inspection and evaluation of concrete in 1913 facilities

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Inspection and Evaluation of Concrete in 1913 Facilities, Evanston, Illinois

Report to City of Evanston Water and Sewer Division 555 Lincoln Street Evanston, IL 60201 by John J. Roller, PE, SE Carlton A. Olson February 26, 2010 CTLGroup Project No. 262442 COA # 184-001246

Inspection and Evaluation of Concrete in 1913 Facilities Page i of ii CTLGroup Project No. 262442 February 26, 2010

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TABLE OF CONTENTS

Page

1 INTRODUCTION ...................................................................................................................1

2 REVIEW OF AVAILABLE DOCUMENTS ..............................................................................3

3 FIELD INVESTIGATION........................................................................................................3

3.1 INSPECTION OF FILTER TANKS ................................................................................3

3.1.1 Visual Inspection and Hammer Sounding of Filter Tank Concrete Surfaces ............4

3.1.2 Nondestructive Testing (NDT) of Filter Tank Concrete .............................................9

3.2 INSPECTION OF CLEARWELLS 1 AND 2.................................................................11

3.2.1 Visual Inspection and Hammer Sounding of Clearwell Concrete Surfaces.............12

3.2.2 Nondestructive Testing (NDT) of Clearwell Concrete .............................................14

3.3 INSPECTION OF PIPE GALLERY AND DEHUMIDIFICATION ROOM .....................16

4 SAMPLING, TESTING AND EXAMINATION OF CONCRETE ...........................................19

4.1 Concrete Compressive Strength Results ....................................................................20

4.2 Concrete Chloride Testing Results..............................................................................21

4.3 Microscopic (Petrographic) Examination Results........................................................22

4.3.1 Core Sample F15 ....................................................................................................22

4.3.2 Core Sample C7......................................................................................................23

5 DISCUSSION OF FINDINGS AND CONCEPTUAL REPAIR RECOMMENDATIONS........24

5.1 FILTER TANK ROOF SLABS .....................................................................................24

5.2 FILTER TANK BACK WALLS .....................................................................................25

Inspection and Evaluation of Concrete in 1913 Facilities Page ii of ii CTLGroup Project No. 262442 February 26, 2010

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5.3 FILTER TANK SIDE WALLS.......................................................................................26

5.4 CLEARWELL WALLS AND CEILING .........................................................................26

5.5 MISCELLANEOUS REPAIRS IN FILTERS AND PIPE GALLERY .............................28

5.6 PRELIMINARY COST DATA FOR CONCEPTUAL REPAIRS....................................28

Inspection and Evaluation of Concrete in 1913 Facilities Page 1 of 29 CTLGroup Project No. 262442 February 26, 2010

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INSPECTION AND EVALUATION OF CONCRETE IN 1913 FACILITIES

by

John J. Roller, P.E., S.E. 1

Carlton A. Olson 2

1 INTRODUCTION

The City of Evanston operates a water treatment facility located at 555 Lincoln Street in

Evanston, Illinois. The original portion of this facility (the West Plant) was constructed in 1913.

The 1913 facilities include six filter tanks (Filters 1 through 6), two below-grade filtered water

reservoirs (Clearwells 1 and 2), a pipe gallery, and dehumidification equipment room. A

schematic drawing identifying the locations of the 1913 facilities is shown in Fig. 1. CTLGroup

was retained by the City of Evanston to perform inspection and evaluation of the concrete

incorporated in the 1913 facilities. The scope of the inspection and evaluation program included

the following:

• Review of available documents.

• Visual inspection and limited nondestructive testing of Filters 1 through 6.

• Visual inspection of pipe gallery and dehumidification room areas.

• Visual inspection and limited nondestructive testing of Clearwells 1 and 2.

• Extraction of concrete core samples from selected areas of filters and clearwell structures.

• Laboratory testing and examination of extracted concrete core samples.

• Preparation of a written report.

1 Principal Structural Engineer, CTLGroup, 5400 Old Orchard Road, Skokie, IL 60077 2 Principal and Group Manager, CTLGroup, 5400 Old Orchard Road, Skokie, IL 60077


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This report provides a detailed description of the consulting services performed, along with

associated observations and conclusions. Recommendations for repairs and budgetary cost

estimates are also presented. The Report Supplement documents specific condition survey

observations.

Fig. 1 Schematic Drawing of 1913 Facilities.


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2 REVIEW OF AVAILABLE DOCUMENTS

CTLGroup reviewed available drawings related to the 1913 facilities. These drawings were

identified as “1915 Mechanical Record Plans,” and incorporated construction details related to

the filtered water reservoirs (clearwells), the pipe gallery (including the dehumidification

equipment room), and filter tanks. Drawings reviewed by CTLGroup included Sheets 1 through

20 of these plans.

CTLGroup also reviewed information related to chemical use history at the water treatment

plant. Historical chemical use data was provided by Mr. Kevin Lookis in an e-mail dated

January 4, 2010. Chemical compounds containing chlorides or sulfates can be detrimental to

concrete or embedded steel reinforcement if concentrations are high enough. Based on the

information provided, it is apparent that aluminum sulfate (either alone or in combination with

cationic polymer) and chlorine gas have been used for decades at the Evanston plant.

Treatment practices employed at the Evanston plant are reportedly consistent with other

Chicago-Area water treatment facilities that draw water from Lake Michigan. Testing and

examination of concrete core samples extracted from interior surfaces of clearwell and filter

structures were performed during this program to evaluate significance of chemical exposure

that has occurred to date.

3 FIELD INVESTIGATION

3.1 INSPECTION OF FILTER TANKS

The 1913 facilities include six filter tanks (Filters 1 through 6). According to available drawings,

each filter has exterior plan dimensions of 25 ft x 38 ft. The 38-ft long concrete side walls are 9-

in. thick, and are reinforced with a single layer of vertical and horizontal bars located near the

outer face. The 25-ft long concrete end walls are predominantly 12-in. thick; however, the

above-grade portion of the exterior end wall tapers from 12- to 9-in. thick within the upper 3 ft

region. The interior end wall is reinforced with a single layer of vertical and horizontal bars

located near the outer face. The exterior end wall is reinforced with two layers of vertical and

horizontal bars.

The overall depth of each filter tank is 10 ft, with the lower 3.5 feet occupied by the strainer

system and filtration media. Each filter tank is longitudinally divided into halves (east and west)

by a central 2 ft wide channel that collects wash water from a network of six gutters located on

each side. The interior concrete walls that form the sides of the channel are 6-in. thick and are


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reinforced with two layers of vertical and horizontal bars. Both channel walls have a series of

four equally-spaced large window openings near the top separated by three 18-in. wide

columns.

Each filter tank has a concrete roof slab that covers approximately 75% of the plan area. The

roof originally consisted of a 5-in.-thick concrete slab reinforced with a single layer of bars in

both longitudinal and transverse directions. Since the time of original construction, the top

surface of the roof slab of all six filter tanks has reportedly been subject to multiple

repair/rehabilitation programs. The top surface of the roof slab for Filters 1 through 6 has

reportedly undergone at least one partial-depth repair, and the addition of a supplementary

lightweight topping layer. Approximately eight years ago, a 6-ft wide strip of the lightweight

topping along the outermost edge of the roof slab for Filters 1, 3 and 5 was reportedly removed

and replaced. The roof slab for Filters 2, 4 and 6 reportedly underwent a partial-depth repair

approximately two years ago (2008) wherein the lightweight topping and the upper portion of the

slab was demolished and replaced with new concrete.

The top surface of the roof slab and the exterior above-grade portion of the south wall of Filters

1, 3 and 5 are currently exposed to weather. The top surface of the roof slab for Filters 2, 4 and

6 was recently enclosed, leaving only the exterior above-grade portion of the north wall exposed

to weather. All other filter tank wall, floor, or roof surfaces are either below grade or within the

building enclosure.

On January 12 through 14, 2010, CTLGroup performed visual inspection, hammer sounding,

and limited nondestructive testing of accessible concrete surfaces of Filters 1 through 6.

Concrete core samples were also extracted at various locations.

3.1.1 Visual Inspection and Hammer Sounding of Filter Tank Concrete Surfaces

On the interior of each filter, all wall surfaces above the filter media and the bottom surface of

the roof slab were visually examined and sounded. On the exterior, the top surface of the roof

slab and above-grade portion of the north (Filter Nos. 2, 4 and 6) or south (Filter Nos. 1, 3 and

5) walls were visually examined and sounded. Sounding involves striking the concrete surface

with a hammer and listening for audible indications of distress. Sound, undamaged concrete

will typically exhibit a distinct ring or “sharp” audible sound that is consistent with what would be

expected from impact with a hard steel tool. Concrete that has been altered or damaged will

typically exhibit an audible sound that is “dull” or hollow-sounding when struck with a metallic


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object. Observed concrete cracks and areas where hammer sounding revealed audible

indications of suspect integrity were mapped to scale on drawings. Maximum crack widths were

measured and documented where possible. Documented observations for each of the filter

tanks are provided in the Report Supplement (see F-Series sheet numbers). Significant findings

from the filter tank inspections are as follows:

1. All original interior concrete wall surfaces exhibited varying degrees of surface scaling.

2. The interior surface of the back wall exhibited ice build-up, indicating that both interior and

exterior surfaces of these walls are subject to freeze-thaw exposure during winter months.

3. Interior inspection of each filter tank revealed that a 1-to-2-in. thick layer of shotcrete has

been applied to the underside of the roof slab. It is our understanding that this shotcrete

was likely applied sometime in the 1980’s. The shotcrete layer typically extends down the

adjoining vertical walls for a distance of approximately 12 in. Varying degrees of cracking

was observed in the shotcrete layer for all six filter tanks. Cracks in the shotcrete are filled

with efflorescence (a white-colored deposit), thus preventing crack width measurement.

Localized delaminated/hollow-sounding areas were noted in five of the six filters, with

Filters 2, 4 and 6 exhibiting the greatest populations of these areas. Evidence of shotcrete

repair was also observed in these three filters. Exposed/corroded wire mesh

reinforcement was noted in the shotcrete layer for Filters 2, 3 and 5. Specific locations of

cracks and delaminated/hollow-sounding areas are shown in the reflected ceiling plans

included in the Report Supplement.

4. The west side wall of Filters 1 and 3 exhibits a horizontal crack on the interior surface.

Both cracks are very similar in location and appearance. These cracks appear to initiate at

the inside corner where the west wall intersects the back wall, and extend for a length of

approximately 25 to 28 ft. Both cracks have been repaired (filled) over a portion of the

length using a black tar-like substance, and then subsequently covered with a thin layer of

shotcrete. Where unfilled, estimates of crack widths range from 0.020 to 0.040 in. The

thin shotcrete layer has become loose or fallen off at several locations. A photograph of

the crack noted in the west side wall of Filter 2 is shown in Fig. 2.


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Fig. 2 Crack Noted in West Side Wall of Filter 2.

5. The side walls of all six filters typically exhibit one or more vertical or diagonal cracks that

generally extend from the roof slab down below the filter media. In many instances, these

cracks coincide with gutter locations. Most cracks are filled with efflorescence, thus

preventing crack width measurement. Where unfilled, estimates of crack widths range

from 0.015 to 0.025 in. A photograph of the cracks noted in the west side wall of Filter 6 is

shown in Fig. 3.

6. The interior surface of the back wall of all six filters typically exhibits multiple cracks.

These cracks are generally horizontal or diagonal. Many of the cracks intersect the interior

concrete walls that form the sides of the channel that bisects each filter tank. Most cracks

are filled with efflorescence, thus preventing crack width measurement. Where unfilled,

estimates of crack widths range from 0.015 to 0.025 in. The back wall for two of the six

filters (Filters 2 and 4) exhibited localized areas near the roof slab where hammer

sounding revealed audible indications of suspect integrity. A photograph of the cracks

noted in the back wall of Filter 2 is shown in Fig. 4.


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Fig. 3 Cracks Noted in West Side Wall of Filter 6.

Fig. 4 Cracks Noted in Back Wall of Filter 2.


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7. Wash water gutters appear to be in good condition, exhibiting no visible cracking except at

wall interfaces.

8. Localized areas exhibiting delaminated/hollow sounding and/or cracked concrete were

observed at a few locations near the interior openings of the filter tanks. These areas were

generally limited to the underside of the short elevated slab section that spans

longitudinally between the front end wall and roof slab, and to the innermost edge of the

roof slab. In some instances, previous repair attempt was evident. An example of such

distress is shown in Fig. 5.

9. Exterior above-grade portions of the back wall of all six filter tanks typically exhibit a

uniform network of fine cracks likely caused by freeze-thaw exposure. A photograph of

this typical cracking is shown in Fig. 6. All cracks are filled with efflorescence, thus

preventing crack width measurement. Several areas where hammer sounding revealed

audible indications of suspect integrity were also noted on the exterior surface of these

walls.

Fig. 5 Distress Noted at Interior Opening of Filter 3.


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Fig. 6 Typical Cracking Noted on South Wall Exterior Surface of Filter 5.

10. The exterior roof surface for Filters 1, 3 and 5 exhibits several large delaminated/hollow-

sounding areas within portions incorporating the lightweight topping. Most of these hollow-

sounding areas are adjacent to the manhole openings that penetrate the roof slab. Other

areas not incorporating the lightweight topping (the 6-ft wide strip incorporating

conventional concrete topping along the outermost edge of the roof) exhibit a network of

fine, orthogonal, regularly-spaced cracks.

11. The top roof surface for Filters 2, 4 and 6 exhibits a somewhat uniform network of random

cracks. Most cracks intersect the manhole openings that penetrate the roof slab.

3.1.2 Nondestructive Testing (NDT) of Filter Tank Concrete

Nondestructive testing (NDT) using pachometer and Impulse Response (IR) equipment was

performed in representative study areas. A pachometer is an instrument that utilizes an

electromagnetic field to locate steel elements embedded in concrete. Pachometer surveys were

performed on the north wall of Filter 4 and the south wall of Filter 3 to identify reinforcing bar

spacing and concrete cover. One representative area was selected and tested on both interior

and exterior wall surfaces of each filter. Surveys were performed within the upper tapered


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portion of the wall where thickness decreases from 12 in. to 9 in. According to available

drawings, the specified wall reinforcement consists of two layers of vertical (5/8” @ 24 in.) and

horizontal (3/8” @ 18 in.) bars. Results from the pachometer surveys indicated spacing of

reinforcement was reasonably consistent with what was specified in available drawings.

Measured concrete cover over the reinforcing bars varied considerably, ranging from as little as

3/8” to as much as 2-3/4”. Concrete cover requirements are not specified in the drawings.

Current code requirements for cast-in-place concrete exposed to weather call for minimum

concrete cover of 1-1/2 in.

The IR NDT technique involves applying a low strain impact to the concrete surface with a

hammer of a known mass, and measuring the force input and velocity response. The principal

output parameter yielded from IR testing is average mobility. The average mobility is defined as

the surface velocity responding to the impact divided by the force input [(m/s)/N x10–7]. The

mean mobility value over the 0.1-1 kHz range is directly related to the concrete modulus,

density and effective thickness. In general, presence of an internal delaminated layer,

weakened layer or cold joint, will result in an increased average mobility value. On the other

hand, a sound concrete element without distress will typically exhibit a reduced average mobility

value.

IR surveys were performed on the interior surface of the south wall of Filter 3, and on the

exterior surface of the north wall of Filter 4. As indicated by the condition survey results

provided on pages F3-D and F4-E of the Report Supplement, the south wall of Filter 3 and north

wall of Filter 4 exhibited multiple areas of concrete distress in the form of cracking and/or

audible indications of suspect integrity. For comparison, an IR survey was also performed on

the interior surface of the east wall of Filter 3, in an area where there is no evidence of concrete

distress. Results from the IR surveys indicated correlation between observed surface

conditions and corresponding average mobility readings. Average mobility readings obtained

from the east wall of Filter 3 were consistent and relatively low, indicating that the wall is sound

in the area where the survey was performed. Average mobility readings for the interior surface

of the south wall of Filter 3 and exterior surface of the north wall of Filter 4 were generally higher

and more variable, indicating the integrity of these walls has likely been compromised to various

extents due to deterioration.

In an effort to confirm the results from the IR testing, concrete cores were extracted from

selected locations within the IR survey areas. Locations of the concrete cores are identified in


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condition survey documentation given in the Report Supplement. Results from the IR testing

are provided in Table 1, along with corresponding observations documented before and after

core extraction. Photographs of the extracted cores are provided in Appendix A.

Table 1 – IR NDT Test Results and Corresponding Core Observations

Filter Test/Core Location

Concrete Surface

Condition

Average Mobility, (m/s)/N x10–7

Core I.D. Core Condition Observation

3 East Wall,

Interior Surface

No Cracks/ Sound

6.33 F3 No Cracks

3 South Wall,

Interior Surface

Cracked/ Sound 23.10 F1

Transverse cracking noted at depth of 1-1/2 in. from

surface.

3 South Wall,

Interior Surface

Cracked/ Sound 19.25 F2

Transverse cracking noted at depths of 2-1/2 in., 3-1/2 in. and 5-1/4 in. from surface.

4 North Wall,

Exterior Surface

No Cracks/ Sound

5.64 F12 No Cracks

4 North Wall,

Exterior Surface

Cracked/ Hollow 56.72 F13

Multiple transverse cracks noted within 4-1/2 in. from

surface.

4 North Wall,

Exterior Surface

Cracked/ Dull 12.54 F14 Horizontal crack noted

through full length of core.

3.2 INSPECTION OF CLEARWELLS 1 AND 2

The 1913 facilities include two filtered water reservoirs (Clearwells 1 and 2). The two clearwells

are located entirely below grade, and a portion of each supports the building that houses the six

filter tanks. According to available drawings, the northernmost clearwell (Clearwell No. 1) is

rectangular-shaped and has interior plan dimensions of approximately 87 ft x 161 ft. The

southernmost clearwell (Clearwell No. 2) is L-shaped with maximum interior plan dimensions of

approximately 67 ft x 161 ft. Both clearwells have curved (elliptical) floor and ceiling surfaces,

and floor-to-ceiling heights ranging from approximately 14 to 19 ft. The clearwell ceiling slabs

are supported by 16 in. x 16 in. or 20 in. x 20 in. concrete square columns spaced at 12.5 ft on

center. The ceiling slab thickness is 9 in. beneath the building and 6 in. elsewhere. The

exterior walls range from 18 to 36-in. thick.


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On January 21 through 25, 2010, CTLGroup performed visual inspection, sounding, and limited

nondestructive testing of accessible concrete surfaces of Clearwells 1 and 2. Concrete core

samples were also extracted at various locations.

3.2.1 Visual Inspection and Hammer Sounding of Clearwell Concrete Surfaces

On the interior of each clearwell, all wall, floor, column, and ceiling surfaces were visually

examined. On the interior of Clearwell 1, sounding of accessible wall, floor, column, and ceiling

surfaces was also performed. Observed concrete cracks and areas where hammer sounding

revealed audible indications of suspect integrity were mapped to scale on drawings. Maximum

crack widths were measured and documented where possible. Documented observations for

each of the clearwells are provided in the Report Supplement (see CW-Series sheet numbers).

Significant findings from the clearwell inspections are as follows:

1. All interior concrete wall and column surfaces exhibited varying degrees of surface

scaling. Observed scaling was noticeably more extensive in Clearwell 1 than in

Clearwell 2.

2. Approximately 25 percent of the plan area for Clearwell 1 and 50 percent of the plan

area for Clearwell 2 serves as the foundation for the building above. After draining each

clearwell, frost was observed on portions of the ceiling not directly below the building.

Based on this observation, it appears that portions of the roof slab for both clearwells

may be subject to freeze-thaw exposure during winter months. In addition, it was noted

that approximately 35 percent of the plan area for Clearwell 1 lies directly beneath a

paved area that accommodates parking and access to a loading dock. Consequently, it

appears that a portion of the roof slab for Clearwell 1 may also be exposed to de-icing

salts and traffic loading.

3. Both clearwells exhibit several vertical wall cracks that extend from floor into ceiling.

Many of these cracks appear to have occurred at joints between adjacent formwork

sections. Many of these cracks have been previously patched, and the patch material

has subsequently become cracked and delaminated. Some of these cracks are filled

with efflorescence or with vegetation, thus preventing crack width measurement. Where

unrepaired and open, estimates of crack width range from 0.035 to 0.060 in.

Representative photographs are provided in Figs 7 and 8.


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Fig. 7 Vertical Crack Noted on North Wall of Clearwell 1.

Fig. 8 Vertical Crack Noted on West Wall of Clearwell 2.


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4. Hammer sounding of accessible wall, floor and ceiling surfaces inside Clearwell 1

revealed no audible indications of suspect integrity except at locations where patches

had been applied to existing wall and/or ceiling cracks. At most locations where patches

over cracks exist, the patch material has become cracked/delaminated.

5. The north and east walls of Clearwell 1 exhibit several horizontal cracks. These cracks

typically exist along the upper half of the wall. Horizontal cracks observed at the

northeast corner of Clearwell 1 are shown in Fig. 9. Recognizing that these cracks were

observed only along the north and east walls, and that these walls are located directly

beneath the paved parking and loading dock access area, it appears that they may be

related to traffic load from above.

6. The elliptical floor and ceiling surfaces of Clearwells 1 and 2 exhibit numerous

orthogonal cracks. These cracks typically exist along the high- and low-points of the

elliptical ceiling and floor surfaces, midway between adjacent column lines. Ceiling

cracking is most prominent in areas not beneath the building. Distribution of floor

cracking was relatively uniform throughout each clearwell. Evidence of water, soil or

vegetation infiltration through ceiling cracks was observed at several locations in both

clearwells. Representative photographs are provided in Figs. 10 and 11.

7. The columns of Clearwells 1 and 2 appear to be in good condition. A few of the columns

in Clearwell 1 exhibited minor cracks near the top and localized areas of poor concrete

consolidation. Many of the columns in Clearwell 1 exhibit extensive surface scaling from

approximately mid-height to ceiling level. Column surface scaling was minimal in

Clearwell 2.

8. Exposed reinforcing steel was observed at a few localized areas in the ceiling of both

Clearwells 1 and 2, with some associated corrosion and minor concrete cracking.

3.2.2 Nondestructive Testing (NDT) of Clearwell Concrete

Nondestructive testing (NDT) using pachometer and Impulse Response (IR) equipment was

attempted in representative study areas within Clearwell 1. However, due to the degree of

concrete surface saturation inside the clearwell, NDT activities did not produce meaningful

results. Consequently, these results are not presented in this report.


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Fig. 9 Horizontal Wall Cracks Noted at Northeast Corner of Clearwell 1.

Fig. 10 Cracks Noted on Ceiling of Clearwell 1.


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Fig. 11 Cracks Noted on Ceiling of Clearwell 2.

3.3 INSPECTION OF PIPE GALLERY AND DEHUMIDIFICATION ROOM

The 1913 facilities include a pipe gallery and dehumidification equipment room located between

the filter tanks and clearwells. The pipe gallery and dehumidification equipment room have

combined interior plan dimensions of approximately 17.5 ft x 100 ft. The long side walls of the

pipe gallery are common walls to the filter tanks above and adjacent clearwells. These walls

have multiple pipe penetrations leading into the filters and clearwells. The three side walls of

the dehumidification equipment room are common walls to the adjacent clearwells.

On January 13 through 15, 2010, CTLGroup performed visual inspection and sounding of

concrete surfaces of the pipe gallery and dehumidification equipment room. Accessible wall,

floor (including stairs), column, and ceiling surfaces were examined. Observed concrete cracks

and areas where hammer sounding revealed audible indications of suspect integrity were

mapped to scale on drawings. Maximum crack widths were measured and documented where

possible. Documented observations for the pipe gallery and dehumidification equipment room

are provided in the Report Supplement (see PG-Series sheet numbers). Significant findings

from the inspection are as follows:


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1. Along the north and south walls of the pipe gallery, there are continuous horizontal

construction joints located at approximately mid-height, denoting where the front end

walls of the filter tanks above meet the exterior wall of the clearwell below. Along these

joints, there are numerous areas of efflorescence, likely resulting from moisture exuding

from the joint. A representative photograph of this condition is shown in Fig. 12.

2. Beneath the aforementioned joint, there are several vertical cracks that extend

downward to the floor surface. Five of these cracks penetrate through the entire wall

thickness, as evidenced by the existence of a crack observed at the same location on

the corresponding inside wall surface of the adjacent clearwell. Where cracks

penetrated into the adjacent clearwell, evidence of corresponding water leakage into the

pipe gallery was observed. One of these cracks measured 0.040 in. wide. A

representative photograph of this condition is shown in Fig. 13.

3. In addition to the vertical cracks noted in the pipe gallery walls, several small areas

exhibiting surface spalls with exposed reinforcing steel or where hammer sounding

revealed audible indications of suspect integrity were noted. Concrete surface spalls

were also noted along the vertical joint that separates the 1913 construction from the

adjacent next-generation construction.

4. Numerous vertical cracks were observed along the sides of the drain and filtered water

conduits that run down the middle of the pipe gallery and dehumidification equipment

room. Most of these cracks are relatively short, and have measured widths ranging from

0.005 to 0.020 in. A few of these cracks span the full height of the stacked conduits,

some of which exhibit evidence of water leakage. Numerous random cracks were

observed on the top surface of the drain conduit.

5. The underside of the stairs leading down into the pipe gallery and dehumidification

equipment room from above have a few areas exhibiting surface spalls with exposed

reinforcing steel. One such area is shown in Fig. 14. In areas where the reinforcing

steel is exposed, observed cracking of the surrounding concrete is limited. On the

topside of the stairs, diagonal cracking and localized areas exhibiting hollow sound were

noted between adjacent stair treads.


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Fig. 12 Efflorescence Noted Along Construction Joint

Fig. 13 Apparent Water leakage at Location of Vertical Thru-Wall Crack


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Fig. 14 Concrete Surface Spall and Exposed Reinforcing Steel on Underside of Stairs

6. Some random cracking and localized areas of exposed reinforcing steel were noted on

floor and ceiling surfaces. Limited hammer sounding of these surfaces revealed no

audible indications of suspect concrete integrity.

7. Concrete columns appeared to be in good condition, exhibiting little surface cracking

and no audible indications of suspect concrete integrity.

4 SAMPLING, TESTING AND EXAMINATION OF CONCRETE

Fifteen partial-depth core samples were extracted from the walls and roof slabs of the filter

tanks. Seven partial-depth core samples were extracted from the walls of Clearwell 1. Some of

these cores were used for laboratory testing and examination, which included concrete

compressive strength tests, tests to determine total chloride-ion concentration at different

depths from the surface, and microscopic (petrographic) examination to evaluate overall

concrete condition and characteristics. The remaining cores were used for general observation


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of concrete condition. Locations of all extracted core samples are shown in the condition survey

results provided in the Report Supplement. Individual core logs documenting specific

observations and conditions associated with each core sample are provided in Appendix A.

4.1 CONCRETE COMPRESSIVE STRENGTH RESULTS

Six core samples were tested in compression in accordance with ASTM Designation C 42,

“Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete.”

Three of the cores selected for compressive strength testing (Cores F2, F3 and F4) were

extracted from the interior side of the east wall of Filter 3. The remaining three cores (Cores C1,

C2 and C3) were extracted from the interior side of the north wall of Clearwell 1. Specific core

locations are shown in the condition survey results provided in the Report Supplement. Results

from the compressive strength tests are given in Table 2. Available facility drawings do not

indicate concrete compressive strength requirements. Consequently, no strength basis for

acceptability is currently available. However, it is likely that concrete design strength for the

1913 facilities would have been 3,000 psi or less.

Strength results associated with Type 1 fractures generally produce the most reliable measures

of compressive strength. Results presented in Table 2 for the Type 1 fractures are reasonably

consistent for each structure, with the filter concrete strength averaging approximately 9,000 psi

and the clearwell concrete strength averaging approximately 4,000 psi. The strengths

associated with the filter cores are consistent with what might be expected for a concrete of this

age subject to a moist environment. The strengths associated with the clearwell cores are

somewhat lower than might be expected.

Table 2 – Core Compressive Strength Test Results

Core Specimen Concrete

Compressive Strength, psi

Fracture Pattern

Filter 3 – Core F3 8,910 Type 1 (conical)

Filter 3 – Core F4 9,190 Type 1 (conical)

Filter 3 – Core F5 7,880 Type 4 (diagonal)

Clearwell 1 – Core C1 3,610 Type 1 (conical)

Clearwell 2 – Core C2 4,270 Type 1 (conical)

Clearwell 3 – Core C3 5,090 Type 4 (diagonal)


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4.2 CONCRETE CHLORIDE TESTING RESULTS

Total chloride-ion (Cl-) concentration was determined near the surface, at a depth of

approximately 1 in., and at the inner-most end of one core sample from Filter 3 and one core

sample from Clearwell 1. The core sample from Filter 3 (Core F3) was extracted from the

interior side of the east wall. The core sample from Clearwell 1 (Core C3) was extracted from

the interior side of the north wall. Excessive amounts of chloride-ion in reinforced concrete can

lead to corrosion of embedded reinforcing steel and corresponding cracking and delamination.

Recognizing that chlorine is routinely used in the water treatment process, the potential for

chloride exposure to interior concrete surfaces is inevitable. The objective of the concrete

chloride testing is to evaluate concentrations present at various depths beneath surfaces

exposed to water, and to determine if measured quantities at each depth would be considered

deleterious to reinforced concrete.

Concrete samples representing the three levels were saw-cut from each core. The thickness of

each saw-cut specimen was approximately 1/4 in. The filter tank and clearwell wall surfaces

typically had a thin layer of residue that had been deposited over time by the water. This layer

was intentionally eliminated prior to obtaining the samples used for chloride testing by cutting

and discarding the outer 1/8-in. of the core. Consequently, the sample representing “near

surface” consisted of concrete at a depth range of approximately 1/8 - 3/8 in. in from the

surface. Each of the three concrete samples obtained from each core were processed and

analyzed for total chloride concentration in accordance with ASTM Designation: C1152.

Results of chloride tests are given in Table 3.

Table 3 - Total Chloride Content Test Results

Structure Sample Depth Total Chloride Concentration, % by sample weight

Near Surface (1/8 – 3/8 in.) 0.039

Approximately 1 in. (7/8 – 1-1/8 in.) 0.045 Filter 3 Innermost End (8-3/4 in.) 0.032

Near Surface (1/8 – 3/8 in.) 0.035

Approximately 1 in. (7/8 – 1-1/8 in.) 0.040 Clearwell 1 Innermost End (8-3/4 in.) 0.037


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The American Concrete Institute (ACI) Committee 222 reports an approximate acid-soluble

(total) chloride ion threshold of 0.20 % by weight of cement in order to initiate corrosion of

embedded mild steel in concrete. For concretes with conventional strength levels, the ACI

Committee 222 threshold translates to approximately 0.03 percent acid-soluble chloride by

weight of sample. As indicated by the data in Table 3, measured acid-soluble (total) chloride

concentrations at all three levels were somewhat greater than the ACI threshold. Measured

chloride concentrations corresponding to the “innermost end” sample depth likely represent a

baseline condition for the concrete prior to introduction of any additional chloride from the

surrounding environment. Recognizing that the measured chloride concentrations at other

depths are not that different than the baseline values, chloride contribution from the water

stored inside the filter tanks and clearwells does not appear to have had a significant effect on

overall concrete chloride content. In addition, observed concrete distress does not appear to be

attributable to chloride exposure.

4.3 MICROSCOPIC (PETROGRAPHIC) EXAMINATION RESULTS

One core sample taken from the filter tanks (Core F15) and one core sample taken from a

clearwell (Core C7) was subjected to microscopic (petrographic) examination. Core F15 was

extracted from the roof slab of Filter 3. Core C7 was extracted from the north wall of Clearwell

1. As indicated in the condition survey results provided in the Report Supplement, Core F15

was removed from an area where hammer sounding revealed audible indications of suspect

integrity, and Core C7 was removed adjacent to a vertical crack.

Petrographic examination was performed on each core sample in accordance with ASTM

Designation C 856, “Standard Practice for Petrographic Examination of Hardened Concrete.”

The objective of the examination was to evaluate overall condition, identify concrete

characteristics, and identify any deleterious reactions that may have contributed to the observed

conditions. Detailed findings from the petrographic examination are given in Appendix B.

Summary observations from the petrographic examination are discussed below.

4.3.1 Core Sample F15

1. Core F15 is comprised of three different concrete layers. The outermost layer consists

of approximately 5-3/4 in. of lightweight topping. The intermediate (middle) layer

consists of approximately 2-in. of conventional concrete topping. The innermost layer is


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believed to represent a portion of the original roof slab concrete. Evidence of resinous

material (likely bonding agents) was observed at the interface between each layer.

2. The outermost lightweight topping layer of Core F15 contains a fracture at a depth of

approximately 2-3/4 in. from the surface. Examination of the fracture surface revealed

small amounts of calcium carbonate deposits. The topping layer was made with

crushed, lightweight expanded shale aggregates. The cementitious paste incorporates

portland cement and fly ash. The estimated air content of the topping layer is very high

(10 to 13 percent), and the air void system is coarse. Many voids are lined with

secondary ettringite and calcium carbonate deposits, likely indicating passage of

moisture. The top surface of the topping is carbonated to a depth of approximately 0.5

in. The bond between the lightweight topping layer and the adjacent concrete layer is

tight.

3. The intermediate (middle) concrete layer is in good condition, exhibiting no significant

cracks or microcracks. The outermost surface is irregular, and likely represents a

surface that was roughened prior to installation of the lightweight topping. The concrete

exhibits good physical paste properties and is air-entrained. The estimated air content is

3 to 4 percent. The bond between the intermediate concrete layer and the adjacent

innermost concrete layer is relatively weak.

4. The innermost concrete layer of Core F15 is in poor condition. Numerous observed

cracks and microcracks are attributed to freeze-thaw exposure. The concrete is not air-

entrained, and incorporates an estimated total air content of less than 1 percent.

Secondary ettringite and calcium carbonate deposits are abundant in the cracks, likely

indicating passage of moisture.

4.3.2 Core Sample C7

1. The outer 0.2 to 0.3 in. of Core C7 is soft and crumbly. Microscopic examination

revealed that the concrete near the outer surface has been altered by carbonation and

subsequent leaching of carbonate compounds. Conditions observed at the outer

surface are attributed to long-term exposure to a mildly-aggressive environment.

2. With the exception of the outer surface region, the concrete represented by Core C7 is in

good condition, exhibiting no visible cracks or excessive microcracks. Physical paste

properties are consistent with concrete made and placed with moderately high water-


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cement ratio. The concrete is not air-entrained, and incorporates an estimated total air

content of 1 to 2 percent. No evidence of intrinsic material defects or deleterious

chemical reactions was observed.

5 DISCUSSION OF FINDINGS AND CONCEPTUAL REPAIR RECOMMENDATIONS

Many of the documented conditions observed in the 1913 concrete facilities are judged to be

minor, having little apparent current structural or operational consequence. These conditions do

not require any specific corrective action at this time. However, there are some documented

conditions where corrective action is recommended. These conditions are identified and

discussed below, along with recommended conceptual repairs and associated preliminary cost

data.

5.1 FILTER TANK ROOF SLABS

Based on our observations and findings, it is CTLGroup’s opinion that the roof slabs of all six

filters require rehabilitation. Cores extracted from the roof slab of Filters 1, 3 and 5 indicate the

existence of in-plane cracks at various depths. The original concrete located beneath multiple

layers of supplementary topping is in very poor condition due to exposure to freeze-thaw

conditions. The outermost lightweight topping layer exhibits similar deterioration and is also in

poor condition. As a result of the observed deterioration, the structural integrity of the roof slabs

for Filters 1, 3 and 5 has likely been severely compromised. In addition, further degradation is

inevitable unless corrective action is taken.

It is our understanding that the roof slab for Filters 2, 4 and 6 recently underwent a partial-depth

repair from the top side downward. However, based on communications with City staff involved,

the implemented repair did not eliminate all of the deteriorated concrete. In addition, recent

inspection identified extensive cracking in the new concrete topping layer, and cracking and

delamination in the shotcrete layer applied to the slab soffit. Consequently, the structural

integrity of these roof slabs is also in question. Although the roof slabs for Filters 2, 4 and 6 are

no longer exposed to weather, they now serve as a functional floor surface subjected to other

loading conditions. As a result of the deteriorated concrete that likely still remains in the middle

portion of the slab, the new concrete topping and the shotcrete layer applied to the underside

are now being compromised. Further degradation of these slabs will likely occur unless

corrective action is taken.


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It is CTLGroup’s opinion that the roof slabs for Filters 1, 3 and 5 should be completely replaced

with durable air-entrained concrete. It is envisioned that this repair would be accomplished by

first shoring the existing slabs and masonry walls using the interior and exterior walls and

possibly some of the drainage gutters for support. Once properly shored, demolition and

reconstruction would be performed from the exterior.

It is CTLGroup’s opinion that partial-depth replacement of the roof slabs for Filters 2, 4 and 6

may be feasible depending upon the extent and quality of the recent restoration efforts and how

the City plans to use these slabs in the future. In order to make this determination, it will be

necessary to 1) review specific details related to the recent repair, 2) extract additional core

samples to assess effectiveness of the repair and identify how much deteriorated concrete still

exists, and 3) review anticipated loading conditions. If partial-depth replacement is deemed

feasible, it is envisioned that the repair would be executed from the underside. The repair

would likely involve demolishing the existing shotcrete layer and any residual deteriorated

concrete. Once the demolition has been completed, a new steel-reinforced shotcrete layer

would be applied. If conditions are such that partial depth replacement is judged to be not

feasible, then complete replacement of the roof slabs may be necessary.

5.2 FILTER TANK BACK WALLS

Based on our observations and findings, it is CTLGroup’s opinion that the back walls of all six

filters require rehabilitation. Cores extracted from these walls indicate the existence of

extensive concrete deterioration due to exposure to freeze-thaw conditions, most to depths

ranging from 1/3 to 1/2 of the wall thickness. These back walls carry a portion of the filter roof

slab load and, in the case of Filters 2, 4 and 6, additional load from the recently-constructed

masonry wall and roof enclosure built above. It is difficult to evaluate the load carrying capacity

of concrete damaged by cyclic freezing and thawing. To restore structural integrity and extend

the service life of the filters, deteriorated portions of the filter back walls should be removed and

replaced with durable, air-entrained concrete.

For each of the six filters, CTLGroup recommends full-thickness repairs over a portion of the

total wall height. For the south side filters (Filters 1, 3 and 5) the end wall repairs can be

accomplished at the same time the roof slab is replaced. For the north side filters (Filters 2, 4

and 6), it will be necessary to complete the roof slab rehabilitation efforts first, and then shore

the portions of the roof slab that support the recently-constructed exterior masonry wall and

roof. The filter end wall extends approximately 3 ft above grade on the south side (Filters 1, 3


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and 5) and 4 ft above grade on the north side (Filters 2, 4 and 6). It is envisioned that all above-

grade portions of the walls, and part of the below-grade portions of the wall will be removed and

replaced. Encasement of the deteriorated back walls with durable air-entrained concrete could

also be a viable alternative remedy. However, the level of effort and associated cost would

likely be comparable to full thickness replacement.

5.3 FILTER TANK SIDE WALLS

Filters 1 and 2 both have a horizontal crack in the west side wall that extends from the back wall

inward for approximately 25-30 ft. Repair attempts have apparently been made in the past;

however, the repairs are not holding up well and the cracks have extended beyond the bounds

of the previous repairs. It is CTLGroup’s opinion that further repair measures should be

implemented in the near future to keep potential water loss or infiltration to a minimum.

CTLGroup is recommending that the entire length of both cracks be repaired again using more

appropriate materials and methods. It is envisioned that these cracks will be repaired by

removing any existing old patch material, cleaning, notching or otherwise preparing the fracture

surface, and injecting an appropriate NSF-61-approved resin material.

5.4 CLEARWELL WALLS AND CEILING

During our inspection of the clearwells, several cracks were observed on floor, wall and ceiling

surfaces. Evidence of current or previous infiltration by water, soil or vegetation was observed

at most wall and ceiling crack locations. Some of the wall and ceiling cracks have been

previously patched; however, in all cases the old patch material has become cracked and

delaminated. It is our understanding that clearwell infiltration is not an acceptable condition.

Consequently, it is CTLGroup’s opinion that any proposed repair program must address the

objective of eliminating or minimizing infiltration.

Even though the clearwells are located below grade, frost was observed on portions of the

ceilings. Based on this observation, it appears that the roof slab for both clearwells may be

subject to freeze-thaw exposure during winter months. Long-term exposure to freezing and

thawing conditions could severely compromise structural integrity. At this time, the condition of

the clearwell roof slab concrete is unknown. Therefore, prior to developing or implementing a

repair program for the clearwells, it is recommended that the outer roof surface of both

clearwells be exposed at a few locations for the purpose of assessing concrete condition. This

assessment should include both visual observations and extraction of partial depth core


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samples. If further investigation indicates the structural integrity of the clearwell ceilings is not

adequate, a comprehensive rehabilitation program will have to be developed and implemented

to address this issue.

Assuming that the structural integrity of the clearwell roof slab is confirmed, it is CTLGroup’s

recommendation that repair measures to address all wall and ceiling cracks be implemented. It

is CTLgroup’s opinion that the most reliable method to repair the clearwell cracks and eliminate

infiltration would be to 1) excavate to expose all roof and wall surfaces, 2) execute full-thickness

crack repairs, and 3) apply a waterproof coating to all exterior surfaces. However, given the

highly-invasive nature of such a repair, it is questionable whether such measures would be

considered practical. Nonetheless, CTLGroup recommends that this approach be considered.

The conceptual repair offered herein focuses on repairing wall and ceiling cracks exhibiting

evidence of current or previous infiltration from the interior. It is CTLGroup’s opinion that the

repair of the clearwell cracks from the interior side cannot be accomplished with a high degree

of reliability. Due to the difficulties associated with cleaning the fracture surface, the

effectiveness of executing such repairs by injecting cracks with various moisture-insensitive

resin materials will likely be variable. Consequently, although this approach will likely be

effective in reducing infiltration for a finite period of time, it should not be viewed as a

permanent, all-encompassing solution.

It is estimated that there are approximately 300 lineal ft of wall cracks and 1700 lineal feet of

ceiling cracks inside Clearwell 1. Inside Clearwell 2, it is estimated that there are approximately

240 lineal ft of wall cracks and 750 lineal feet of ceiling cracks. It is envisioned that these

cracks will be repaired by removing any existing old patch material, cleaning, notching or

otherwise preparing the fracture surface, and injecting an appropriate NSF-61-approved resin

material.

It is our understanding that clearwell repairs would have to be executed during low-demand,

non-summer months. It is also our understanding that if the repairs are performed during early-

spring or late-fall months, internal access for up to 3 weeks could be accommodated. The time

frame required to repair all the cracks exhibiting evidence of current or previous infiltration will

depend on several factors, and cannot be accurately quantified at this time. Consequently, a

prioritized approach should be implemented which would initially focus on those cracks believed

to be of greatest concern (i.e., cracks exhibiting evidence of current infiltration). Each clearwell

could be addressed separately. In the event that all crack repairs cannot be made within the


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designated access period, subsequent access periods would need to be scheduled to complete

the work.

5.5 MISCELLANEOUS REPAIRS IN FILTERS AND PIPE GALLERY

In addition to the aforementioned conditions, there were several localized areas in the filter

tanks and pipe gallery where patch repairs are recommended. Specifically, areas where

hammer sounding revealed audible indications of delamination and areas exhibiting spalled

concrete with exposed reinforcing steel should be addressed. It is also recommended that

cracks in the pipe gallery with associated water infiltration be repaired unless it can be shown

that the infiltration is eliminated through execution of crack repairs in the clearwells. It is

envisioned that the patch repairs will be performed by removing any existing distressed

concrete, cleaning, preparing the fracture surface, and applying an appropriate repair material.

It is envisioned that pipe gallery cracks will be repaired by removing any existing old patch

material, cleaning, notching or otherwise preparing the fracture surface, and injecting an

appropriate NSF-61-approved resin material.

5.6 PRELIMINARY COST DATA FOR CONCEPTUAL REPAIRS

Preliminary cost data associated with each of the recommended conceptual repairs is provided

in Table 4. The data contained in Table 4 represent order-of-magnitude estimates of contractor

costs only. These data do not include allowances for refinement of repair concepts, design of

the actual repair to be implemented, development of details and specifications needed to

execute the repairs, administrative costs, or various unforeseen circumstances that may be

associated with execution of the work. In addition, no allowances have been included for

investigating the integrity of the clearwell roof slabs or any potential repairs that may be needed.

Estimated cost for roof slab repair for Filters 2, 4 and 6 is based on an assumed repair depth of

3 in. Estimated costs for crack repair inside the clearwells are based on an assumed production

rate of 130 lin. ft per day using a six-man crew, and include allowance for confined space safety

monitoring. Based on the assumed production rate, it would take approximately 15 days to

repair the cracks in Clearwell 1 and 8 days to repair the cracks in Clearwell 2. It should be

noted that the actual production rate for crack repair will likely depend on several factors

including conditions of access, interior ambient temperature, humidity levels, extent of water

infiltration through cracks, and type of repair material used. It is envisioned that the crack repair

activities inside each clearwell will be prioritized, and will focus initially on those cracks


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exhibiting evidence of current infiltration by water, soil or vegetation. In the event that all cracks

cannot be repaired within the designated time allotment, then addition repair intervals will need

to be scheduled.

Table 4 – Preliminary Cost Data for Conceptual Repairs

Conceptual Repair Approximate Contractor Cost

Replace Filter Tank Roof Slabs (Filters 1, 3 and 5)

$240,000

Repair Filter Tank Roof Slabs (Filters 2, 4 and 6)

$200,000

Repair Filter Tank Back Walls (Filters 1 thru 6)

$260,000

Repair Cracks in Filter Tank Side Walls (Filters 1 and 2)

$10,000

Repair Cracks in Walls and Ceiling of Clearwell 1

$160,000

Repair Cracks in Walls and Ceiling of Clearwell 2

$80,000

Miscellaneous $20,000

TOTAL $970,000

Inspection and Evaluation of Concrete in 1913 Facilities Page A1 of A1 CTLGroup Project No. 262442 February 26, 2010

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APPENDIX A

Core Logs

Evaluation of Concrete in 1913 Facilities CTL Project No. 262442

Concrete Core Sample: F-1 EVALUATION SUMMARY

LOCATION: Filter 3, South (Back) Wall, Interior Date: January 14, 2009

DIMENSIONS: L = 6-1/2 in. D = 3-3/4 in.

REINFORCEMENT: None observed.

COMMENTS: Core extracted by CTLGroup for examination and/or testing.

CRACKING: None other than where fracture was observed.

MACROSCOPICAL OBSERVATIONS: Core extracted in two pieces. Concrete fracture exists approximately 1-1/2 in. from the exposed surface. Fracture passes through and around coarse aggregate. White secondary deposits observed on surface at fracture. Bottom fracture surface passes around coarse aggregate.

View of Core F-1. (Exposed Surface at Left Side)



LOCATION: Filter 3, South (Back) Wall, Interior Date: January 14, 2009




CRACKING: Two cracks observed; both parallel to top surface. One is approximately 1-1/2 in. long and 2.5 in. in from exposed surface; the other is 1-1/4 in. long and 3.5 in. in from exposed surface.

MACROSCOPICAL OBSERVATIONS: Core extracted in two pieces. Concrete fracture observed approximately 5-1/4 in. from exposed surface. Fracture passes through coarse aggregate. White secondary deposits observed on fracture surface. Bottom fracture surface passes around coarse aggregate. White secondary deposits visible on bottom fracture surface of core.




LOCATION: Filter 3, East Wall, Interior Date: January 14, 2009




CRACKING: None observed.

MACROSCOPICAL OBSERVATIONS: Core extracted in one piece. Bottom break passes through coarse aggregate.









MACROSCOPICAL OBSERVATIONS: Core extracted in one piece. Bottom break passes through coarse aggregate. White secondary deposits observed on bottom fracture surface.









MACROSCOPICAL OBSERVATIONS: Core extracted in one piece. Bottom break occurs around coarse aggregate.

View of Core F-5. (Exposed Surface at Right Side)



LOCATION: Filter 3, South (Back) Wall, Exterior Date: January 14, 2009

DIMENSIONS: L = 6 in. D = 3-3/4 in.



CRACKING: Several cracks observed parallel to exposed surface. Cracks located within 2 inches of exposed surface.

MACROSCOPICAL OBSERVATIONS: Core extracted in one piece. Bottom break passes through and around coarse aggregate. White secondary deposits observed on bottom fracture surface and exposed (outer) surface.




LOCATION: Filter 1, South (Back) Wall, Exterior, Delaminated area Date: January 14, 2009




CRACKING: Several cracks observed parallel to exposed surface. Cracks located within 2-1/2 inches of exposed surface. Some cracks as wide as 1 mm at the surface.

MACROSCOPICAL OBSERVATIONS: Outer (exposed) surface of core (approximately 1 inch) crumbled during coring. Bottom break passes through and around coarse aggregate. White secondary deposits observed on bottom fracture surface.




LOCATION: Filter 1, Roof Slab, Exterior, Delaminated area Date: January 14, 2009


REINFORCEMENT: Wire reinforcement observed at interface between original slab concrete and initial topping layer.


CRACKING: Several cracks observed parallel to top (exposed) surface. Cracks occur primarily in outer 3 in. of 4-1/2 in. thick lightweight topping layer. Some cracks observed in concrete beneath topping, parallel to top surface.

MACROSCOPICAL OBSERVATIONS: Core extracted in two pieces. Core incorporates two distinct layers; a 4-1/2 in. thick lightweight topping layer; and a 2 in. thick mesh-reinforced concrete topping layer. Fracture observed approximately 4-1/2 in. from exposed surface (at interface between lightweight topping layer and concrete topping). Poor consolidation noted at bottom of lightweight topping layer. Fracture passes around aggregate.Bottom break occurs through and around coarse aggregate. A brownish-colored residue exists on both the intermediate and bottom fracture surfaces, and likely denotes use of some kind of bonding agent applied at the interfaces between the original roof slab concrete and concrete topping layer,and between the concrete topping layer and lightweight topping layer.








CRACKING: Several cracks observed parallel to top (exposed) surface. Cracks occur primarily in outer 4 in. of the 6-in. thick lightweight topping layer.

MACROSCOPICAL OBSERVATIONS: Core extracted in four separate pieces. Core incorporates three distinct layers; a 6-in. thick lightweight topping layer; a 1-1/2 in. thick mesh-reinforced concrete topping layer; and a 1/2 in. thick concrete layer (believed to be the original roof slab concrete). A thin line can be seen at the interface between the three distinct material layers, and likely denotes the use of some kind of bonding agent. Fractures observed in the lightweight topping at three locations. Two of the fractures are at depths of roughly 1-1/2 and 3 inches from the top (exposed surface). White secondary deposits were observed on a portion of both of these fracture surfaces. The third fracture is located at a depth of approximately 5-3/4 in. (near the interface between the lightweight topping and concrete topping). Bottom break occurs around coarse aggregate. White secondary deposits were observed on the bottom fracture surface.




LOCATION: Filter 3, Roof Slab, Exterior Date: January 14, 2009




CRACKING: Cracking observed at interface between original roof slab concrete and concrete topping layer.

MACROSCOPICAL OBSERVATIONS: Core extracted in two pieces. Core incorporates three distinct layers; a 5-3/4 in. thick lightweight topping layer; a 2 in. thick mesh-reinforced concrete topping layer; and a 1/4 in. thick concrete layer (believed to be the original roof slab concrete). A thin line can be seen at the interface between the lightweight topping and concrete topping layers, and likely denotes the use of some kind of bonding agent. Fracture observed in the lightweight topping at a depth of approximately 4-1/4 inches from the top (exposed surface). Fracture passes through and around aggregate. Bottom fracture occurred near interface between original roof slab concrete and concrete topping layer. Fracture passesthrough and around aggregate. White secondary deposits observed on bottom fracture surface.








CRACKING: Several cracks observed parallel to top (exposed) surface. Cracks occur primarily in outer 4 in. of the 5-1/4 in. thick lightweight topping layer.

MACROSCOPICAL OBSERVATIONS: Core extracted in two pieces. Core incorporates two distinct layers; a 5-1/4 in. thick lightweight topping layer; and a 1-3/4 in. thick concrete topping layer. A light-colored line can be seen at the interface between the two layers, and likely denotes the use of some kind of bonding agent. Fracture observed in the lightweight topping at a depth of approximately 1-1/4 inches from the top (exposed surface). Fracture passes around aggregate, and material adjacent to fracture exhibits extensive cracking. Bottom break occurs around coarse aggregate. A brownish-colored residue exists on the bottom fracture surface, and likely denotes use of some kind of bonding agent applied at the interface between the original roof slab concrete and concrete topping layer.




LOCATION: Filter 4, North (Back) Wall, Exterior Date: January 14, 2009





MACROSCOPICAL OBSERVATIONS: Core extracted in one piece. Bottom fracture passes through and around coarse aggregate. White secondary deposits observed on bottom fracture surface.




LOCATION: Filter 4, North (Back) Wall, Exterior, Delaminated area Date: January 14, 2009




CRACKING: Several cracks observed parallel to exposed surface. Cracks located within 4-1/2 in. of exposed surface.

MACROSCOPICAL OBSERVATIONS: Core extracted in two pieces. Fracture between the two segments passes through and around coarse aggregate. Bottom break also passes through and around coarse aggregate. White secondary deposits observed on both intermediate and bottom fracture surfaces.




LOCATION: Filter 4, North (Back) Wall, Exterior Date: January 14, 2009




CRACKING: A few coarse aggregate exhibit fine random cracks. A horizontal crack exists across the exterior (exposed) surface of the core. This fine crack can be traced along the sides of the core, and appears to extend to the bottom fracture surface.

MACROSCOPICAL OBSERVATIONS: Core extracted in one piece. Bottom break passes through coarse aggregate. White secondary deposits observed on bottom fracture surface.






REINFORCEMENT: Wire reinforcement observed at interface between lightweight topping and concrete topping layers.


CRACKING: Several cracks observed in innermost concrete layer (believed to be original roof slab concrete). Cracks occur parallel to top (exposed)/bottom break surfaces.

MACROSCOPICAL OBSERVATIONS: Core extracted in four pieces. Core incorporates three distinct layers; a 5-3/4 in. thick lightweight topping layer; a 2 in. thick concrete topping layer; and a 3-1/4 in. thick concrete layer (believed to be the original roof slab concrete). A thin line can be seen at the interface between the three distinct material layers, and likely denotes the use of some kind of bonding agent. Fracture observed in the lightweight topping at a depth of approximately 2-3/4 inches from the top (exposed) surface. Fracture passes through and around aggregate. Fractures observed in innermost concrete layer at depths of approximately 8-1/2 and 9-1/2 inches from the top (exposed) surface. Both fractures pass through and around coarse aggregate. Bottom break passes through and around coarse aggregate. White secondary deposits observed on intermediate and bottom fracture surfaces of the innermost concrete layer.



Concrete Core Sample: C-1 EVALUATION SUMMARY

LOCATION: North wall of Clearwell 1, 53-1/2 in. up from floor slab Date: January 22, 2009





MACROSCOPICAL OBSERVATIONS: Core extracted in one piece. Bottom break occurs around coarse aggregate.

View of Core C-1. (Exposed Surface at Left Side)



LOCATION: North wall of Clearwell 1, 37 in. up from floor slab Date: January 22, 2009

DIMENSIONS: L = 10-3/4 in. D = 3-3/4 in. REINFORCEMENT: None observed.







LOCATION: North wall of Clearwell 1, 37 in. up from floor slab Date: January 22, 2009








LOCATION: West wall of Clearwell 1, 41 in. up from floor slab Date: January 22, 2009




MACROSCOPICAL OBSERVATIONS: Core extracted in one piece. Bottom break passes through and around coarse aggregate.




LOCATION: South wall of Clearwell 1, 55-1/2 in. up from floor slab Date: January 22, 2009




MACROSCOPICAL OBSERVATIONS: Core extracted in one piece. Bottom break passes through and around coarse aggregate.




LOCATION: East wall of Clearwell 1, 56 in. up from floor slab Date: January 22, 2009

DIMENSIONS: L = 11 in. D = 3-3/4 in. REINFORCEMENT: None observed.



MACROSCOPICAL OBSERVATIONS: Core extracted in one piece. Break at bottom of core occurs mostly around coarse aggregate.




LOCATION: North wall of Clearwell 1, 60-1/2 in. up from floor slab Date: January 22, 2009



CRACKING: Crack observed that passes through coarse aggregate;

approximately 2 inches in length; crack is roughly parallel to top surface

and is located at a depth of approximately 2 inches from exposed surface.

MACROSCOPICAL OBSERVATIONS: Core extracted in one piece. Bottom break occurs mostly around coarse aggregate.


Inspection and Evaluation of Concrete in 1913 Facilities Page B1 of B1 CTLGroup Project No. 262442 February 26, 2010

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APPENDIX B

Microscopic (Petrograpic) Examination Data

Report for City of Evanston, Water and Sewer Division Project Number 262442 Petrographic Examination of Concrete Cores – Evaluation of Concrete in 1913 Facilities, Evanston, Illinois February 24, 2010 Submitted by: Sang Y. Lee COA # 184-001246 5400 Old Orchard Road Skokie, Illinois 60077-1030 (847) 965-7500 9030 Red Branch Road, Suite 110 Columbia, Maryland 21045 www.CTLGroup.com

Copy No. 1

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Corporate Office: 5400 Old Orchard Road Skokie, Illinois 60077-1030 Phone: 847-965-7500 Fax: 847-965-6541 Washington D.C. Office: 9030 Red Branch Road, Suite 110 Columbia, Maryland 21045-2003 Phone: 410-997-0400 Fax: 410-997-8480

CTLGroup is a registered d/b/a of Construction Technology Laboratories, Inc.

REPORT OF PETROGRAPHIC EXAMINATION

Date: February 17, 2010

CTLGroup Project No.: 262442

Petrographic Examination of Concrete Cores – Evaluation of Concrete in 1913 Facilities, Evanston, Illinois

Two concrete cores (Figs. 1 and 2) were received on January 29, 2009 from Mr. John Roller,

Principal Structural Engineer of CTLGroup. The cores were extracted by CTLGroup for

examination. Core identification and locations are summarized in Table 1.

TABLE 1 CORE IDENTIFICATION AND LOCATIONS

Core ID Location Comments

C-7 North wall of Clearwell 1, 60.6 in. up from floor slab Core extracted in one piece.

F-15 Filter 3, Roof slab, exterior, delaminated area

Core extracted in four pieces. Core incorporates three distinct layers; a 5.7 in. thick lightweight topping layer, a 2 in. thick concrete topping layer, and a 3.3 in. thick concrete layer (believed to the base roof slab concrete). A fracture was observed in the lightweight topping at a depth of approximately 2.8 in. from the top surface. Fractures were observed in the base concrete at depths of approximately 8.5 and 9.5 in. from the top surface.

Petrographic Examination (ASTM C 856) was requested to evaluate general quality and

condition, and to describe general characteristics of the concrete represented by the cores.

FINDINGS

Main findings of petrographic examination are described below. Additional information is

provided in the attached figure pages and data sheets.

Core C-7 (Core from North Wall of Clearwell 1)

The outer approximately 0.2 to 0.3 in. of the concrete is soft and crumbly (Figs. 1a and 3).

Microscopical examination reveals that the soft, carbonated surface paste (Fig. 4) and some of

City of Evanston Purchasing Division Page 3 of 18 Evaluation of Concrete in 1913 Facilities February 17, 2010 CTLGroup Project No. 262442

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the underlying harder non-carbonated paste has been partially leached of soluble constituents,

such as calcium hydroxide. Additionally, the outer approximately 0.1 to 0.2 in. of the carbonated

surface paste zone is partially leached of calcium carbonate (Fig. 5). The softening and

apparent leaching of the surface concrete, particularly carbonate compounds from the

carbonated paste, suggests that the concrete may have been exposed to an aggressive

solution. This chemical attack was probably mild, but slowly progressive. Such mild attack of

carbonate compounds has been known to occur in concrete exposed to slightly acidic water

(i.e., carbonic acid attack), soft water, and in some cases, certain organic or vegetative growth

(certain bacteria, algae, etc.).

Apart from the deteriorated outer surface region, the concrete is in generally good condition. No

visible cracks or excessive microcracks are observed in the body of the concrete. Relatively

small amounts of clear to milky alkali-silica reaction (ASR) gel deposits line a few voids, which is

not considered deleterious (no distress is associated with the occurrence of the gel deposits).

The concrete contains siliceous and calcareous aggregates in a hardened portland cement

paste. The hardened paste in the core body is moderately soft and somewhat absorptive.

Paste-aggregate bond is moderately weak. These observed physical paste properties are

generally consistent with concrete made and placed with moderately high water-cement ratio.

The concrete is not air entrained, and the estimated total air content is 1 to 2%. Depth of

carbonation is approximately 0.3 to 0.4 in. from the outer surface based on pH indicator

(phenolphthalein) test (Fig. 4).

Core F-15 (Core from Roof Slab)

The core consists of lightweight topping (5.6 to 5.7 in. thick), concrete topping (1.9 to 2.1 in.

thick), and base concrete (3 to 3.6 in., partial thickness, Figs. 6 and 7). A gray and a yellowish

gray resinous material (likely bonding agents) are observed at the interface between the two

topping layers, and the interface between the concrete topping and the base concrete,

respectively.

Lightweight Topping: The lightweight topping exhibits a sub-horizontal crack at a depth of 2.3

to 2.8 in. from the top surface. A few sub-horizontal to oblique microcracks are also observed

near the crack (Fig. 8). These observed cracks and microcracks pass through aggregate

particles. The topping was split during sample preparation (cutting) along one of the microcracks

located at a depth of approximately 3 to 3.5 in. from the top surface. Apart from these localized


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crack and microcracks, the lightweight topping is generally sound and in good condition with no

visible cracks and excessive microcracks. Based on petrographic examination, these localized

crack and microcracks are not related to any deleterious chemical reactions within the concrete.

The paste along the crack walls exhibits no carbonation. Small amounts of white deposits

(mostly calcium carbonate) are locally observed in the crack.

The topping contains crushed lightweight aggregates (expanded shale) in a hardened

cementitious paste consisting of portland cement and fly ash. Aggregate particles visually

appear evenly graded to an observed top size of 0.35 in. (9 mm), and uniformly distributed

throughout the body. The topping exhibits relatively good physical paste properties. The

hardened paste is relatively hard and dense (water droplets applied to fresh fractures are slowly

absorbed by the paste). Paste-aggregate bond is tight.

The topping appears to be air-entrained, and the estimated total air content is 10 to 13%. The

overall air-void system is relatively coarse (air voids coarser than 0.04 in. are abundant). Many

voids are lined with secondary ettringite and lesser calcium carbonate deposits. Presence of

these deposits in voids is not considered deleterious, and typically indicates abundance of

moisture within the topping. Depth of carbonation is approximately 0.5 to 0.6 in. from the top

surface based on pH indicator (phenolphthalein) test (Fig. 7). The bonding between the

lightweight topping and the underlying concrete topping is tight (the topping layers do not split

along the interface when hit with a hammer).

Concrete Topping: The topping concrete is in good condition. No significant distress (cracks or

excessive microcracks) or deleterious chemical reactions are observed. Trace amounts of clear

to milky white ASR gel deposits line a few voids, which is not considered deleterious (no

distress is associated with the observed gel deposits).

The topping contains calcareous and siliceous gravel coarse aggregate and sand fine

aggregate in a hardened portland cement paste. The aggregate particles visually appear evenly

graded to an observed top size of 0.4 in., and uniformly distributed throughout the body of the

concrete. The concrete exhibits good physical paste properties. The hardened paste is relatively

hard and very dense. Water droplets applied to freshly fractured surfaces are very slowly

absorbed or slightly bead instead of being spread and absorbed by the paste. The concrete is

air entrained, and estimated total air content is 3 to 4%.


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Bonding between the concrete topping and the underlying base concrete is relatively weak. The

resinous bonding agent is locally separated from the underlying base concrete. The bonding

agent is stained yellowish brown, and locally somewhat soft (likely indication of deterioration).

Base Concrete: The concrete is in poor condition. Narrowly-spaced, sub-horizontal cracks and

microcracks are observed through the depth (partial depth), passing through and around

aggregate particles (Fig. 9). Based on petrographic examination, these observed cracks and

microcracks are mainly attributed to damage caused by cyclic freezing and thawing of non-air-

entrained concrete while critically saturated with water. The concrete is not air entrained with the

estimated total air content less than 1% (Fig. 10).

Relatively small amounts of ASR gel deposits are locally observed in a few cracks and voids.

These gel deposits are judged to be secondary deposits filled into the pre-existing freeze-thaw

cracks and voids rather than contributing to the occurrence of the cracking based on lack of

randomly-oriented cracks and microcracks extending out of any reacting aggregate particles.

The base concrete contains siliceous and calcareous coarse and fine aggregates in a hardened

portland cement paste. The aggregate particles visually appear evenly graded to an observed

top size of 0.8 in., and uniformly distributed throughout the body of the concrete. The hardened

concrete paste in the intact areas away from the cracks is moderately hard and fairly dense.

The paste along the cracks is locally softer and more absorptive. Secondary ettringite and

calcium carbonate deposits are abundant in the cracks, indicating abundance of moisture within

the concrete, and possible infiltration and migration of moisture along the cracks.

METHODS OF TEST

Petrographic examination of the provided cores was performed in accordance with ASTM

C 856-04, "Standard Practice for Petrographic Examination of Hardened Concrete." The cores

were visually inspected and photographed as received. The distressed (cracked) portion of Core

F-15 was applied with epoxy to preserve as-received condition and to prevent damage during

sample preparation. After the epoxy hardened, each core was cut half longitudinally and one of

the resulting sides of the slice was ground (lapped) to produce a smooth, flat, semi-polished

surface. Lapped and freshly broken surfaces of the cores were examined using a

stereomicroscope at magnifications up to 45X. For thin-section study, small rectangular blocks

were cut from the top surface portion of Core C-7, and in the body of lightweight topping and


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from near the boundary between the concrete topping and the base concrete in Core F-15. One

side of each block was lapped to produce a smooth, flat surface. The blocks were cleaned and

dried, and the prepared surfaces were mounted on separate ground glass microscope slides

with epoxy resin. After the epoxy hardened, the thickness of the mounted blocks was reduced to

approximately 20 μm (0.0008 in.). The resulting thin sections were examined using a polarized-

light (petrographic) microscope at magnifications up to 400X to study aggregate and paste

mineralogy and microstructure.

Estimated water-cement (w/c), when reported, is based on observed concrete and paste

properties including, but not limited to: 1) relative amounts of residual (unhydrated and partially

hydrated) portland cement clinker particles, 2) amount and size of calcium hydroxide crystals, 3)

paste hardness, color, and luster, 4) paste-aggregate bond, and 5) relative absorbency of paste

as indicated by the readiness of a freshly fractured surface to absorb applied water droplets.

These techniques have been widely used by industry professionals to estimate w/c.

Depth and pattern of paste carbonation was determined by application of a pH indicator solution

(phenolphthalein) to freshly cut and fractured concrete surfaces. The solution imparts a deep

magenta stain to high pH, non-carbonated paste.

Sang Y. Lee, Ph.D. Senior Microscopist Microscopy Group SYL/lsy Notes: 1. Results refer specifically to the samples submitted. 2. This report may not be reproduced except in its entirety. 3. The samples will be retained for 30 days, after which they will be discarded unless we hear

otherwise from you.


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1a. Outer surface.

1b. Side view. Outer surface is to the left.

Fig. 1 Core C-7 as received for examination. Scale is marked in inches.


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2a. Top surface.

2b. Side view. Top surface is to the left. Arrows designate fractures occurred during coring.

Fig. 2 Core F-15 as received for examination. Scale is marked in inches.

Top surface


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Fig. 3 Cut and lapped cross-section of Core C-7, showing general appearance of concrete in the core. Scale is marked in inches.

Fig. 4 Saw-cut cross-section of Core C-7, to which pH indicator (phenolphthalein) solution has been applied. The outer surface region exhibiting no color change is carbonated, and the area in the core body appearing magenta is not carbonated. Scale is marked in inches.

Carbonated paste

Outer surface

Soft and crumbly paste

Outer surface


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5a. Plane polarized light.

5b. Same field of view, but in cross-polarized light.

Fig. 5 Thin-section photomicrographs showing deteriorated outer surface region of Core C-7. Calcium carbonate is locally leached from the deteriorated and carbonated surface paste zone.

Out

er S

urfa

ce

Deteriorated paste

Out

er S

urfa

ce

Leaching of calcium carbonate from carbonated paste

Outer surface


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Fig. 6 Cut and lapped cross-section of Core F-15 showing topping layers and base concrete. Top surface is up. Scale is marked in inches.

Fig. 7 Saw-cut cross-section of Core F-15, to which pH indicator (phenolphthalein) solution has been applied. The top surface region exhibiting no color change is carbonated, and the area in the core body appearing magenta is not carbonated. Top surface is up. Scale is marked in inches.

Lightweight topping

Concrete topping

Base concrete

Lightweight topping

Concrete topping

Base concrete

Carbonated paste


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Fig. 8 Image showing lightweight topping in Core F-15. The red arrow designates a crack observed in the core as received. The yellow arrows designate a crack that occurred during sample preparation in laboratory. Scale is marked in inches.

Fig. 9 Image showing the concrete topping and the base concrete in Core F-15. The concrete topping exhibits no visible cracks. The base concrete exhibits closely-spaced sub-horizontal cracks (the cracks are traced with a black pen to highlight).

Concrete topping

Base concrete

Fig. 10


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Fig. 10 Stereomicroscope image showing the area designated by the red box in Fig. 9. Lack of small, spherical voids at the lapped surface indicate that the base concrete in Core F-15 was not air entrained. Scale increments are 0.04 in.


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PETROGRAPHIC EXAMINATION OF HARDENED CONCRETE, ASTM C 856

STRUCTURE: Concrete wall DATE RECEIVED: January 29, 2009

LOCATION: Evanston, Illinois EXAMINED BY: Sang Lee

SAMPLE

Client Identification: C-7.

CTLGroup Identification: 2508001.

Dimensions: Core diameter = 3.7 in. (94 mm), core length = approximately 10.5 to 10.7 in. (267 to 272 mm); partial wall thickness.

Outer Surface: The intact portion of the surface is even and paste-rich. The surface is locally irregular and deteriorated with exposed aggregate particles to a depth of approximately 0.2 in. (5 mm). The concrete at the surface is soft and locally crumbly.

Bottom Surface: Irregular, rough fractured surface.

Cracks, Joints, Large Voids: No visible cracks, joints, or large voids are observed.

Reinforcement: No reinforcement is observed in the core submitted.

AGGREGATES

Coarse: Siliceous and calcareous rocks consisting mainly of limestone, dolomitic limestone, coarse to medium-grained granitic and metamorphic rocks, sandstone, fine-grained sedimentary rocks, and chert.

Fine: Siliceous and calcareous sand consisting of quartz, feldspar, limestone, various igneous rocks, quartzite, fine-grained sedimentary rocks, and chert with small amounts of other rocks and minerals.

Gradation & Top Size: Visually appears evenly graded to an observed top size of 1.3 in. (33 mm).

Shape, Texture, Distribution: Both coarse and fine aggregate particles are mostly rounded to subangular and equant to oblong with smooth to slightly rough surface texture; uniformly distributed.

PASTE

Color: Light buff gray in the top approximately 0.2 to 0.3 in. (5 to 8 mm), and light gray in the remaining portion of the core body.

Hardness: Soft and crumbly in the top approximately 0.2 to 0.3 in. (5 to 8 mm); moderately soft in the remaining body portion of the core.

Luster: Dull.


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Paste-Aggregate Bond: Moderately weak; fresh fractures pass around many coarse aggregate particles.

Air Content: Approximately 1 to 2%; not air entrained.

Depth of Carbonation: Approximately 0.3 to 0.4 in. (8 to 10 mm) from the top surface; locally deeper along microcracks. The calcium carbonate in the carbonated paste zone is leached in the top approximately 0.1 to 0.2 in. (3 to 5 mm).

Calcium Hydroxide*: Rarely observed at the examined thin-section location; possibly leached.

Residual Portland Cement Clinker Particles*: Almost completely hydrated; relicts of relatively coarse, hydrated portland cement particles are observed.

Supplementary Cementitious Materials*: None observed.

Secondary Deposits: Secondary calcium carbonate (calcite) deposits line some voids in the outer approximately 0.2 to 0.3 in. (5 to 8 mm) of the core. Secondary ettringite deposits line many voids in the body of the core. Clear to milky white, alkali-silica reaction gel deposits line a few voids; no distress (cracks or excessive microcracks) are associated with the observed gel deposits.

MICROCRACKING: Randomly oriented, discontinuous microcracks are occasionally observed in the core body; these microcracks are not related to any deleterious chemical reactions within the concrete.

ESTIMATED WATER-CEMENT RATIO: Moderately high based on the observed physical paste properties. Estimation is speculative due to apparent evidence of continued cement hydration.

MISCELLANEOUS: The hardened paste is highly absorptive in the outer approximately 0.2 to 0.3 in. (5 to 8 mm). The paste in the remaining core body is somewhat absorptive.

_____________________ *percent by volume of paste


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PETROGRAPHIC EXAMINATION OF HARDENED CONCRETE, ASTM C 856

STRUCTURE: Concrete roof slab DATE RECEIVED: January 29, 2009

LOCATION: Evanston, Illinois EXAMINED BY: Sang Lee

SAMPLE

Client Identification: F-15

CTLGroup Identification: 2508002.

Dimensions: Core diameter = 4.2 in. (107 mm), core length = approximately 10.6 to 11 in. (269 to 279 mm); partial roof slab thickness. The core consists of three layers; (1) 5.6 to 5.7-in. (142 to 145-mm) thick lightweight topping, (2) 1.9 to 2.1-in. (48 to 53- mm) thick concrete topping, and (3) 3 to 3.6-in. (76 to 91-mm) thick base concrete. A gray resinous material (likely bonding agent) is observed at the interface between two topping layers. A yellowish gray resinous material (likely bonding agent) is observed at the interface between the concrete topping and the base concrete.

Top Surface: Even, somewhat rough surface with partially exposed sand particles.

Bottom Surface: Irregular, rough fractured surface.

Joints, Large Voids: No joints or large voids are observed.

Reinforcement: Steel wires (0.23 in. or 6 mm diameter) or a wire mesh are embedded in the lightweight topping at a depth of 5.1 to 5.3 in. (130 to 135 mm) below the top surface. No steel reinforcement is observed either in the concrete topping or the base concrete in the submitted core.

LIGHTWEIGHT TOPPING

The topping contains crushed lightweight aggregates (expanded shale) in a hardened cementitious paste consisting of portland cement and fly ash. Aggregate particles visually appear evenly graded to an observed top size of 0.35 in. (9 mm), and uniformly distributed throughout the body. The hardened paste is relatively hard and dense (water droplets applied to fresh fractures are slowly absorbed by the paste). Paste-aggregate bond is tight.

The concrete appears to be air entrained, and the estimated total air content is 10 to 13%. Overall air-void system is relatively coarse (air voids coarser than 0.04 in. or 1 mm are abundant). Many voids are lined with secondary ettringite and calcium carbonate deposits. Similar calcium carbonate deposits are locally observed in the observed crack. Depth of carbonation is approximately 0.5 to 0.6 in. (13 to 15 mm) from the top surface based on pH indicator (phenolphthalein) test.

A sub-horizontal crack is observed at a depth of 2.3 to 2.8 in. (58 to 71 mm) from the top surface. A few sub-horizontal microcracks are observed near the crack. These observed cracks and microcracks pass through aggregate particles. The topping was split during sample preparation (cutting) along a microcrack located at a depth of approximately 3 to 3.5 in. (76 to 89 mm) from the top surface. Apart from these localized crack and microcracks, the


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lightweight topping is generally sound with no visible cracks and excessive microcracks. The lightweight topping is tightly bonded to the underlying concrete topping.

CONCRETE TOPPING

The concrete topping contains calcareous and siliceous gravel coarse aggregate and sand fine aggregate in a hardened portland cement paste. The aggregate particles visually appear evenly graded to an observed top size of 0.4 in. (10 mm), and uniformly distributed throughout the body of the concrete. The hardened paste is relatively hard and very dense. Water droplets applied to fresh fracture are very slowly absorbed by the paste or locally slightly bead instead of being spread and absorbed by the paste. The concrete is air entrained, and estimated total air content is 3 to 4%; the entrained air voids are locally somewhat widely-spaced.

No visible cracks are observed. A few, discontinuous, randomly-oriented microcracks are observed in the body of the topping; these microcracks are not related to any deleterious reactions within the concrete. Secondary ettringite deposits line some voids. Trace amount of clear to milky white alkali-silica reaction (ASR) gel deposits is observed in a void; no distress (cracks or microcracks) is associated with the gel deposits.

Bonding between the concrete topping and the base concrete is weak. The yellowish resinous bonding agent is locally separated from the underlying base concrete. The bonding agent is locally somewhat soft (likely indication of deterioration).

BASE CONCRETE

Aggregate

Coarse: Gravel consisting mainly of limestone and dolomitic limestone with lesser chert and other siliceous rocks.

Fine: Siliceous and calcareous sand consisting of quartz, feldspar, limestone, quartzite, igneous rocks, sandstone, chert, and relatively small amounts of other rocks/minerals.

Gradation & Top Size: Visually appears evenly graded to an observed top size of 0.8 in. (18 mm).

Shape, Texture, Distribution: Coarse – mostly rounded to subangular and equant to oblong with generally smooth surface texture; uniformly distributed. Fine – mostly sub-angular to rounded and equant to oblong; uniformly distributed.

Paste

Color: Light to light medium gray.

Hardness: Moderately hard; locally moderately soft along cracks.

Luster: Dull to subvitreous; dull along cracks.

Paste-Aggregate Bond: Paste-aggregate bond is not evaluated due to abundance of cracks.


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Air Content: Less than 1%; the concrete is not air entrained.

Depth of Carbonation: Localized paste carbonation is observed along the top surface of the base concrete, and along some cracks.

Calcium Hydroxide*: Calcium hydroxide is not observed; possible leached.

Residual Portland Cement Clinker Particles*: Relics and small amounts of partially hydrated, coarse (up to 0.008 in. or 200 μm) portland cement particles are randomly distributed in the paste.

Supplementary Cementitious Materials*: None observed.

Secondary Deposits: Many cracks and microcracks are lined with ettringite, calcium carbonate, and small amount of wedge-shaped crystals (likely gypsum). Small amounts of clear to milky white, alkali-silica reaction (ASR) gel deposits locally line a few cracks and voids.

Cracking: Closely-spaced, sub-horizontal cracks are observed throughout the depth, passing through and around aggregate particles.

Microcracking: Sub-horizontal microcracks are abundant through the depth of the concrete, passing through and around aggregate particles.

Estimated Water-Cement Ratio: Not estimated due severity of distress (cracks and microcracks).

Miscellaneous: The hardened paste is fairly dense in the intact areas away from the cracks. The paste is locally absorptive along the cracks.

_____________________ *percent by volume of paste

inspection and evaluation of concrete in 1913 facilities

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