defects shall be removed by grinding after hardening iscomplete. Where repairs are exposed to public view, color matching ofthe repair material to the existing concrete shall be done.

The surfaces of the existing concrete to which epoxy mortar is to beepoxy bonded shall be prepared and maintained in a clean and drycondition. Unless epoxy mortar application to wet concrete surfaces isapproved by the Contracting Officer. The existing concrete shall bepreheated in depth. Preheating shall be sufficient to drive internalmoisture from the repair surface and prevent its return until the bondcoat is in place. Preheating shall not cause damage to or instantsetting of the bond coat.

M-47 (M0470000.896)Page 29 of 738-1-96

g. Application. -

(1) Forms. - Forms shall be used as necessary to prevent slumping orsagging of finished epoxy-bonded epoxy mortar. Such forms shall becovered with polyethylene film, and form oil shall not be used.

(2) Preparation of epoxy resin for bond coat. - The epoxy resin is atwo-component material which requires combination of components andmixing prior to use. Once mixed, the material has a limited pot lifeand must be used immediately. The bonding system shall be prepared byadding the curing component to the resin component in the proportionsrecommended by the manufacturer, followed by thorough mixing. Sincethe working life of the mixture depends on the temperature (longer atlower temperature, much shorter at higher temperature), the quantityto be mixed at one time shall be applied and topped withinapproximately 30 minutes. The addition of thinners or diluents to theresin mixture shall not be done. Both components of class C epoxyshall be stored above 60 EF prior to use.

(3) Application of epoxy resin bond coat for epoxy-bonded epoxymortar. - Immediately after the epoxy resin is mixed, it shall beapplied to the prepared, dry existing concrete at a coverage of notmore than 80 square feet per gallon, depending on surface conditions. The area of coverage per gallon of agent depends on the roughness ofthe surface to be covered and may be considerably less than themaximum specified. The epoxy resin may be applied by any convenient,safe method such as squeegee, brushes, or rollers, which will yield aneffective coverage, except that spraying of the materials will bepermitted only if an efficient airless spray is used and when theconcrete surfaces to receive the agent are 70 EF or warmer, whichspray shall be demonstrated as providing an adequate job with minimumoverspray prior to approval of its use.

Care shall be exercised to confine the epoxy resin to the area beingbonded and to avoid contamination of adjacent surfaces. However, theepoxy bond coat shall extend slightly beyond the edges of the repairarea.

Steel to be embedded in epoxy mortar shall be coated with epoxy resin. The steel shall be prepared in accordance with the requirements ofsection 2 and by removing all loose rust either with a wire brush orby wet sandblasting. The exposed steel shall be completely coatedwith epoxy resin at the time it is being applied to the concretesurfaces of the repair area.

The applied epoxy resin film shall be in a fluid condition at the timethe epoxy mortar is placed. The epoxy resin may be allowed to stiffento a very tacky condition rather than a fluid condition before epoxymortar is placed on steep sloping or vertical surfaces, in which casespecial care shall be taken to thoroughly compact the epoxy mortaragainst the stiffening bond coat. In the event the bond coat iscuring too quickly to meet the placement requirements, a second bondcoat shall be applied over the first while the first bond coat isstill tacky. If any bond coat has cured beyond the tacky state, itshall be completely removed by sandblasting, and proper cleanup,heating, and drying shall be accomplished and a new bond coat applied.

(4) Placing and finishing. - The epoxy mortar shall be composed ofsand and epoxy resin suitably blended to provide a stiff, workablemixture. The epoxy components shall be mixed thoroughly prior to the

M-47 (M0470000.896)Page 30 of 738-1-96

30

application of the bond coat and prior to the addition of the sand. The mixture proportions shall be established, batched, and reported ona weight basis, provided that the dry sand and mixed epoxy may bebatched by volume using suitable measuring containers that have beencalibrated on a weight basis. If equivalent volume proportions arebeing used, care shall be taken to prevent confusing them with weightproportions. Epoxy mortar will require approximately 5-1/2 to 6 partsof graded sand to 1 part epoxy, by weight. The Contracting Officerwill determine, and adjust where necessary, the mix proportions forthe particular epoxy and sand being used. The epoxy mortar shall bethoroughly mixed with a slow-speed mechanical stirrer or otherequipment producing equivalent results. The mortar shall be mixed insmall-sized batches so that each batch will be completely mixed andplaced within approximately 30 minutes from the time the twocomponents for the epoxy resin are combined. The addition of thinnersor diluents to the mortar mixture will not be permitted.

The prepared epoxy mortar shall be tamped, flattened, and smoothedinto place in all areas while the epoxy bond coat is still in a fluidcondition. The mortar shall be worked to grade and given a steeltrowel finish. Special care shall be taken at the edges of the areabeing repaired to ensure complete filling and leveling and to preventthe mortar from being spread over surfaces not having the epoxy bondcoat application. Steel troweling shall be performed in a manner tobest suit the prevailing conditions but, in general, shall beperformed by applying slow, even strokes. Trowels may be heated tofacilitate the finishing. The use of thinner, diluents, water, orother lubricant on placing or finishing tools will not be permitted,except for final cleanup of tools. After leveling of the epoxy mortarto the finished grade where precision surfaces are required, themortar shall be covered with plywood panels smoothly lined withpolyethylene sheeting and weighted with sandbags or otherwise braced,or by other means acceptable to the Contracting Officer, until dangerfrom slumping has passed. When polyethylene sheeting is used, noattempt shall be made to remove it from the epoxy mortar repair beforefinal hardening.

Epoxy-bonded epoxy mortar repairs shall be finished to the plane ofthe surfaces adjoining the repair areas. The final finished surfacesshall match the texture of the surfaces adjoining the repair areas.

h. Curing and protection. - Epoxy-mortar repairs shall be curedimmediately after completion of each repair area at not less than 60 EFuntil the mortar is hard. Post curing shall then be initiated atelevated temperatures by heating, in depth, the epoxy mortar and theconcrete beneath the repair. Post curing shall continue for a minimum of4 hours at a surface temperature not less than 90 EF nor more than 110 EF,or for a minimum of 24 hours at a surface temperature not less than 60 EFnor more than 110 EF. The heat shall be supplied by using portablepropane-fired heaters, infrared heat lamps, or other approved methodscapable of producing the required temperature and positioned so that therequired surface temperatures are obtained.

In no case shall epoxy-bonded epoxy mortar be subjected to moisture untilafter the specified post curing has been completed.

M-47 (M0470000.896)Page 31 of 738-1-96

3.8 EPOXY-BONDED CONCRETE

a. General - Epoxy-bonded concrete is defined as freshly mixed portlandcement concrete that is placed over a fluid epoxy resin bond coat onhardened existing concrete. Epoxy-bonded concrete repair may be usedwhen the depth of repair is 1-1/2 inches or greater.

b. Submittals. -

(1) When directed by the Contracting Officer, the Contractor shallsubmit samples of the epoxy-resin bonding system. The samples shallbe submitted at least 30 days prior to use in the work to the Bureauof Reclamation, Attn D-3731, Building 56, Denver Federal Center, WestSixth Avenue and Kipling Street, Denver CO 80225.

(2) Certification of epoxy-bonding agent. - The Contractor shallfurnish the Contracting Officer the manufacturer's certification ofconformance of the epoxy-resin bonding system with thesespecifications. The certification shall identify the Reclamationsolicitation/ specifications number(s) under which the epoxy is to beused and shall include the quantity represented, the batch numbers ofthe resin and curing agent, and the manufacturer's results of testsperformed on the particular combination of resin and curing agent.


d. Materials. -

(1) Concrete materials. - The materials and procedures used toprepare and mix concrete for epoxy-bonded concrete repair shall be asspecified in subparagraph 3.6.d. except that slump of concrete, whenplaced, shall not exceed 1-1/2 inches.

(2) Epoxy resin. - The epoxy-resin bonding system shall meet therequirements of specification, ASTM C 881 for a type II, grade 2,class B or C epoxy system. In addition, it shall be a 100-percentsolids system and shall not contain unreactive diluents or wettingagents. Volatile solvents shall not be incorporated into the epoxysystem.

e. Safety. - All work shall be performed in accordance with paragraph1.6 and these specifications. Certain additional safety precautionsshall be employed when using uncured epoxy materials. Skin contact withuncured epoxy shall be avoided. Protective clothing, including rubber orplastic gloves, shall be worn by all persons handling epoxy materials. All exposed skin areas that may come in contact with the material shallbe protected with a protective barrier cream formulated for that purpose. Adequate ventilation shall be provided and maintained at all times duringuse of epoxy and epoxy solvents. Fans used for ventilating shall beexplosion proof. If necessary, respirators that filter organic fumes andmists shall be worn. All epoxy-contaminated materials such as wipes,empty containers, and waste material shall be continually disposed of incontainers which are protected from spillage. Epoxy spillage shall beimmediately and thoroughly cleaned up. Appropriate solvents may be usedto clean tools and spray guns, but in no case shall the solvents beincorporated in any epoxy resin or in the placing operation. Solventsshall not be used to remove epoxy materials from skin. Only soap, water,and rags shall be used for this purpose.

M-47 (M0470000.896)Page 32 of 738-1-96

32

All tools shall be completely dried after cleaning and before reuse.

All materials, tools, and containers contaminated with epoxy resin orepoxy curing agent shall be removed from the site for disposal inaccordance with appropriate local or Federal regulations.

f. Concrete preparation. - Concrete to be repaired by epoxy-bondedconcrete shall be prepared in accordance with the provisions of section2, except that the perimeters of the repair shall be saw cut to a minimumdepth of 1 inch. Epoxy-bonded concrete shall not be applied to concretesurfaces at a surface temperature less than 60 EF nor greater than 90 EF.

g. Application of epoxy-bonded concrete. -

(1) Forms. - Forms shall be used for epoxy-bonded concrete whenevernecessary to confine the concrete and shape it to the required lines. The forms shall have sufficient strength to withstand the pressureresulting from placing operations, shall be maintained rigidly inposition, and shall be sufficiently tight to prevent loss of mortarfrom the concrete.

(2) Preparation of epoxy resin. - The epoxy resin is a two-componentmaterial which requires combination of components and mixing prior touse. Once mixed, the material has a limited pot life and must be usedimmediately. The bonding system shall be prepared by adding thecuring component to the resin component in the proportions recommendedby the manufacturer, followed by thorough mixing. Since the workinglife of the mixture depends on the temperature (longer at lowertemperature, much shorter at higher temperature), the quantity to bemixed at one time shall be applied and topped within approximately 30minutes. The addition of thinners or diluents to the resin mixturewill not be permitted. Both components of class C epoxy shall be at60 EF prior to use.

(3) Application of epoxy resin bond coat for surface repairs. - Immediately after the epoxy resin is mixed, it shall be applied to theprepared, dry existing concrete at a coverage of not more than 80square feet per gallon, depending on surface conditions. The area ofcoverage per gallon of agent depends on the roughness of the surfaceto be covered and may be considerably less than the maximum specified. The epoxy resin may be applied by any convenient, safe method such assqueegee, brushes, or rollers, which will yield an effective coverage,except that spraying of the materials will be permitted only if anefficient airless spray is used and when the concrete surfaces toreceive the agent are 70 EF or warmer, which spray shall bedemonstrated as providing an adequate job with minimum overspray priorto approval of its use. If spray application is used, the operatorshall wear a compressed air-fed hood, and no other personnel shall becloser than 100 feet if downwind of the operator when spraying isbeing performed.

Care shall be exercised to confine the epoxy resin to the area beingbonded and to avoid contamination of adjacent surfaces. However, theepoxy bond coat shall extend slightly beyond the edges of the repairarea.

Steel to be embedded in epoxy-bonded concrete shall be coated withepoxy resin. The steel shall be prepared in accordance with therequirements of section 2 and in the same manner required forpreparation of the concrete being repaired. The exposed steel shall

M-47 (M0470000.896)Page 33 of 738-1-96

be completely coated with epoxy resin at the time it is being appliedto the concrete surfaces of the repair area.

The applied epoxy resin film shall be in a fluid condition at the timethe concrete is placed, provided that the epoxy resin may be allowedto stiffen to a very tacky condition rather than a fluid conditionbefore concrete is placed on steep sloping or vertical surfaces, inwhich case special care shall be taken to thoroughly compact theconcrete against the stiffening bond coat. In the event that anapplied film cures beyond the fluid condition, or a very tackycondition where permitted, before the concrete is placed, a secondbond coat shall be applied while the first bond coat is still tacky. If any bond coat has cured beyond the tacky state, it shall becompletely removed by sandblasting, and proper cleanup, heating, anddrying shall be accomplished, and a new bond coat applied.

(4) Placing and finishing. - Use of epoxy-bonded concrete in repairsrequiring forming, such as on steeply sloped or vertical surfaces,will be permitted only when the forming required is such that the bondcoat can be applied and the concrete properly placed within the timeperiod necessary to ensure that the applied bond coat will still befluid, or tacky where permitted.

Immediately after application of the epoxy bond coat, while the epoxyis still fluid, concrete shall be spread evenly to a level slightlyabove grade and compacted thoroughly by vibrating, tamping, or both. Vibrators shall not be permitted to penetrate through the freshconcrete to the level of the fluid epoxy bond coat. Such vibrationcan emulsify the epoxy and reduce the bond. Tampers shall besufficiently heavy for thorough compaction. After being compacted andscreeded, the concrete shall be given a wood float or steel trowelfinish, as directed. Troweling, if required, shall result in asmooth, dense finish that is free from defects and blemishes. As theconcrete continues to harden, the surface shall be given successivetrowelings. The final troweling shall be performed after the surfacehas hardened to such an extent that no cement paste will adhere to theedge of the trowel. The number of trowelings and time at whichtrowelings are performed shall be subject to approval of theContracting Officer.

The surfaces of epoxy-bonded concrete repairs shall be finished to theplane of the surfaces adjoining the repair areas. The final finishedsurfaces shall match the texture of the surfaces adjoining the repairareas.

h. Curing and protection. - The Contractor shall cure and protect allrepairs from damage until acceptance by the Government. Concrete shallbe protected against freezing for not less than 6 days from time ofplacement.

As soon as the epoxy-bonded concrete has hardened sufficiently to preventdamage, the surface shall be moistened by spraying lightly with water andthen covering with sheet polyethylene, or by applying an approved curingcompound, provided that curing compound shall be used for curing concretewhenever there is any possibility that freezing temperatures will prevailduring the curing period. Sheet polyethylene, if used, shall be anairtight, nonstaining, waterproof covering which will effectively preventloss of moisture from the concrete by evaporation. Edges of thepolyethylene shall be lapped and sealed. The waterproof covering shallbe left in place for not less than 14 days.

M-47 (M0470000.896)Page 34 of 738-1-96

34

If a waterproof covering is used and the concrete is to be subjected toany use that might rupture or otherwise damage the covering during thecuring period, the covering shall be protected by a suitable layer ofclean wet sand or other cushioning material that will not stain concrete,as approved by the Contracting Officer. Application of curing compound,if used, shall be in accordance with Reclamation's "Specifications forConcrete Curing Compound, M-30." After the curing has been accomplished,the covering, except curing compound if used, and all foreign materialshall be removed and disposed of as directed.

3.9 POLYMER CONCRETE SYSTEMS a. General. - Polymer concrete repair systems for concrete may be eitherof two types: a methacrylate monomer system, or a vinyl ester resinsystem. These materials may be used for patches, overlays, grout pads,and embedment of sills, gates, and similar structures in concretemembers. Prior approval of the Contracting Officer is required forapplications where the repair is exposed to the direct rays of the sun orsubjected to rapid temperature changes in excess of 10 EF per hour formore than a 3-hour period. The materials may be supplied as aprepackaged system or as components for a system designed for use aspolymer concrete.

The polymer concrete system shall consist of a 100-percent reactivemonomer or resin system (no nonreactive diluents or solvents arepermitted); an initiator for polymerization of the resin or monomersystem, a promoter to activate the initiator; aggregate; and a primersystem to be applied to the surface of the concrete to be repaired. Thesystem shall be supplied with or without pigments to approximate thecolor of concrete, as directed by the Contracting Officer.

b. Submittals. - Before starting work, the Contractor shall submit tothe Contracting Officer for approval the following documents:

(1) A safety plan.

(2) A statement of technical qualifications, training, and pastexperience in handling and applying polymer concrete materials.

(3) A manufacturer's affidavit that states the chemical constituentsand proportions of the material, a Materials Data Safety Sheet foreach component, the use for which the material is designed,instructions on storage and use of the materials, and typicalmechanical and physical properties of the final product.


d. Materials. -

(1) Monomer and resin systems. -

(a) Methacrylate monomer systems. - The monomer system may bebased on either methyl methacrylate monomer or on high molecularweight methacrylate monomer systems. The monomer system shallconsist of 100-percent reactive components, and no nonreactivediluents or solvents shall be permitted. The initiator shall bean organic peroxide. The promoter shall be either a cobalt salt oran organic amine compound. Materials shall be used in theproportions recommended by the manufacturer for the temperature

M-47 (M0470000.896)Page 35 of 738-1-96

conditions at the job site to meet the pot life and curing timerequirements of these specifications.

(b) Vinyl ester resin systems. - The vinyl ester resin shall be anelastomer-modified dimethacrylate diglycidyl ether of bisphenol Aand shall be Dow Chemical Company Derakane 8084; or equal havingthe following salient characteristics:

Liquid Resin Properties Styrene content 45 percent by weight Viscosity, Brookfield (cps), 77 EF 1,200 Flash point, cc, (EF) 82

Clear Casting Properties Tensile strength, (lb/in2) 10,000 Tensile modulus (lb/in2) 430,000 Elongation, percent 10 Flexural strength, (lb/in2) 16,000 Flexural modulus, (lb/in2) 420,000 Heat distortion temperature (EF) 170

The initiator shall be an organic peroxide and the promoter shallbe cobalt napthenate or cobalt octoate. Materials shall be used inthe proportions recommended by the manufacturer for the temperatureconditions at the job site to meet the pot life and curing timerequirements of these specifications.

(2) Aggregates. -

(a) Prepackaged systems. - Prepackaged systems normally contain apreblended fine aggregate. The use of additional fine aggregateshall not be permitted in these systems unless specificallyauthorized by the manufacturer. Prepackaged systems that do notcontain a preblended fine aggregate shall use a fine aggregatemeeting the requirements of subparagraph 3.9.d.(2)(b). Prepackagedpolymer concrete systems may be extended by the addition of coarseaggregate. The maximum size of the coarse aggregate shall notexceed the lesser of either one-third of the depth of the repair or1-1/2 inches. The coarse aggregate shall be composed of hard,dense, clean durable, well-graded rock particles.

(b) Separate component polymer concrete systems. - The aggregateshall be composed of hard, dense, clean, durable, well-graded rockparticles. Not more than 2 percent by weight of the fine aggregateshall pass the 75 µm (No. 200) sieve, and the maximum aggregatesize shall not be greater than one-third the depth of the repair. The grading shall be based on the following guide:

Nominal size Aggregate grading fraction percent retained by weight 9.5 - 19.0 mm -- -- -- -- -- 29 (3/8 - 3/4 inch)

4.75 - 9.5 mm -- -- -- -- 29 20 (No. 4 - 3/8 inch)

2.36 - 4.75 mm -- -- -- 29 21 16 (No. 8 - No. 4)

M-47 (M0470000.896)Page 36 of 738-1-96

36

1.18 - 2.36 mm -- -- 31 21 16 10 (No. 16 - No. 8) 600 µm - 1.18 mm -- 31 22 15 10 7 (No. 30 - No. 16)

300 - 600 µm 50 23 16 10 7 5 (No. 50 - No. 30)

150 - 300 µm 30 16 10 8 4 (No. 100 - No. 50)

*Pan 20 30 21 17 13 9 *NOTE: Pan material shall consist of: 1. Minus 75 µm (No. 200) sieve size ground silica, or

2. Minus 75 µm (No. 200) sieve size crushed hard, dense, durable,clean rock washed free of clay and organic impurities, or 3. A mixture of 1 or 2 above with 50% fly ash.

(3) Coupling agent. - The coupling agent incorporated into themonomer or resin system shall be an organosilane compound, UnionCarbide A-174, or equal.

(4) Primer. - The polymer concrete shall be applied to a prepared andprimed concrete surface. The primer shall consist of either a methylmethacrylate monomer system, a high molecular weight methacrylatemonomer system, or an elastomer-modified vinyl ester resin system(Dow Chemical Company Derakane 8084, or equal). The same monomer orresin system used in the polymer concrete is acceptable as a primer. The polymer concrete shall be applied to a primed surface while theprimer is still tacky and has not completely cured to a hard and dryfinish, with the exception of methyl methacrylate polymer concretesystems applied to a methyl methacrylate primer system which does notcontain cross-linking comonomers which may be applied to a cured anddry primed surface. The primer system shall be formulated accordingto the manufacturer's instructions to give adequate pot life for thejob site temperature conditions for proper application of the polymerconcrete.

(5) Polymer concrete properties. - The polymer concrete shall havethe following properties:

(a) Curing time of 1 to 3 hours at ambient temperature (substrateand air) of 32 to 100 EF.

(b) Pot life of 15 to 30 minutes at ambient temperatures of 32 to100 EF.

M-47 (M0470000.896)Page 37 of 738-1-96

(c) Compressive strength of at least 7,000 lb/in2. (ASTM C 39).

(d) Splitting tensile strength of at least 1,000 lb/in2. (ASTMC 496).

(e) Linear shrinkage, less than 0.05%.

(f) Bond strength to concrete - at least equal to the splittingtensile strength of the base concrete.

e. Safety. - All work shall be performed in accordance with requirementsof paragraph 1.6 and these specifications. The Contractor shall also:

(1) Hold a safety meeting at the job site conducted by an industrialhygienist or by a technically qualified professional staff member toacquaint and instruct all workers and supervisors on the job in theproper care and handling of the polymer concrete materials asspecified by the manufacturer of the polymer concrete, safetyprecautions to be observed, personal protective gear, and protectionof the environment.

(2) Require all workers, supervisors, inspectors, visitors, and otherpeople at the job site to wear personal protective gear as directed bythe Contracting Officer.

(3) Ensure that the polymer concrete materials are stored, handled,and applied in the manner specified by the manufacturer. In addition:

(a) Storage. - polymer concrete materials shall be stored in theshipping containers in a well-ventilated area and out of the directrays of the sun. The storage temperature shall not exceed 80 EF (27 EC). Materials shall not be stored longer than 3 months.

(b) Mixing and application. - No smoking, flame, or other ignitionsources shall be permitted during mixing and application. Type Bor type ABC fire extinguishers shall be provided at the mixing andapplication sites. Electrical equipment in contact with thepolymer concrete should be grounded for safe discharge of staticelectricity. (c) Handling. - Workers shall be provided and required to wearrubber boots, disposable protective clothing, splash-type safetygoggles, rubber gloves, and organic vapor respirators as directedby the Contracting Officer. A heated eye wash capable ofsustaining a 15-minute stream of clean, room temperature watershall be provided at the mixer and at the application site. Materials coming into direct contact with the skin shall beimmediately removed using soap and water.

(4) Prevent the contamination of soil or water at the job site byliquid components.

(5) Dispose of liquid components and excess materials at the job siteby combining the materials in the same manner and procedure used formixing polymer concrete, placing the mixed materials in an opencontainer, and allowing the material to harden. Hardened polymerconcrete is nonpolluting and may be disposed of as a solidnonhazardous waste.

f. Concrete preparation. - In addition to the requirements of section 2,the concrete surface shall be dry and primed with an approved primer.

M-47 (M0470000.896)Page 38 of 738-1-96

38

The primer and the polymer concrete shall not be applied until thesurface preparation meets the approval of the Contracting Officer. Thedryness of the surface shall be determined by taping a sheet oftransparent polyethylene sheeting to the surface and exposing it to thefull rays of the sun for at least 4 hours and observing the interiorsurface of the polyethylene sheeting for the occurrence of condensedmoisture. As an alternative method, a calibrated moisture meter whichmeets the approval of the Contracting Officer may be used to determinethe dryness of the surface.

g. Preparation and application requirements. -

(1) Initiator and promoter. - The initiator and promoter shall beprebatched and packaged separately from each other in a manner so thatthe two components cannot be combined until the time of the concretemixing operation. The promoter shall be combined with the monomer orresin system prior to the addition of the initiator. UNDER NOCIRCUMSTANCES SHALL THE INITIATOR BE ADDED TO OR DIRECTLY CONTACT THEPROMOTER. THE DIRECT COMBINATION OF PROMOTER AND INITIATOR WILLRESULT IN AN EXTREMELY VIOLENT AND EXPLOSIVE REACTION.

(2) Sequence of addition and combination of materials at the mixer. -The polymer concrete materials shall be combined in the sequence andmanner specified by the manufacturer.

(3) Mixing of polymer concrete. - The polymer concrete shall be mixedin a paddle-type power mixer, a rotating drum-type power mixer, orother type of power equipment approved by the Contracting Officer. Polymer concrete materials shall be mixed according to therecommendations of the manufacturer of the polymer concrete materialsfor at least 3 minutes.

(4) Removal of polymer concrete from the mixer. - The polymerconcrete shall be removed from the mixer immediately after mixing.

(5) Appropriate forms shall be used for polymer concrete whenevernecessary to confine the polymer concrete and shape it to requiredlines. The surfaces of the forms shall be coated with a release agentthat will effectively prevent sticking without damage to the polymerconcrete surfaces.

3.10 THIN POLYMER CONCRETE OVERLAY

a. General. - Thin polymer concrete overlay shall consist of one coat ofprimer and one or more coats of sealant as directed by the ContractingOfficer.

The coat of primer shall consist of vinyl ester resin, initiator, andpromoter. Each coat of sealant shall consist of the same materials as inthe primer, but with the addition of silica filler, titanium dioxidepigment, and carbon black pigment.

b. Submittals. - The Contractor shall, before starting work, provide amanufacturer's affidavit which indicates the chemical constituents of thematerial by proportion. The chemical constituents shall correspond tothe requirement of subparagraph 3.10.d.

c. Quality assurance. - Quality assurance shall be in accordance withparagraph 1.4 and these specifications.

M-47 (M0470000.896)Page 39 of 738-1-96

The vinyl ester resin shall be stored in the shipping containers and keptin the shade, well ventilated, and out of direct sunlight. Therecommended storage temperature is 50 to 75 EF. Resin shall not reach 80EF or higher, as it will start to gel. The resin has a storage life ofabout 3 months. During storage, the resin shall not come in contact withcopper, brass, zinc, or rust, as discoloration, polymerization, orinterference with normal cure conditions can occur. Resin shall also notcontact rubber, as resin is a solvent for rubber.

Styrene monomer, which is a component of vinyl ester resin, is flammableand forms explosive mixtures in the air; however, it is not sufficientlyflammable to be listed as a "flammable liquid" under Interstate CommerceCommission definitions (flash point at or below 80 EF). The explosivelimits are 1.1 to 6.1 percent volume in air.

The Contracting Officer will not allow the use of vinyl ester resin if ithas already polymerized, gelled, discolored, or will not cure undernormal conditions. Substandard materials shall be replaced at theexpense of the Contractor.

d. Materials. -

(1) Vinyl ester. - The vinyl ester resin material shall be DowDerakane 8084 elastomer-modified vinyl ester resin, manufactured byDow Chemical Co., 2800 Mitchell Drive, Walnut Creek CA 94596; orequal. It shall meet the requirements of 3.9.d.(1)(b).

(2) Initiator. - The initiator shall be cuemene hydroperoxide - 78percent as manufactured by: Lucidol Division, Penwalt Corp., 1740Military Road, Buffalo NY 14240; Reichold Chemicals, Inc., 107 SouthMotor Avenue, Azusa CA 91706; Witco Chemicals, U.S. PeroxygenDivision, 850 Morton Avenue, Richmond CA 94804; or equal.

(3) Promoter. - The promoter shall be cobalt napthenate; 6 percent.

(4) Filler. - The filler shall be ground silica, minus 45 µm(No. 355) sieve size as manufactured by: Ottawa Silica Co., Ottawa,Illinois; VWR Scientific (Silco Seal 395 Ground Silica), PO Box 3200,San Francisco CA 94119; or equal.

(5) Pigment for opaqueness. - Two pigments shall be used and theyshall be:

(a) Titanium dioxide powder as manufactured by: VWR Scientific, POBox 3200, San Francisco CA 94119; MCB Manufacturing Chemist, Inc.,470 Valley Drive, Brisband CA 94005; or equal.

(b) Carbon lamp black or bone black powder. - (Do not useactivated carbon)

e. Safety. - All work shall be performed in accordance with paragraph1.6 and these specifications. No smoking, flame, or other ignitionsource shall be present during mixing and the application procedures. Fire extinguishers (types B or ABC) shall be provided. Equipmentcontacting resins shall be grounded for safe discharge of staticelectricity. Tools used shall be the non-sparking, special alloy type.

Workers shall be provided with rubber boots, rubber gloves, protectiveclothing, safety goggles or face shields, and organic vapor respirators. It is important to avoid inhalation of vapors and direct eye or skin

M-47 (M0470000.896)Page 40 of 738-1-96

40

contact. Eyewash facility shall be available which will provide a clean,room temperature flushing stream for a minimum of 15 minutes. Contaminated clothing shall be discarded immediately. Proper tools andfacilities to quickly remove spills shall be at the worksite.

Personnel shall follow manufacturer's recommendations for safe handlingof vinyl ester resin and all additives.

CUEMENE HYDROPEROXIDE INITIATOR SHALL NEVER BE ADDED DIRECTLY TO COBALTNAPTHENATE PROMOTER OR AN EXTREMELY VIOLENT AND EXPLOSIVE REACTION WILLOCCUR.

f. Concrete preparation. - Concrete surfaces designated to receive thethin polymer concrete overlay shall be prepared in accordance with section 2. The minimum preparation shall consist of wet sandblasting orwater blasting the concrete to a clean, sound surface condition followedby drying.

g. Application of the thin polymer concrete overlay. -

(1) Coverage. - An average coverage rate of 50 to 75 square feet pergallon of applied material per coat over the entire surface isanticipated for this work. The surface texture of the concrete mayaffect this coverage rate.

(2) Mixing proportion. -

(a) Primer: 5.0 gallons vinyl ester resin 0.60 pound initiator

0.25 pound promoter

(b) Sealant: 5.0 gallons vinyl ester resin 1.35 pounds initiator 0.27 pounds promoter 40.0 pounds filler 4.0 pounds titanium dioxide pigment 0.02 pound carbon lamp black pigment

(3) Variations. - The proportions of cobalt napthenate promoter andcuemene hydroperoxide initiator were selected to give a 2- to 4-hourpot life at a temperature of about 70 EF. The rate of thepolymerization reaction also depends on temperature - in colderweather the reaction will be slower, and in hot weather or insunshine, the reaction will proceed faster. The temperature effectscan be compensated for, to a certain extent, by increasing the totalamount of initiator plus promoter in cold weather and decreasing theamount in hot weather.

Great care shall be exercised in proportioning the titanium dioxide and the carbon black to ensure exact color between batches of sealantlayer.

The Contracting Officer may require variations from the proportionsand quantities specified above and trial mixtures.

At no additional cost to the Government the Contracting Officer mayrequire two trial mixtures utilizing a total of 5 gallons of vinylester resin with a proportional amount of other materials as indicatedin subparagraph 3.10.g.(2). The Contractor shall supply, mix, andapply the trial polymer overlay where directed and in a manner as

M-47 (M0470000.896)Page 41 of 738-1-96

indicated by these specifications. The Contracting Officer shall begiven 12 hours' notice before a trial mix is applied.

(4) Mixing. - The filler, pigments, and cobalt napthenate promotershall be mixed with vinyl ester resin in a paddle-type or rotatingdrum power mixer in advance of the application. Mixtures shall beprepared in maximum volumes of 5 gallons of resin per mixed batch.

The Contractor shall mix the required constituents, with the exceptionof the cuemene hydroperoxide, to the satisfaction of the ContractingOfficer. The sealant material will then be required to set for 45 to90 minutes for the filler and pigment to become thoroughly wetted bythe vinyl ester resin. Just prior to use, the cuemene hydroperoxideinitiator shall then be added and the sealant mixture mixed again tothe Contracting Officer's satisfaction. CUEMENE HYDROPEROXIDEINITIATOR AND COBALT NAPTHENATE PROMOTOR SHALL NEVER BE ADDED TOGETHERDIRECTLY, OR AN INSTANTANEOUS AND VIOLENTLY EXPLOSIVE REACTION COULDOCCUR. For the primer, the setting period may be omitted, but theinitiator must still be added after the first mixing of the promoter,then mixed again.

(5) Application. - The primer shall uniformly and completely coverthe surface by being spread and scrubbed into the concrete surfacewith a paint roller, brush, or push broom. Discontinuities andpuddles shall be eliminated by vigorous scrubbing action. Theapplication rate of primer is expected to be 1 gallon per 50 to 75square feet of surface area, but may vary due to texture of theprepared surface.

The pigmented sealant layers of the overlay material shall be appliednot less than 4 and no greater than 24 hours after the application ofthe primer or succeeding sealant layer. The primer layer may not havecompletely cured during this time period. The sealant shall beapplied to dry, primed surfaces, and provisions shall be taken toprevent wetting of the surfaces from rain or leakage and seepage ofwater. The sealant layers shall also be applied with a paint roller,brush, or push broom. The application rate of the sealant is expectedto be 1 gallon per 50 to 75 square feet of surface area.

The primer and sealant layers shall be spread evenly and uniformlyover the surface.

3.11 RESIN INJECTION

a. General. - When hardened concrete is cracked in depth or when hollowplane delaminations or open joints exist in hardened concrete and whenstructural integrity or watertightness must be restored for the structureto be serviceable, resin injection shall be used for repair, as directed.

However, since not all cracked, delaminated, or jointed concrete can berestored to serviceable condition by resin injection, resin injectionrepairs shall be made only as directed by the Contracting Officer.

Two basic types of injection resin are used to repair concrete:

(1) Epoxy resins are used to rebond cracked concrete and to restorestructural soundness. Epoxy resins may also be used to eliminatewater leakage from concrete cracks or joints, provided that cracks tobe injected with epoxy resin are stationary. Cracks that are activelyleaking water and that cannot be protected from uncontrolled water

M-47 (M0470000.896)Page 42 of 738-1-96

42

inflow shall not be injected with epoxy resin. Cracks to be injectedwith epoxy resin shall be between 0.005 inch and 0.25 inch in width.

(2) Hydrophilic polyurethane resin is used to eliminate or reducewater leakage from concrete cracks and joints and can be used toinject cracks subject to some degree of movement. Hydrophilicpolyurethane resin shall not be used to inject concrete cracks orjoints when restoration of structural bond is desired. Cracks to beinjected with polyurethane resin shall be 0.005 inch in width orgreater.

Other types of injection resin are available for nonstandard orspecialized repair applications. Use of these materials shall requirespecific approval of the Contracting Officer.

b. Submittals. - The Contractor shall provide the Contracting Officerwith evidence that the Contractor is qualified to perform resin injectionrepairs. The data shall show that the Contractor has a minimum of 3years of experience in performing resin injection work similar to thatdetailed in the drawings and specifications.

The Contractor shall submit a list of 5 projects in which resin injectionwas successfully completed. The list shall contain the followinginformation for each project:

(1) Project name and location.

(2) Owner of project.

(3) Brief description of work.

(4) Date of completion of resin injection work.

If the repair work is performed by the Contractor's personnel under thesupervision of the manufacturer's representative, the data shall showthat the resin manufacturer has a minimum of 5 years' experienceproviding resin materials similar to those specified.

Manufacturer's brochures, technical data sheets, Material Safety DataSheets, and any other information describing the polyurethane resin, theproper formulation to achieve the required tensile strength, bondstrength, and elongation of the cured resin mixture, and recommendedinjection procedures shall be submitted to the Contracting Officer forapproval at least 30 days prior to commencement of crack repairingoperations.

The Contractor shall furnish the Contracting Officer a manufacturer'scertification of conformance of the epoxy or polyurethane resin systemwith these specifications. The certification shall identify theReclamation solicitation/specifications number(s) under which the resinis to be used and shall include the quantity represented, the batchnumbers of the resin, and the manufacturer's results of tests performedon the resin system.

The Contractor shall submit a detailed proposal for epoxy injectionrepair to the Contracting Officer for approval. The approval will bebased on the degree of conformance of the proposal with procedurescontained in Reclamation's Concrete Manual, chapter 7, Eighth Edition,revised reprint, and the report of ACI Committee 503, section 7.2.5, "Useof Epoxy Compounds with Concrete."

M-47 (M0470000.896)Page 43 of 738-1-96

The Contractor shall submit a detailed proposal for polyurethane resininjection repair to the Contracting Officer for approval. The approvalwill be based on the degree of conformance to the basic steps ofpolyurethane resin injection and on the Contracting Officer's judgment ofthe technical feasibility of the Contractor's proposal.

c. Quality assurance. - Quality assurance shall be in accordance withparagraph 1.4 and these specifications. The repair work may be performedby the Contractor or by the Contractor's personnel under the supervisionof the resin manufacturer's representative. If the Contractor performsthe repair work, the Contractor shall provide a full-time, onsitesupervisor throughout the duration of the resin injection work.

If the repair work is performed by the Contractor's personnel under thesupervision of the resin manufacturer's representative the Contractorshall have the resin manufacturer provide a representative who will trainthe Contractor's personnel on the proper techniques of injecting resinwith an injection system approved by the manufacturer. Also, theContractor shall provide a full-time, onsite, manufacturer-certifiedinjection supervisor throughout the duration of the resin injection work.

d. Materials. -

(1) Epoxy resin. - Epoxy resin for injection shall meet therequirements of specification ASTM C-881 for a type I, grade 1 epoxysystem. The class of the system shall be appropriate for thetemperature of the application.

(2) Polyurethane resin. - The polyurethane resin system for injectioninto cracked concrete shall be a two-part system composed of 100percent hydrophilic polyurethane resin and water. The polyurethaneresin, when mixed with water, shall be capable of forming either aflexible closed-cell foam or a cured gel dependent upon the water-to-resin mixing ratio. The amount of water mixed with the polyurethaneresin shall be such that the cured material meets the followingphysical properties:

(a) Minimum tensile strength -- 20 pounds per square inch.

(b) Bond to concrete (wet) -- greater than 20 pounds per squareinch.

(c) Minimum elongation -- 400 percent.

The injection of pure polyurethane resin, not mixed with water, shall not be allowed.

e. Safety. - All work shall be performed in accordance with paragraph1.6 and these specifications.

(1) Epoxy resins. - Certain additional safety precautions shall beemployed when using uncured epoxy materials. Skin contact withuncured epoxy shall be avoided. Protective clothing, including rubberor plastic gloves, shall be worn by all persons handling epoxymaterials. All exposed skin areas that may come in contact with thematerial shall be protected with a protective barrier cream formulatedfor that purpose. Adequate ventilation shall be provided andmaintained at all times during use of epoxy and epoxy solvents. Fansused for ventilating shall be explosion proof. If necessary,respirators that filter organic fumes and mists shall be worn. All

M-47 (M0470000.896)Page 44 of 738-1-96

44

epoxy-contaminated materials such as wipes, empty containers, andwaste material shall be continually disposed of in containers whichare protected from spillage. Epoxy spillage shall be immediately andthoroughly cleaned up. Appropriate solvents may be used to cleantools and spray guns, but in no case shall the solvents beincorporated in any epoxy resin or in the placing operation. Solventsshall not be used to remove epoxy materials from skin. Only soap,water, and rags shall be used for this purpose.

All tools shall be completely dried after cleaning and before reuse.

(2) Polyurethane resins. - Polyurethane injection resin systemscontain either toluene diisocyanate or methylene dephenyldiisocyanate. Both isocyanates can create risks if safe handlingprocedures are not followed. The principal hazards arise fromisocyanate vapor, which will irritate the membranes of the nose,throat, lungs, and eyes. Adequate ventilation is required to preventvapor concentrations from approaching the Threshold Limit Value (TLV). Protective clothing, including rubber or plastic gloves and protectiveglasses, shall be worn by all persons handling polyurethane resins. If necessary, respirators that filter isocyanate vapors and mistsshall also be worn. Monomeric urethane resins react with water toproduce polyurethane and carbon dioxide gas. If this reaction occursinside a closed container, excessive pressures can develop that mayrupture the container. Care must be taken to prevent contamination ofmonomeric urethane resin with water.

Polyurethane resin spillage shall be immediately and thoroughlycleaned up. Spilled polyurethane resin can be absorbed in sand andremoved for burial.

(3) Cleanup and disposal of injection resin. - All materials, tools,and containers contaminated with injection resin, surface sealers, orother contaminants shall be removed from the site for disposal inaccordance with appropriate local or Federal regulations.

f. Concrete preparation. - The concrete surface to be repaired by resininjection shall be thoroughly cleaned of all deteriorated concrete,efflorescence, and all other loose material. The area to be injectedshall then be thoroughly inspected and an injection port drilling andpumping pattern established.

Upon completion of resin injection, all excess material shall be removedfrom the exterior surfaces of the concrete. The final finished surfacesshall match the texture of the surfaces adjoining the repair areas.

g. Application of resin injection repairs to concrete. -

(1) Epoxy resin injection repair. - The process used for epoxyinjection shall fill the entire crack or hollow plane delaminationwith liquid epoxy resin system and shall contain the resin system inthe crack until it has hardened. The Contractor shall be responsiblefor drilling and removing three, a minimum of 2-inch-diameter coresfrom the injected concrete at locations determined by the ContractingOfficer to determine the completeness of the injection repair. Injection shall be considered complete if more than 90 percent of thevoid is filled with hardened epoxy. If injection is not complete,reinjection and additional cores may be required at the direction ofthe Contracting Officer at no additional cost to the Government.

M-47 (M0470000.896)Page 45 of 738-1-96

Epoxy injection repair methods shall be in accordance with theapproved detailed proposal for epoxy injection repair and shall beadjusted to fit the repair situations encountered.

(2) Hydrophilic polyurethane resin injection repairs. - The processused for polyurethane injection of cracks or joints to reduce waterleakage shall consist of the following basic steps:

(a) Intercept the water flow paths with valved drains installedinto the concrete to control the leakage.

(b) Install injection ports by drilling holes designed tointersect the cracks at depth below the concrete surface. Themaximum spacing of injection ports shall not exceed 60 inches, andcloser spacing of ports may be required.

(c) All injection holes shall be flushed with clean water toremove drilling dust and loose debris and to

clean the intersected crack line. Eachdrill hole shall be water tested at theresin injection pressure to determine ifthe crack intersection is open. Polyurethane resin shall not be pumpedinto a drill hole that refuses to takewater at the resin injection pressure.

(d) Inject polyurethane resin system into cracks or joints at the minimum pressure required to obtain the desired travel, filling,and sealing. The mix water to resin ratio shall be 1:1 unlessotherwise approved by the Contracting Officer. The Contractorshould anticipate the necessity to provide a surface seal for thecrack or joint to contain the injection resin. It may also benecessary to inject the crack or joint in an intermittent manner toachieve filling and sealing. Injection shall be by the method ofsplit spacing unless otherwise approved by the Contracting Officer. Primary holes shall be drilled and injected on centers notexceeding 10 feet. Secondary holes, half way between the primaryholes, will then be drilled and injected. If resin take occurs inthe secondary holes, a series of tertiary holes, half way betweenthe secondary and primary holes, shall then be drilled andinjected. All holes shall be injected to absolute refusal.

(e) Remove drains, injection ports, and excess polyurethane uponcompletion of resin cure.

This process shall entirely stop the water leakage to a dust drycondition or as directed by the Contracting Officer.

The pump used to inject the polyurethane resin system shall be atwo-component positive-displacement-type pump with static mixinghead and pressure regulation necessary to control injectionpressures while pumping low volumes. The equipment will besubject to approval by the Contracting Officer. The use of singlecomponent pumps and/or the injection of pure water followed byinjection of pure resin will not be approved.

Polyurethane resin injection methods shall be in accordance with theapproved, detailed proposal for injection repair and shall be adjustedto fit the repair situations encountered.

M-47 (M0470000.896)Page 46 of 738-1-96

46

3.12 HIGH MOLUCULAR WEIGHT METHACRYLIC SEALING COMPOUND

a. General. - A concrete sealing compound is defined as a liquid that isapplied to the surface of hardened concrete to prevent or decrease thepenetration of liquid or gaseous media, such as water, aggressivesolutions, and carbon dioxide, during the service exposure, preferablyafter initial drying to facilitate its absorption into voids and cracks.

The sealing of concrete surfaces with a high molecular weight methacrylicmonomer-catalyst system and sand shall be in accordance with thesespecifications. Other types of concrete sealing compounds may be used bythe Contractor only when approved by the Contracting Officer.

The high molecular weight methacrylic sealing compound shall not be usedto seal concrete subject to frequent or permanent immersion in water; norshall it be used on concrete surfaces exposed to high abrasion forces.

b. Submittals. - The Contractor shall provide the Contracting Officer atable showing preparation of initiator and promoter to be added to themonomer to achieve the cure time requirements based on concrete surfacetemperature. The temperature of the surface to be treated shall rangefrom 45 to 100 EF. If it is desired to work outside these temperatureranges, approval of the Contracting Officer is required, and the monomermanufacturer should be consulted for technical advice.

A MSDS shall be furnished to the Contracting Officer prior to shipment ofmaterial with information pertaining to the safe practices for storage,handling and disposal of the materials and their explosive and flammablecharacteristics, health hazards, and the manufacturer's recommended firefighting techniques. The MSDS shall be posted at all storage areas andat the job site.

The Contractor shall furnish, for approval, a detailed writtendescription of the methods the Contractor plans to use for clean up ofall spills and residue in open containers. See subparagraph 3.12.g.(4).


d. Materials. -

(1) High molecular weight methacrylic monomer. - The monomer shall bea high molecular weight or substituted methacrylate that conforms tothe following properties:

(a) Vapor pressure Less than 1.0 mm HG @ 77 EF (ASTM D 323)

(b) Flash point Greater than 200 EF (Pensky-Martens CC)

(c) Density Greater than 8.4 lb/gal at 77 EF (ASTM D2849)

(d) Viscosity 12 ± 4 cps (Brookfield No. 1 Spindle 60 rpm,at

73 EF)

(e) Index ofrefraction 1.470 ± 0.002

(f) Boiling point @ 1 mm Hg, degrees F 158

M-47 (M0470000.896)Page 47 of 738-1-96

(g) Shrinkage on cure -less than- 11%

(h) Glass transition temperature (DSC), degrees F. 135 EF (ASTMD 3418)

(i) Curing time (100 g mass) Greater than 40 minutes at 77 EF,with 4% cuemene hydroperoxide (ASTM D 2471)

(j) Bond strength greater than 1,500 lb/in2 (ASTM C 882)

(k) No unreactive solvents or diluents shall be permitted in themonomer system.

(2) Initiator-promoter system. -

(a) Initiator Cuemene hydro peroxide - 78 percent

(b) Promoter Cobalt Napthenate - 6 percent

The initiator/promoter system shall be capable of providing a surfacecure time of not less than 40 minutes nor more than 3 hours at thesurface temperature of the concrete during application. Theinitiator/promoter system shall be such that the gel time may beadjusted to compensate for changes in temperature that may occurthroughout the treatment application.

(3) Sand. - The sand shall be clean, dry, and free of organicmaterials, silt, and clay. Except as otherwise approved by theContracting Officer, the sand shall conform to the following grading:

U.S. standard sieve size Percent passing

4.75 mm (No. 4) 1002.36 mm (No. 8) 90-10850 µm (No. 20) 5-10300 µm (No. 50) 0-10

This grading is intended to allow the use of commercially availablesilica sands of No. 8/20 or No. 10/20.

e. Safety. - All work shall be performed in accordance with therequirements of paragraph 1.6 and these specifications. The materialsshall be stored, handled, and applied in accordance with themanufacturer's recommendations. Storage of all materials shall be in theoriginal shipping containers and as specified in this paragraph.

INITIATORS AND PROMOTERS SHALL BE STORED SEPARATELY SINCE COMBINATION CANRESULT IN A VIOLENT REACTION OR EXPLOSION.

Personnel exposed to monomer, initiator, or promoter, or their vaporsshall use minimum protective equipment as follows: safety eye glasses,impervious gloves and aprons, and rubber boots as required. Asdetermined by the Contracting Officer, personnel may be required to usefull-face protective shields, self-contained respiratory equipment, orboth. All personnel handling the monomer or catalysts shall bethoroughly trained in their safe use in accordance with themanufacturer's recommendations.

Unsafe handling practices will be sufficient cause to discontinue workuntil the hazardous procedures are corrected. The handling and use of

M-47 (M0470000.896)Page 48 of 738-1-96

48

the monomer and catalysts shall in all cases comply with the requirementsof applicable Federal, State, and local safety requirements andordinances.

The Contractor shall provide an eye wash and water washing facility foruse in the event of accidental splashing of the monomer or catalysts onthe workers. Eyewash facility shall be capable of providing a clean,room temperature flushing stream for a minimum of 15 minutes. Allsources of sparks or flame must be removed from areas used for storageand handling. In these areas storage and mixing vessels shall beprovided with electrical grounds to prevent static sparks.

Mixing and transfer equipment shall be explosion proof, and sufficientventilation shall be provided to prevent the formation of explosivesealant/air mixtures. In accordance with applicable safety regulations,warning signs, such as "No Smoking" signs, shall be posted. In publicareas, care shall be taken to eliminate sources of sparks or flame whenthe monomer system is present. Particular attention should be given toremoval of welding operations, posting of "No Smoking" signs, and totraffic control to eliminate accidental fires from these sources. Visitors at the job site should be warned of the potential hazards andprovided with applicable safety equipment. The Contractor shall alsoplace an adequate number of 4-A:60B:C fire extinguishers on the job, sothat no portion of the monomer system application is conducted fartherthan 100 feet from the nearest fire extinguisher.

f. Concrete preparation. - The concrete surfaces to be treated shall beclean, dry, and physically sound. All deteriorated concrete shall beremoved in accordance with paragraph 2.1 to obtain a physically soundsurface for treatment. The Contractor shall perform all work required tobring the surfaces to this condition.

Concrete surfaces shall then be prepared by power sweeping and by blowingwith high-pressure air to remove all dirt and foreign material from thesurface and from all cracks. Contaminants, such as asphalt and heavy oiland rubber stains, shall be removed, at the discretion of the ContractingOfficer, by scraping and cleaning with solvents. Well-bonded surfacecontaminants and existing painted surfaces shall be removed by wet sandblasting. High-pressure water blasting will be permitted only if itcan be demonstrated to the satisfaction of the Contracting Officer thatthe concrete surface and cracks can be completely dried prior to theapplication of the polymer treatment.

g. Application. - The methacrylic concrete sealing compound shall bemixed, applied to the prepared concrete surface, and cured in accordancewith these specifications.

(1) Mixing of materials. - The monomer shall be mixed with initiatorand promoter in the following proportions (proportions may be adjustedby the Contracting Officer to give a satisfactory pot life based onconcrete surface temperatures and recommendations of the monomersystem manufacturer):

Parts by weight

(a) Substituted Methacrylate Monomer 100

(b) Cuemene Hydroperoxide (78%) 4.0

M-47 (M0470000.896)Page 49 of 738-1-96

(c) Cobalt Napthenate (6%) 2.0

DO NOT MIX COBALT NAPTHENATE DIRECTLY WITH CUEMENE HYDROPEROXIDE ASTHIS WILL PRODUCE AN EXTREMELY VIOLENT AND EXPLOSIVE CHEMICALREACTION.

The cobalt napthenate and cuemene hydroperoxide shall be mixed withthe substituted methacrylate monomer in separate steps; i.e., firstadd and mix cobalt napthenate with the substituted methacrylatemonomer, and then add and mix the cuemene hydroperoxide with thecobalt napthenate/ methacrylate monomer mixture.

The materials shall not be premixed. The monomer system shall beapplied to the concrete surface within 5 minutes after mixing thecuemene hydroperoxide with the cobalt napthenate/substitutedmethacrylate monomer mixture.

For manual application, the quantity of monomer system mixed shall belimited to 5 gallons at a time. A significant increase in viscosityor change in gel time prior to application shall be cause forrejection.

Machine mixing and application of the methacrylic sealing compound mayalso be performed by using a two-part monomer system utilizing apromoted monomer for one part and an initiated monomer for the otherpart. Adequate mixing shall be done to achieve a uniform blend of thetwo parts.

The use of machine mixing and application requires approval by theContracting Officer and treatment of a 10- by 50-foot test site todemonstrate that the equipment is working properly and capable ofproviding a uniform monomer mixture.

(2) Application of sealing compound. - Prepared surfaces shall beprotected from rain and moisture. Surfaces shall be treated withsealing compound within 24 hours after surface preparation iscompleted. The surface shall be allowed to dry thoroughly for aminimum of 48 hours before treatment. At the discretion of theContracting Officer, the following test shall be made to determine ifthe concrete surface is sufficiently dry to proceed with the polymertreatment. A 2-foot-square piece of clear polyethylene sheeting shallbe taped to the surface of the concrete and allowed to remain therefor a minimum of 2 hours exposed to sunlight. Moisture condensationon the inside surface of the polyethylene sheeting shall be consideredas evidence that the concrete surface is not sufficiently dry, and anadditional period for drying will be required before proceeding withthe polymer treatment. Additional tests may be required, at thediscretion of the Contracting Officer.

The monomer system shall be applied to the concrete surfaces duringnighttime and early morning hours as directed by the ContractingOfficer and with concrete temperatures between 45 and 85 EF. Monomerapplication will not be permitted in the direct rays of the sun asthis may cause a premature curing of the system.

The concrete surfaces shall be treated with monomer at an applicationrate of 75 to 100 square feet per gallon. The concrete surfaces shallbe flooded with the monomer mixture, allowing full penetration of theconcrete and filling all cracks, and brushed with a stiff bristlebroom. Puddles of excess monomer shall be removed by the Contractor.

M-47 (M0470000.896)Page 50 of 738-1-96

50

The sealing compound may also be spray-applied by machine using a two-part mixing procedure described in subparagraph 3.12.g.(1). Thepressure at the spray nozzle shall not be great enough to causemonomer mist to drift more than 2 feet beyond the nozzle. Compressedair shall not be used to produce the spray.

(3) Application of sand and curing. - Within 15 to 20 minutes afterapplication of the methacrylic sealing compound, and beforesignificant gelling has occurred, the entire treated area of concreteshall be covered by sand broadcast to achieve a uniform coverage of0.25 to 0.50 pound per square yard. This sand shall be left on theconcrete surface until the sealing compound has cured to a tack-freecondition. Any excess sand, not bonded to the concrete, shall then beremoved by the Contractor. Sand shall not be applied to verticalsurfaces that have been treated with methacrylic sealing compound.

Treated areas shall be protected and not put back into service for24 hours after treatment to allow the sealing compound to fully cure.

(4) Cleanup. - The Contractor shall keep the mixing equipment andtools clean during the course of the treatment, using a suitablesolvent such as acetone or methyl ketone (both flammable), or 1,1,1,-trichloroethane (nonflammable). Soap and water are also satisfactoryfor cleanup of fresh monomer from the tools. The Contractor shallquickly clean up all spills by a method previously approved by theContracting Officer.

After the repair work is completed, the residue in the open containersof cuemene hydroperoxide and cobalt napthenate shall be safelydestroyed by using some of the excess monomer resin to wash out thecatalyst containers and then allow it to cure before disposal or byother methods recommended by the manufacturers and approved by theContracting Officer.

3.13 SURFACE IMPREGNATION

a. General. - These specifications present the requirements forimpregnating concrete with a methyl methacrylate based monomer-catalystsystem followed by in situ polymerization of the monomer by heat.

b. Submittals. -

(1) The Contractor shall provide the Contracting Officer with themanufacturer's certifications that the monomers and catalyst meetthese specifications. Representative samples of the monomer systemcomponents, or of the combined monomer system if purchased premixed,shall be delivered to the Contracting Officer at least 30 days priorto use. At the Contracting Officer's option, these samples will betested to determine specifications compliance.

(2) At least 30 days prior to beginning the concrete impregnationprocess, the Contractor shall deliver to the Contracting Officer awritten report describing the Contractor's planned treatmentprocedures. Included in this report shall be a detailed descriptionof the drying, impregnation, monomer mixing and storage,polymerization and quality control procedures, facilities, andequipment the Contractor intends to use to treat the concrete. TheContracting Officer will review this report and approve or disapprovethe plan within 30 days of the date of receipt. In no event shall theContractor proceed with the surface impregnation treatment until

M-47 (M0470000.896)Page 51 of 738-1-96

approval of the Contractor's procedures, materials, and equipment hasbeen received.

(3) During the drying, cooling, impregnation, and polymerizationcycles, the Contractor shall obtain and supply to the ContractingOfficer concrete temperature data accurate to ±5 EF from at least ninepoints uniformly spaced on the surface of each treatment area and fromat least one point 1 inch below the concrete surface at theapproximate center of each treated area.

These data shall be in the form of a continuous record or periodicreadings recorded at 1-hour intervals. The technique and equipmentused to obtain the temperature data required in subparagraph3.13.g.(1) shall be described in the written procedures reportrequired above and subject to the Contracting Officer's approval.

(4) The Contractor shall maintain and supply to the ContractingOfficer monomer and catalyst records listing the dates of manufacture,storage temperatures, date of use and application rates, andquantities as applied to the concrete.

c. Quality assurance. - Quality assurance shall be in accordance withparagraph 1.4 and these specifications. Representative material samplessubmitted by the Contractor, as specified in subparagraph 3.13.b.(1) willbe tested, at the Contracting Officer's option.

d. Materials. -

(1) Monomer system. - The monomer system shall be composed of 95percent by weight methyl methacrylate (MMA) and 5 percent by weighttrimethlolpropane trimethacrylate (TMPTMA). A polymerizationcatalyst, 2,2-azobis-(2,4-dimethylvaleronitrile), shall be added tothis monomer system at the rate of 1 part catalyst to 200 partsmonomer by weight, or as directed by the Contracting Officer.

(a) MMA. - MMA shall meet the following requirements:

Formula CH2=C(CH3)C00CH3

Inhibitor 25 parts per million hydroquinone (HQ)

Molecular weight 100

Assay (Gas Chromatog- raphy) % 99.8 min

Density 7.83 lb/gal (0.938 kg/L)

Boiling 212 EF (100 EC)

Flash point 55 EF (13 EC) (Tag, ASTM D 1310)

(b) TMPTMA. - TMPTMA shall meet the following requirements:

Formula (CH2=CH3 COOCH2)3CCH2CH3

Inhibitor 100 parts per million hydroquinone (HQ)

M-47 (M0470000.896)Page 52 of 738-1-96

52

Assay, % 95.0 min

Density 8.82 lb/gal (1.058 kg/L)

Flash point Greater than 300 EF (149 EC)

(c) The polymerization catalyst shall be 2,2-azobis-(2,4-dimethyl-valeronitrile). Empirical formula: C14H24N4.

Monomer system components shall be used within 6 months aftermanufacture.

(2) Sand. - The impregnation sand shall be composed of clean, hard,dense, low-absorptive particles that will pass a 1.18-mm (No. 16)sieve, but with not more than 5 percent passing a 150 µm (No. 100)sieve.

e. Safety. - All work shall be performed in accordance with paragraph1.6 and these specifications. Because of the hazards associated withimproper use and handling of the monomer and catalyst, the followingadditional safety requirements shall be adhered to during the surfaceimpregnation process.

Personnel working with the monomers or catalyst shall be provided withand use safety eyeglasses or goggles, impervious gloves, aprons, andboots. Normally, in an outdoor monomer application, respiratoryequipment will not be necessary. In storage and mixing operations,however, accidental spills or equipment failures may result in hazardousvapor concentrations requiring self-contained respiratory equipment forpersonnel protection. The Contractor shall provide a field eye wash andwater washing facility for use in the event of an accidental splash ofmonomer on the workers. Eye wash facility shall be capable of providinga clean, room temperature flushing stream for a minimum of 15 minutes.

All sources of sparks or flame shall be removed from areas for monomerstorage and handling. In these areas monomer storage and mixing vesselsshall be provided with electrical grounds to prevent static sparks. Mixing and transfer equipment and motors shall be explosion proof, andsufficient ventilation shall be provided to prevent the formation ofexplosive monomer vapor-air mixtures. In accordance with applicablesafety regulations, warning signs such as "No Smoking" regulations shallbe posted. At the construction site, care shall be taken to eliminatesources of sparks or flame when monomer is present. Particular attentionshall be given to removal of welding operations, posting of "No Smoking"signs, and to traffic control to eliminate accidental fires from thesesources. Visitors at the job site shall be warned of the potentialhazards and provided with applicable safety equipment.

Catalyzed monomer not used within 4 hours of catalyst addition shall bestored in an explosion proof storage facility at a maximum storagetemperature of 0 EF until it can be used or destroyed as approved by theContracting Officer. Storage of catalyzed monomer for periods longerthan 2 days will not be permitted.

Monomer and catalyst storage and handling. - The monomers, MMA andTMPTMA, or the premixed monomer system shall be stored in their originalshipping containers or in other clean containers as approved by theContracting Officer. Maximum monomer storage temperature shall notexceed 90 EF. The storage area shall be selected to provide protectionfrom direct sunlight, fire hazard, and oxidizing chemicals. Sufficient

M-47 (M0470000.896)Page 53 of 738-1-96

ventilation shall be maintained in the storage area to prevent thehazardous buildup of monomer vapor concentrations in the storage airspace. The polymerization catalyst shall be stored in accordance withthe manufacturer's recommendations, but in no event shall the catalyststorage temperature be allowed to exceed 35 EF. Personnel exposed tomonomer or monomer vapor shall use minimum protective equipment asfollows: safety eyeglasses, impervious gloves and aprons, and rubberboots as required. As determined by the Contracting Officer, personnelmay be required to use full face protective shields, self-containedrespiratory equipment, or both. All personnel handling the monomers orcatalyst shall be thoroughly trained in their safe use in accordance withmanufacturer's recommendations.

Unsafe handling practices will be sufficient cause to discontinue workuntil the hazardous procedures are corrected. The handling and use ofmonomer shall in all cases comply with the requirements of applicableFederal, State, and local safety requirements and ordinances.

During the polymerization cycle, the heating enclosure shall be providedwith a means of positive ventilation to prevent hazardous concentrationsof monomer vapor within the enclosure. Open flame heat sources will notbe approved for use during polymerization.

The monomer mixing area shall be free of sources of ignition and shall bewell ventilated. Spilled monomer shall be contained with absorptivematerials such as vermiculite or dry sawdust and removed with non-sparking equipment.

f. Concrete preparation. - Deteriorated concrete shall be removed fromthe surface by wet sandblasting or other suitable means. Concretecontaining surface contaminants such as oil, paint, or protectivecoatings shall be cleaned by wet sandblasting or by other approved meansto remove these materials. After the removal of these materials, theconcrete surface shall be swept and air-blown to remove sand, leaves,trash, gravel, or other miscellaneous loose materials to the satisfactionof the Contracting Officer.

The Contractor shall install a temporary dike along the high side of thearea to be impregnated to divert possible rainwater around the area to beimpregnated. The Contractor shall also install a temporary dike alongthe low side of the area to be impregnated to act as a barrier to preventmonomer from accidentally escaping due to an accidental spill or excessapplication.

g. Application of the surface impregnation process. -

(1) Drying. - After the concrete surface area to be treated has beencleaned in accordance with subparagraph 3.13.f., it shall be uniformlycovered with a 1/4- to 1/2-inch thick layer of sand meeting therequirements of subparagraph 3.13.d.(2) and dried to permit polymerpenetration. The equipment used to accomplish drying shall consist ofa weatherproof enclosure with either an electric infrared, or hot-airheat system, or other technique as approved by the ContractingOfficer. Exposed flame infrared heat systems, if selected for drying,shall not be used for polymerization.

Drying shall be accomplished by raising the concrete surfacetemperature at a rate not exceeding 100 EF per hour to between 250 and275 EF, and maintaining that surface temperature range for 8 hours. If a higher maximum temperature is desired, approval by the

M-47 (M0470000.896)Page 54 of 738-1-96

54

Contracting Officer shall be obtained. During the drying period,sufficient airflow shall be maintained over the concrete surface toventilate the water vapor removed from the concrete and to provideuniform concrete surface temperature. During the drying cycle, theContractor shall obtain continuous or periodic surface temperaturemeasurements, as specified in subparagraph 3.13.b.(3), at a sufficientnumber of locations over the heated concrete surface [normally onelocation per 100 square feet] to ensure temperature uniformity. Themaximum temperature variation over the heated concrete surface shallnot exceed ±20 EF of mean concrete surface temperature at the timemeasurements are taken.

(2) Cooling. - After the concrete has been dried, it shall be cooledprior to monomer application. The cooling rate for concrete surfacetemperature shall not exceed 100 EF per hour. Cooling shall continueuntil the maximum temperature at a depth of 1 inch below the surfaceof the concrete is 100 EF or less.

During the cooling and impregnation cycles, the dried concrete shallbe protected to prevent moisture from reentering the concrete. It maybe necessary, if determined by the Contracting Officer, to repeat thedrying and cooling cycles prior to monomer application should moisturereenter the concrete.

(3) Monomer mixing. - The monomer MMA and TMPTMA may be premixed inthe specified ratio and stored prior to use. Storage of premixedmonomer shall be as required in subparagraph 3.13.e. All monomermixing and transfer equipment shall be as required in subparagraph3.13.e. All monomer mixing and transfer equipment shall be ofexplosion proof design and shall be provided with electrical groundcables. Monomer transfer shall be from bottom to bottom of thevessels or through dip pipes in the vessels to prevent the buildup ofstatic charge during transfer. Pipe fittings, valves, pump impellers,or other equipment which will come into contact with monomer shall notbe made of copper or brass or certain plastics attacked by themonomer.

(4) Catalyst-monomer mixing. - The polymerization catalyst shall bemixed with the monomer system immediately prior to use. Monomersystem temperature at the time of catalyst addition shall not exceed90 EF. Mixing shall be accomplished with explosion proof equipmentin electrically grounded containers in a well-ventilated area.

(5) Impregnation. - Following the drying and cooling cycles, the sandon the concrete surface to be impregnated shall be uniformly leveledif necessary.

The temperature on the surface of the concrete shall not exceed 100 EFat the time of monomer application nor at any time during theimpregnation cycle.

Monomer application shall be made at a rate sufficient to uniformlysaturate the sand layer to a slight excess without applying so muchmonomer that it would drain away from the impregnated area. Themonomer application rate should be 0.8 pound of monomer per squarefoot of concrete surface. This is approximately 0.9 gallon per squareyard of surface area. However, sand layer thickness, sand particlesize, and slope may necessitate application rate adjustment to achievethe described saturation. Following application, the monomer shall beallowed to soak into the concrete for approximately 6 hours. If at

M-47 (M0470000.896)Page 55 of 738-1-96

any time during the soak cycle the sand should become dry, additionalmonomer shall be applied as directed by the Contracting Officer.

In order to protect the monomer-saturated sand from the polymerizingeffects of direct and indirect solar radiation, monomer applicationand subsequent soaking shall occur during the time period sunset tosunrise unless the Contractor provides shielding, as approved by theContracting Officer, to prevent solar radiation from reaching the areabeing impregnated. Immediately following monomer application, acontinuous mylar membrane a minimum of 6 mils thick shall be placedover the monomer-saturated surface to reduce monomer evaporation. This membrane shall remain in place, except for the short periods ofmonomer application or surface inspection, throughout the impregnationcycle and until the polymerization cycle is complete.

(6) Polymerization. - Polymerization of the monomer impregnated intothe concrete shall be accomplished by uniformly heating the treatedconcrete to a surface temperature of at least 165 EF and not exceeding185 EF and maintaining it for a minimum of 5 hours. The rate oftemperature increase and allowable surface temperature variation shallbe as required in subparagraph 3.13.g.(1).

The equipment and procedures used to accomplish heating of theconcrete for polymerization shall be of the type described insubparagraph 3.13.g.(1) as approved by the Contracting Officer. Seesubparagraph 3.13.b.

(7) Cleanup. - Following completion of the surface impregnationtreatment process, the Contractor shall remove the sand from theconcrete surface and dispose of the sand at the site as directed bythe Contracting Officer.

3.14 SILICA FUME CONCRETE

a. General. - Silica fume concrete shall be used to repair concretedamaged by abrasion-erosion action. Silica fume concrete may also beused in the infrequent occasions where a high strength (compressivestrength in excess of 10,000 lbs per square inch) repair concrete isrequired. Silica fume concrete shall be used on areas of damagedconcrete greater than 1 square foot having a depth greater than 6inches or a depth extending 1 inch below or behind the backside ofreinforcement. If the depth of repair is at least 2 inches but lessthan 6 inches, epoxy bonding agent shall be used in accordance withthe provisions of paragraph 3.8, to bond fresh silica fume concrete toconcrete being repaired. Silica fume concrete shall not be used forrepairs that are less than 2 inches in depth.

b. Submittals. - The Contractor shall submit certification of compliancefor materials in accordance with subparagraph d. below.


d. Materials. - All concrete materials shall be obtained from previouslytested and approved sources. Materials will be accepted on certificateof compliance with the following ASTM Standards:

(1) Portland cement. - Portland cement shall meet the requirements ofASTM C 150 for type I, II, or V cement. The specific cement type

M-47 (M0470000.896)Page 56 of 738-1-96

56

shall be as directed by the Contracting Officer and determined by theenvironment in which the repair is conducted.

(2) Silica fume. - The silica fume mineral admixture shall beobtained as a byproduct from the manufacture of solely silicon metalin electric blast furnaces. The condensed silica fume shall beprocessed and sized to a fineness of approximately 200,000 cm2 per gm(20,000 m2/kg) at a porosity (t) of 0.500 when tested in accordancewith ASTM C 204 and have an amorphous silica (Si02) content of not lessthan 85 percent of the total fume. When tested in accordance withASTM C 311, the silica fume shall have a moisture content of less than3 percent and a loss on ignition of not greater than 6 percent. Amanufacturer's certificate of compliance with these requirements andapplicable provisions of ASTM C 618 is required. The silica fumeshall be supplied, proportioned and combined with other admixtures, asnecessary, from a supplier regularly engaged in the sale of thiscombination product as a concrete admixture. This combinationadmixture shall be batched with the concrete in either of two forms ortypes.

(a) The wet type shall consist of water slurry containingapproximately 45 percent silica fume solids with a water-reducing admixture meeting all requirements specified.

(b) The dry form shall be a densified powder blended with adry water reducing admixture. Both types shall be compatiblewith a water reducing admixture that could be added at theconcrete plant or at the placement site.

(3) Admixtures. - The Contractor shall furnish air-entraining andchemical admixtures for use in concrete.

(a) Air-entraining admixture shall be used in all silica fumeconcrete and shall conform to ASTM C 260.

(b) Chemical admixtures. - The Contractor may use type A, D, F, orG chemical admixtures. If used, they shall conform to ASTM C 494.

(c) Use of other admixtures must be approved by theContracting Officer.

(4) Water. - The water used in making and curing silica fume concreteshall be free from objectionable quantities of silt, organic matter,salts, and other impurities.

(5) Aggregate. - The term "sand" is used to designate aggregate inwhich the maximum size particle will pass a 4.75-mm (No. 4) sieve. The term "coarse aggregate" is used to designate all aggregate whichcan be retained on a 4.75-mm (No. 4) sieve. Sand and coarse aggregatemeeting the requirements of ASTM C 33 shall be used in all concrete.

(6) Curing compound. - Wax-base (type I) and water-emulsified resin-base (type II) curing compounds shall conform to the requirements ofReclamation's "Specifications for Concrete Curing Compound" (M-30)dated October 1, 1980.

(7) Evaporation retarder. - Monomolecular membrane evaporationretardant formulated for use with silica fume concreterequirements shall be equal to "Confilm", manufactured by MasterBuilders, Lee at Mayfield, Cleveland, OH 44118.

M-47 (M0470000.896)Page 57 of 738-1-96

e. Safety. - All work shall be performed in accordance with paragraph1.6.

f. Concrete preparation. - After damaged or unacceptable concrete hasbeen removed as specified in section 2. the surface on which the silicafume concrete will be placed shall be prepared. An acceptable surfaceshall have the appearance of freshly broken, properly cured concrete. The surface shall be free of any deleterious materials such as freemoisture, ice, petroleum products, mud, dust, carbonation, and rust. Theperimeters of the repair shall be saw cut to a minimum depth of 1 inch.

The clean surface is not ready to receive repair silica fume concreteuntil it has been brought to a saturated, surface-dry condition. Thiscondition is attained by saturating the surface to a depth that noconcrete mixture water may be absorbed from the fresh concrete. Then,just prior to placing concrete against the surface, all free moisture(moisture capable of reflecting light) shall be removed from the preparedsurface.

g. Application. - Silica fume concrete shall be composed of cement,silica fume, coarse aggregate, sand, water, and approved admixtures, allwell mixed and brought to the proper consistency. Silica fume concretemixtures shall be proportioned in accordance with Reclamation's "ConcreteManual", Eighth Edition, revised, chapter III, except that silica fumeshall be added to the mixture at a ratio of 7 to 12 percent by mass ofthe portland cement as directed by the Contracting Officer. The water-cementitious ratio of the concrete (exclusive of water absorbed by theaggregates) shall not exceed 0.35 by weight. Slump of the silica fumeconcrete, when placed, shall not exceed 3 inches for concrete in slabsthat are horizontal or nearly horizontal and 4 inches for all otherconcrete. Silica fume concrete with less slump should be used when it ispracticable to do so. The concrete ingredients shall be thoroughly mixedin a batch mixer. The concrete, as discharged from the mixer, shall beuniform in composition and consistency from batch to batch.

(1) Forms. - Forms shall be used for silica fume concrete whenevernecessary to confine the concrete and shape it to the required lines. The forms shall be clean and free from encrustations of mortar, grout,or other foreign material. Before silica fume concrete is placed, thesurfaces of the forms shall be coated with a form oil that willeffectively prevent sticking and will not soften or stain the concretesurfaces or cause the surfaces to become chalky or dust producing.

(2) Placing. - Placing of silica fume concrete shall be performedonly in the presence of an authorized representative of theContracting Officer. Placement shall not begin until all preparationsare complete and the authorized representative of the ContractingOfficer has approved the preparations. Silica fume concrete shall notbe placed in standing or running water unless, as determined by theContracting Officer, the structure under repair cannot be economicallydewatered. If underwater silica fume concrete placement is required,special placing procedures shall be required. A suggested guide isACI 394R.

When appropriate, silica fume concrete shall be placed in layers notgreater than 20 inches thick. Each layer, regardless of thethickness, shall be adequately consolidated using immersion-typevibrators or form vibrators when approved. Adequate consolidation ofsilica fume concrete is obtained when all undesirable air voids,

M-47 (M0470000.896)Page 58 of 738-1-96

58

including the air voids trapped against forms and construction joints,have been removed from the concrete.

(3) Finishing. - The class of finish required shall be a finishclosely resembling the finish of the surrounding concrete. Silicafume concrete does not normally develop bleed water and specialfinishing procedures may thus be required. The ambient temperature ofsurfaces being finished shall be not less than 50E F. Immediatelyfollowing placement of silica fume concrete to finished grade, thesurface shall be screeded to bring the surface to finished level withno coarse aggregate visible. No cement or mortar shall be added tothe finishing operation.

A monomolecular membrane evaporation retarder shall be applied tothe surfaces of the silica fume concrete, in accordance withmanufacturer's recommendations, immediately after the screeningoperation.

Floating, if necessary to achieve the specified finish, shall beperformed immediately following the application of evaporationretarder.

h. Curing and protection. - Proper curing of silica fume concrete isessential if bond failure and shrinkage cracking are to be eliminated. Silica fume concrete repairs shall be cured, preferably by water curing,or alternately, by application of a uniform and continuous membrane ofwax-base (type I) or water-emulsified resin-base (type II) curingcompound meeting the requirements of subparagraph 3.6.d.(6). and asapproved by the Contracting Officer. If the use of curing compound isapproved, daily inspection by the Contractor shall be performed to ensurethe maintenance of a continuous, water-retaining film over the repairedarea. The water-retaining film shall be maintained for 28 days after theconcrete has been placed.

Silica fume concrete surfaces to which curing compound has been appliedshall be adequately protected during the entire curing period frompedestrian and vehicular traffic and from any other possible damage tothe continuity of the curing compound membrane. Areas where curingcompound is damaged by subsequent construction operation within thecuring period shall be resprayed.

Water curing shall commence immediately after the concrete has attainedsufficient set to prevent detrimental effects to the concrete surface. The concrete surface shall be kept continuously wet for a minimum of 14days. Whenever possible, silica fume concrete shall be water cured bycomplete and continuous inundation for a minimum period of 14 days.

The Contractor shall protect all silica fume concrete against damageuntil acceptance by the Government. Whenever freezing temperatures areimminent, the Contractor shall maintain the newly placed repair concreteat a temperature of not less than 50 EF for 72 hours. Water-cured silicafume concrete shall be protected from freezing for the duration of thecuring cycle and an additional 72 hours after the water is removed.

3.15 ALKYL-ALKOXY SILOXANE SEALING COMPOUND

a. General. - A concrete sealing compound is defined as a liquid that isapplied to the surface of hardened concrete to prevent or decrease thepenetration of liquid or gaseous media, such as water, aggressive

M-47 (M0470000.896)Page 59 of 738-1-96

solutions, and carbon dioxide, during the service exposure, preferablyafter initial drying to facilitate its absorption into voids and cracks. An alkyl-alkoxy siloxane sealing compound, herein after referred to assiloxane, shall be applied to concrete surfaces when it is desired thatapplication of a sealing compound cause no change in the appearance ofthe sealed surfaces.

The sealing of concrete surfaces with siloxane shall be in accordancewith these specifications.

Siloxane sealing compound shall not be used to seal concrete subject tofrequent or permanent immersion in water; nor shall it be used onconcrete surfaces exposed to high abrasion forces.

b. Submittals. - The Contractor shall, before starting work, shallsubmit to the Contracting Officer manufactures data and certificationthat the concrete cleaner and siloxane sealing compound furnished by theContractor meets the requirements of this specifications. The chemicalconstituents shall correspond to the requirement of subparagraph 3.15.d.

A MSDS shall be furnished to the Contracting Officer prior to shipment ofmaterial with information pertaining to the safe practices for storage,handling and disposal of the materials and their explosive and flammablecharacteristics, health hazards, and the manufacturer's recommended firefighting techniques. The MSDS shall be posted at all storage areas andat the job site.

The Contractor shall furnish, for approval, a detailed writtendescription of the methods the Contractor plans to use to apply thesiloxane and for clean up of all spills and residue in open containers.


d. Materials. - The siloxane sealing compound shall be a clear, ready touse sealer based on oligomeric alkyl-alkoxy siloxane containing not lessthan 20 percent active siloxane solids by mass.) The compound whenproperly applied to concrete shall conform to the following performancestandard:

Chloride screening 91% (minimum) (NCHRP 224, Series I)Reduction of Chlorine Penetration

vs untreated concrete 92.4(minimum) (NCHRP 224, Series IV)Moisture Vapor Transmission 97.5%(minimum) (ASTM E-96)Water Repellency Rating 92%(minimum) (ASTM C-140, ASTM C-67)Water Absorption 1.40%(maximum) (ASTM C-67, ASTM C-140)Scaling Resistance to Deicers Excellent (ASTM C-672)

Resistance to Chlorine Penetration 0.07 lbs/cu.yd. (AASHTO T-259/260) (maximum)

Surface Friction Reduction 0 (ASTM E-303)Penetration (1 application) 1/8" - 1/4"

The compound shall have a high flash solvent carrier with a strongchloride screen and shall exhibit alkaline stability and form achemical bond with the treated concrete.

The concrete sealing compound shall be Consolideck SX as manufactured byProSoCo Inc., P.O. Box 1578, Kansas City, KS 66117, (913) 281-2700, orapproved equal.

M-47 (M0470000.896)Page 60 of 738-1-96

60

e. Safety. - The Contractor shall take the necessary precautions toavoid wind drift onto auto and pedestrian traffic. The materials shallbe stored, handled, and applied in accordance with the manufacturer's orsupplier's recommendations. Storage of all materials may be in theoriginal shipping containers. The material should be stored in sealedcontainers and kept away from extreme heat. The sealant contains blendedsolvents and should be handled accordingly. Do not use near fire orextreme heat and provide good ventilation to avoid buildup of solventfumes. Personnel applying the concrete sealant shall wear NIOSH/MSHAapproved respirators, goggles, rubber gloves, and plastic or rubber suitsto avoid splash to skin and eyes. Clothing that becomes contaminatedwith the concrete sealant shall be changed as quickly as possible.

Unsafe handling practices will be sufficient cause to discontinue workuntil the hazardous procedures are corrected. The handling and use ofthe concrete sealant shall in all cases comply with the requirements ofapplicable federal, state, and local safety requirements and ordinances.

f. Concrete preparation. - The concrete surfaces to be treated shall beclean and physically sound. Unsound or deteriorated surfaces shall beremoved in accordance with the requirements of section 2. All neededrepair work shall be adequately cured prior to application of thesiloxane.

Concrete surfaces shall be prepared by power sweeping and blowing with highpressure air to remove all dirt and foreign material from the surface andfrom all cracks. Contaminants, such as asphalt and heavy oil and rubberstains, shall be removed at the discretion of the Contracting Officer byscraping and cleaning with solvents. Well bonded surface contaminants andexisting painted surfaces shall be removed by high pressure water blastingor wet sand blasting. The concrete surface and all cracks shall becompletely dried prior to the application of the siloxane.

g. Application. - If the concrete sealant is a product other thanConsolodeck SX, a test application of the concrete sealant shall be madeto an area selected by the Contracting Officer using the same equipmentand procedures proposed for the project. The test procedure is to insurecompatibility of the product, to determine the waterproofing results andto check for surface discoloration from the procedure. The Contractorshall not proceed with the remainder of the work until the ContractingOfficer approves the results of the test application. If the results ofthe test application are deemed unsatisfactory by the ContractingOfficer, the Contractor shall modify his sealant materials, procedure,and/or equipment as directed by the Contracting Officer and the testapplication shall be repeated.

The siloxane sealant shall not be applied at surface and air temperaturesbelow 40 degrees F, or above 100 degrees F. Surfaces shall be treatedwithin 24 hours after the surface preparation is completed. The preparedsurfaces shall be maintained in a dry condition and protected to preventcontamination prior to the siloxane application. If the prepared surfacebecomes contaminated, it shall be recleaned in accordance with paragraph3.15.f. The Contracting Officer shall determine if the surface is dryenough to receive sealant. If the Contracting Officer determines thatthe surface is too damp for application of the sealant, application ofthe sealant shall not commence without approval of the ContractingOfficer.

The sealant shall be applied with low pressure (20) psi airless sprayequipment fitted with solvent resistant hoses and gaskets. Heavily

M-47 (M0470000.896)Page 61 of 738-1-96

saturated brush or roller may be used in isolated incidents if theContracting Officer determines that brush or roller application is the mosteffective means.

Adjoining glass, metal and painted surfaces shall be protected fromoverspray and splash of the siloxane sealant. Any accidental orunintentional overspray or splash on adjoining glass, metal or paintedsurfaces shall be removed using mineral spirits before the solution hasdried on the surface.

When applying to exteriors of occupied areas, all exterior air conditioningand ventilation vents shall be covered during application and air handlingequipment shall be turned off during application to avoid solvent odorswithin the occupied areas.

The concrete surfaces shall be given a full and complete application of thesiloxane sealant at the following application rate of 80-120 sq.ft./gal.

(1) Horizontal surfaces. - When applying the siloxane to flathorizontal concrete surfaces, the siloxane shall be applied in two "wet-on-wet" coats. Flood the surface and broom or squeegee the materialaround for even distribution. Allow the surface to absorb the siloxaneand follow immediately with a second application before the surfacedries. Puddles of excess siloxane sealant shall be broomed outthoroughly until they completely penetrate into the surface.

(2) Vertical surfaces. - When applying the siloxane to verticalsurfaces, the siloxane shall be applied in two "wet-on-wet"applications. Apply the siloxane in a flooding application, from thebottom up with sufficient material applied to produce a 6" to 8" rundownbelow the contact point of the spray pattern with the concrete surface. Allow the first application to penetrate the surface (approximatelythree to five minutes) and reapply in the same saturating manner. Ifthe siloxane sealant is applied to surfaces of extremely dense, mirrorfinish concrete the Contracting Officer may direct that the siloxane beapplied in one saturating application to prevent surface darkening.

h. Curing. - The treated areas shall be protected from rain and foottraffic for six hours after application. Vehicular traffic will not beallowed on the treated area until after 24 hours after the application ofthe siloxane.

i. Measurement for Payment. -

(1) Measurement for payment of surface preparation of the concretesurfaces will be made of the actual surface area prepared. Paymentfor surface preparation will be made at the unit price per squarefoot bid therefor in the schedule, which unit price shall includeall costs of preparing the concrete surfaces for the siloxane asspecified in paragraph 3.15.f.

(2) Payment for seal coating of the concrete surfaces will utilizethe same area as measured for the surface preparation. Payment forseal coating of concrete surfaces will be made at the unit priceper square foot bid therefor in the schedule, which unit priceshall include all costs for storing and handling materials, ofapplying the siloxane system, of cleanup, and of providing all thenecessary safety equipment, and any other work required under thesespecifications to properly complete the job.

M-47 (M0470000.896)Page 62 of 738-1-96

62

Notes

guide to concrete repair

Documents