This document has been approved for use by agen-cies of the Department of Defense and for listing in 306.1-90the DoD Index of Specifications and Standards. (Reapproved 2002)

Standard Specification for Cold Weather Concreting (306.1-90)Reported by ACI Committee 306

Nicholas J. Carino, Chairman*

Fred Anderson*Peter Antonich

George R. U. Burg

Oleh B. Ciuk

Douglas J. Haavik*

Gilbert Haddad

Jules Houde

David A. Hunt

Robert A. Kelsey

Albert W. Knott

Charles J. Korhonen

William Perenchio*

John M. Scanlon

Michael Shydlowski

Bruce A. Suprenant

J. Derle Thorpe

Valery Tokar

Lewis H. Tuthill*

Harold B. Wenzel

Arthur T. Winters

This Standard Specification gives requirements for cold weather con-creting. It includes cold weather requirements for preparations priorto placement of concrete, and protection of concrete.

Keywords: accelerating admixtures; cold weather; compressive strength; con-struction; curing; formwork; freezing; heating; insulation; maturity; protec-tion; temperature.

FOREWORDFl. This foreword is included for explanatory pur-

poses only; it does not form a part of the StandardSpecification ACI 306.1.

F2. Standard Specifications ACI 306.1 is a ReferenceStandard which the Architect/Engineer may cite in theProject Specifications for any building project, to-gether with supplementary requirements for the spe-cific project.

F3. Each technical section of Standard SpecificationACI 306.1 is written in the Three-Part Section Formatof the Construction Specifications Institute, as adaptedby ACI and modified to ACI requirements. The lan-guage is generally imperative and terse.

F4. Checklists do not form a part of Standard Spec-ification ACI 306.1. Checklists are to assist the Archi-tect/Engineer in properly choosing and specifying anynecessary requirements for the Project Specifications.

PREFACE TO SPECIFICATION CHECKLISTPl. Standard Specification ACI 306.1 is intended to

be used by reference or incorporation in its entirety inthe Project Specifications. Individual sections, articles,or paragraphs shall not be copied into the ProjectSpecifications, since taking them out of context maychange their meaning.

*Task force for revision.Supercedes ACI 306.1-87. Revised by the Expedited Standardization Proce-

dure, effective July 1, 1990. In 1990, the format was revised. The Foreword,Preface, and Specification Checklist were revised. Reference Standards wereupdated and the sections on Materials and Execution were rewritten and re-numbered.

30

P2. If sections or parts of Standard SpecificationACI 306.1 are edited into project specifications or anyother document, they shall not be referred to as ACIStandards, since the Standard Specification has beenaltered.

P3. Building codes set minimum requirements neces-sary to protect the public. This Standard Specifica-tion may stipulate requirements more restrictive thanthe minimum. Adjustments to the needs of a particularproject shall be made by the Architect/Engineer by re-viewing each of the items in the Specification Check-list and then including the Architect/Engineer’s deci-sion on each item as a mandatory requirement in theProject Specifications.

P4. These mandatory requirements designate thespecific qualities, procedures, materials, and perfor-mance criteria for which alternatives are permitted orfor which provisions were not made in the StandardSpecification. Exceptions to the Standard Specifica-tion shall be made in the Project Specifications, if re-quired.

P5. A statement such as the following will serve tomake Standard Specification ACI 306.1 a part of theProject Specifications.

Work on shall conformto all requirements of ACI 306.1, Standard Spec-ification for Cold Weather Concreting, publishedby the American Concrete Institute, Detroit,Michigan, except as modified by the requirementsof these Contract Documents.

P6. The Standard Specification Checklist identifiesArchitect/Engineer choices and alternatives. Thechecklist identifies the sections, parts, and articles ofthe Standard Specification and the action required bythe Architect/Engineer.

Copyright 100 2002, American Concrete Institute. All rights reserved includ-ing rights of reproduction and use in any form or by any means, including themaking of copies by any photo process or by any electronic or mechanical de-vice, printed or written or oral, or recording for sound or visual reproductionor for use in any knowledge or retrieval system or device, unless permission inwriting is obtained from the copyright proprietors.

6.1-1

306.1-2 ACI STANDARD

SPECIFICATION CHECKLISTM. MANDATORY REQUIREMENTS

Section/Part/Article ofACI 306.1 Notes to the Architect/Engineer

1.4 Reference standardsReview applicability of the cited references and take exception if required

3.1 Preparation before concretingIf the temperature of massive embedments, such as heavy steel guide rails or channels and steel grate framesor ducts, is lower than 32 F, concrete cast around them will be damaged by freezing. Identify in the ContractDocuments massive embedments which must be at a temperature above freezing prior to placement of con-crete.

A frozen subgrade can lead to freezing of newly-placed concrete or foundation settlement upon subsequentthawing of the subgrade. Specify in the Contract Documents the depth to which frozen subgrade should bethawed prior to placement of concrete. Specify procedure to verify that subgrade has been thawed to specifieddepth.

3.2.2 Protection temperatureSpecify the frequency for recording the temperature but do not use a frequency lower than twice per 24-hr pe-riod.

3.4.5 Protection for structural safetyIndicate in the Contract Documents the concrete strength required for each structural member before form re-moval or continued construction, or both.

O. OPTIONAL REQUIREMENTS

Section/Part/Article ofACI 306.1 Notes to the Architect/Engineer

1.5.1 Detailed proceduresIndicate in the Contract Documents whether submittal, review, and acceptance of procedure is required. Des-ignate degree of detail required in any submittal procedure.

3.3 Curing concreteStrength gain may not continue after removal of the protection because of rapid drying in regions where thereare periods of cold, dry, windy weather. Therefore, under these conditions, consideration should be given toextending the protection period in order to facilitate moist curing.

3.2.2 Protection temperatureSpecify the minimum protection temperature if different than Column 2 of Table 3.2.1.

3.4.4 Protection against freezingl Any changes in the concrete mix proportions for reducing the duration of the protection period to prevent

early freezing should be submitted for review or acceptance.l For certain structures, the protection period may be reduced if, after 24 hr of protection, the compressive

strength of the in-place concrete is at least 500 psi. The requirements for these structures are that they do notrequire early strengths, will undergo little or no freezing and thawing during construction and in service, andhave not been exposed to an external supply of moisture during the protection period.l The minimum protection temperature specified in Table 3.2.1 may be reduced provided that the protection

period is extended until the compressive strength of the in-place concrete is at least 500 psi.l Note that a compressive strength of 500 psi is only adequate to protect the concrete against damage from one

cycle of freezing and thawing.l The specified minimum protection periods are based on the assumption that additional curing will be speci-

fied and provided, as needed, prior to putting the structure into service. Longer protection periods may bespecified to assure that desired properties are developed prior to removal of protection.

S. SUBMITTALS

Section/Part/Article ofACI 306.1 Notes to the Architect/Engineer

1.5 Submittal of proceduresIf required, indicate to whom submittals will be sent.

1.5.1 Detailed proceduresMinimum procedures for placement, curing and protection of the concrete may follow the recommendationsin ACI 306R, “Cold Weather Concreting.” The details should include, but not be limited to, the following:lProcedures for protecting the subgrade from frost and the accumulation of ice or snow on reinforcement or

forms prior to placement.lMethods for temperature protection during placement.lTypes of covering, insulation, housing, or heating to be provided.•.Curing methods to be used during and following the protection period.lUse of strength accelerating admixtures.lMethods for verification of in-place strength.• Procedures for measuring and recording concrete temperatures.lProcedures for preventing drying during dry, windy conditions.

Require detailed procedures for those items of concern for the Work.

COLD WEATHER CONCRETING SPECIFICATION 306.1-3

CONTENTS1 - General, p. 306.1-3

1.1 - Scope1.2 - Definitions1.3 - Reference organizations1.4 - Reference standards1.5 - Submittal of procedures

2- Materials, p. 306.1-42.1 - Scheduling protection materials2.2 - Concrete

3- Execution, p. 306.1-43.1 - Preparation before concreting3.2 - Concrete temperature3.3 - Curing of concrete3.4 - Protection of concrete

1 - GENERAL1.1 - Scope

1.1.1 This Standard Specification covers require-ments for cold weather concreting and protection ofconcrete from freezing during the specified protectionperiod.

1.1.2 The provision of this Standard Specificationshall govern unless otherwise specified in the ContractDocuments.

1.2. - DefinitionsThese definitions are to assist in interpreting the pro-

visions of this specification.Accepted - Accepted by or acceptable to the Archi-

tect/Engineer.Architect/Engineer -The architect, engineer, archi-

tectural firm, engineering firm, or architectural and en-gineering firm issuing Project Drawings and Specifica-tions, or administering the Work under the ContractDocuments.

Cold weather - A period when for more than threesuccessive days the average daily outdoor temperaturedrops below 40 F. The average daily temperature is theaverage of the highest and lowest temperature duringthe period from midnight to midnight. When tempera-tures above 50 F occur during more than half of any 24hr duration, the period shall no longer be regarded ascold weather.

Cold weather concreting - Operations concerningthe placing, finishing, curing, and protection of con-crete during cold weather.

Contractor - The person, firm, or corporation withwhom the Owner enters into an agreement for con-struction of the Work.

Contract documents - Documents including theProject Drawings and Project Specifications coveringthe required Work.

Day - A time period of 24 consecutive hours.Owner - The corporation, association, partnership,

individual, or public body or authority with whom theContractor enters into an agreement and for whom theWork is provided.

Project drawings -The drawings, which along withthe Project Specifications, complete the descriptive in-formation for constructing the Work required or re-ferred to in the Contract Documents.

Project specifications - The written documentswhich specify requirements for a project in accordancewith the service parameters and other specific criteriaestablished by the Owner.

Protection period - The required time during whichthe concrete is maintained at or above a specific tem-perature in order to prevent freezing of the concrete orto ensure the necessary strength development for struc-tural safety.

Reference standards - Standards of a technical so-ciety, organization, or association, including the codesof local or state authorities, which are referenced in theContract Documents.

Required - Required by this Specification or theContract Documents.

Submitted - Submitted to the Architect/Engineerfor review.

Work - The entire construction or separately iden-tifiable parts thereof which are required to be fur-nished under the Contract Documents. Work is theresult of performing services, furnishing labor, andfurnishing and incorporating materials and equipmentinto the construction, all as required by the ContractDocuments.

1.3 - Reference organizationsACI: American Concrete Institute

P.O. Box 19150Detroit, MI 48219

ASTM: American Society for Testing and Materials1916 Race StreetPhiladelphia, PA 19103

1.4 - Reference standards1.4.1 ACI Standards

301-89 Specifications for StructuralConcrete for Buildings

1.4.2 ASTM StandardsC 31-88 Standard Method of Making

and Curing Concrete TestSpecimens in the Field

C 150-86 Standard Specification forPortland Cement

C 494-86 Standard Specification forChemical Admixtures forConcrete

C 803-82 Standard Test Method forPenetration Resistance ofHardened Concrete

306.1-4 ACI STANDARD

Table 3.2.1 - Concrete temperature(1) (2) (3)

Least dimension of Minimum temperature Maximum gradualsection, in. of concrete as placed decrease in surface

and maintained during temperature dur-the protection period, ing any 24 h afterF end of protection,

FI I

Less than 1212 to less than 3636 to 72Greater than 72

50::, 4045 3040 20

C 873-85

C 900-87

Standard Test Method forCompressive Strength ofConcrete Cylinders Cast inPlace in Cylindrical MoldsStandard Test Method forPullout Strength of Hard-ened Concrete

1.5 - Submittal of procedures1.5.1 Detailed procedures - If required, submit de-

tailed procedures for the production, transportation,placement, protection, curing, and temperature moni-toring of concrete during cold weather. In the submit-tal, include procedures to be implemented upon abruptchanges in weather conditions or equipment failures.Do not begin cold weather concreting until these pro-cedures have been reviewed and accepted.

2 -- MATERIALS2.1 Scheduling protection materials

All materials and equipment required for protectionshall be available at the project site before cold weatherconcreting.

2.2 - ConcreteConcrete for slabs and other flatwork exposed to

cycles of freezing and thawing in a wet condition dur-ing the construction period shall be air entrained asspecified in ACI 301 even though the concrete may notbe exposed to freezing in service.

- - EXECUTION3.1 - Preparation before concreting

Remove all snow, ice, and frost from the surfaces,including reinforcement, against which the concrete isto be placed. Before beginning concrete placement,thaw the subgrade to the depth specified in the Con-tract Documents. Do not place concrete around mas-sive embedments identified in the Contract Documentsunless such embedments are at a temperature abovefreezing.

3.2 - Concrete temperature3.2.1 Placement temperature - The minimum tem-

perature of concrete immediately after placement shallbe as specified in Column 2 of Table 3.2.1. The tem-perature of concrete as placed shall not exceed the val-ues shown in Column 2 of Table 3.2.1 by more than 20F.

3.2.2 Protection temperature - Unless otherwisespecified, the minimum temperature of concrete duringthe protection period shall be as shown in Column 2 ofTable 3.2.1. Temperatures specified to be maintainedduring the protection period shall be those measured atthe concrete surface, whether the surface is in contactwith formwork, insulation, or air. Measure the temper-ature with a surface temperature measuring device hav-ing an accuracy of _t2 F. Measure the temperature ofconcrete in each placement at regular time intervals asspecified in the Contract Documents.

3.2.3 Termination of protection - The maximumdecrease in temperature measured at the surface of theconcrete in a 24-hour period shall not exceed the valuesshown in Column 3 of Table 3.2.1. Do not exceed theselimits until the surface temperature of the concrete iswithin 20 F of the ambient or surrounding tempera-tures. When the surface temperature of the concrete iswithin 20 F of the ambient or surrounding tempera-ture, all protection may be removed.

3.3 - Curing of concretePrevent concrete from drying during the required

curing period. If water curing is used, terminate use atleast 24 hr before any anticipated exposure of the con-crete to freezing temperatures.

3.4 - Protection of concrete3.4.1 Combustion heaters - Vent flue gases from

combustion heating units to the outside of the enclo-sure.

3.4.2 Overheating and drying - Place and directheaters and ducts to avoid areas of overheating ordrying of the concrete surface.

3.4.3 Maximum air temperature - During the pro-tection period, do not expose the concrete surface to airhaving a temperature more than 20 F above the valuesshown in Column 2 of Table 3.2.1, unless higher valuesare required by an accepted curing method.

3.4.4 Protection against freezing - Cure and protectconcrete against damage from freezing for a minimumperiod of 3 days, unless otherwise specified. Maintainthe surface temperature of the concrete during that pe-riod in accordance with Column 2 of Table 3.2.1, un-less otherwise specified. The protection period may bereduced to 2 days if use of one or more of the follow-ing to alter the concrete mixture is accepted:

l Type III portland cement meeting the require-ments of ASTM C 150

l A strength accelerating admixture meeting the re-quirements of ASTM C 494

l 100 lb/yd³ of additional cement

During periods not defined as cold weather, but whenfreezing temperatures may occur, protect concrete sur-faces against freezing for the first 24 hr after placing.

3.4.5 Protection for structural safety - If the con-crete strength is required for structural safety, extend

COLD WEATHER CONCRETING SPECIFICATION 306.1-5

the duration of the protection period to ensure the nec-essary strength development. The strength required forformwork removal, for reshoring, or for continuedconstruction shall be as specified in the Contract Doc-uments for each type of structural member. Verifywhether the required strength has been attained by us-ing one or more of the following methods:

l ASTM C 31 (use procedures in section titled“Curing for Determining Form Removal Timeor When a Structure May be Put into Service”)

l ASTM C 803l ASTM C 873l ASTM C 900

A correlation with cylinder strength, using the specificconcrete intended for construction, is required forASTM test methods C 803 and C 900.

3.4.6 Protection deficiency - If the temperature re-quirements during the specified protection period arenot met but the concrete was prevented from freezing,continue protection until twice the deficiency of pro-tection in degree-hours is made up. Deficient degree-hours may be determined by multiplying the averagedeficiency in temperature by the number of hours thetemperature was below the values shown in Column 2of Table 3.2.1.

APPENDIX - METRIC CONVERSIONS