preliminary stadium concourse distress evaluation

Preliminary Stadium Concourse

Distress Evaluation

PROJECT FILE NO.

12994

STRUCTURE IDENTIFICATION

Allen Independent School District

Allen Eagle Stadium

Allen, Texas

PREPARED FOR

Mark A. Walsh

Saunders, Walsh & Beard

6850 TPC Drive, Suite 210

McKinney, Texas 75070

January 15,2014

Mark A. WalshSaunders, Walsh & Beard6850 TPC Drive, Suite 210McKinney, Texas 75070

File: Allen lndependent School DistrictAllen Eagle StadiumAllen, Texas

Nelson File No.: 12994

Dear Mr. Walsh:

Nelson Architectural Engineers, lnc. dba Nelson Forensics is pleased to submit thispreliminary repoft for the above-referenced file. By signature below, this report wasauthored by and prepared by the undersigned professional.

Please contact us if you have any questions regarding this report.

With kindest regards,

NELSON FORENSICSTexas Certificate of Registration # F-950N ationwide Experts and Consultants

Ryan T. Chancey, Ph.D., P.E.Executive Director of Operations

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Preliminary Stadium Concourse Distress Evaluation Project Name: Allen Eagle Stadium

January 15, 2014 Nelson File No.: 12994

Page 1

AUTHORIZATION AND PURPOSE

Nelson Architectural Engineers, Inc. dba Nelson Forensics (Nelson) was authorized by

Mr. Mark Walsh with Saunders, Walsh & Beard (client) to investigate the distress to the

concrete materials at the concourse level of the Allen Eagle Stadium in Allen, Texas.

Nelson was tasked with determination of the potential cause(s) of the distress, the effect(s)

of the distress on the strength and serviceability of the structure, and provision of

conceptual alternatives for repair/remediation of the distressed concrete.

This report is preliminary in nature, and the findings herein are based upon a preliminary

investigation, limited document review, and limited testing program. Nelson reserves the

right to supplement or change the preliminary opinions presented herein upon further

investigation, document review, testing, and analysis.

This report was not prepared for use in a real estate transaction. It was prepared for the

purpose and for the client as indicated above. Any and all usage or reliance upon this

report by parties other than the client is expressly prohibited.

SCOPE OF INVESTIGATION

Nelson performed a preliminary review of received information pertaining to the subject

structure, including construction drawings, specifications, concrete mix designs, concrete

field reports, and concrete test reports. Nelson observed the exposed portions of the top

surface of the concourse level concrete and observed the bottom surface where accessible

from below. Nelson developed a distress map indicating locations, lengths, and widths of

cracks in the concrete; and photographically documented observed distress and general

conditions.

Nelson coordinated and observed the extraction of three cylindrical concrete core

samples from the concourse level of the stadium. Nelson coordinated evaluation of the

extracted samples in accordance with ASTM C856: Standard Practice for Petrographic

Examination of Hardened Concrete. The evaluation was performed by DRP Consulting,

Inc. as a subcontractor to Nelson.

I N T R O D U C T I O N



Page 2

DESCRIPTION OF STRUCTURE

The subject structure is a multi-purpose stadium with a seating capacity of approximately

18,000. The stadium was reportedly constructed from mid-2010 until the summer of

2012. Construction drawings, specifications, concrete mix designs, concrete field reports,

and concrete test reports were provided for Nelson's review at the time of this writing.

The stadium features four distinct "levels," as indicated on the architectural drawings:

The event level, the concourse level, the upper deck level, and the press box level.

The athletic field is situated outdoors on the event level; and athletic offices, locker

rooms, practice rooms, a weight room, and other facilities are located at the event level

perimeter, in enclosed areas beneath the concourse level.

The concourse level is the subject of Nelson's current investigation, and is the main

assembly level of the stadium. Event attendees enter and exit the facility and access event

seating on the concourse level. The concession and other attendee assembly areas are

located on the concourse level. The concourse level is constructed of conventionally

reinforced concrete slabs-on-grade and an elevated, conventionally reinforced, cast-in-

place one-way concrete joist floor system, commonly known as "pan-joists." The

elevated joist floor system sections span over the enclosed, event-level facilities

mentioned above.

The combined area of the exposed slabs on grade is approximately 22,000 s.f. (square

feet). The combined area of the exposed portions of the elevated joist floor system is

approximately 66,000 s.f. Additional areas of the concourse level are located within

concession areas and other enclosures, and were not subject to the preliminary phase of

Nelson's investigation.



Page 3

For discussion purposes, the front of the structure was assumed to face west.

Photographic documentation and other field-obtained data are being maintained in

Nelson's file. Select photographs are included within the body of this section. A

schematic drawing indicating the general configuration of the concourse level of the

structure, areas of distress, test areas, and other data collected is retained in Nelson's

project file.

Nelson observed pervasive cracking at the concrete comprising the concourse level of the

stadium. The cracks varied from hairline in width to over 0.30" in width. The fracture

surfaces appeared sharp and lustrous, with some notable abrasion near the top (wearing)

surface.

The cracks in the concrete slabs on grade typically propagated perpendicular to saw cut

contraction joints. Diagonal cracks were observed in irregularly-shaped panels, and some

radial fractures were observed near panel corners.

The majority of the cracks within the elevated joist floor system propagated parallel to the

span of the joists. Other cracks propagated approximately perpendicular. The cracking

was pervasive in all areas of the elevated joist floor system, and particularly severe near

the northwest portion of the concourse level.

Photographs representative of the concrete cracking distress are presented on the

following pages.

O B S E R V A T I O N S



Page 4

Figure 1: Concrete cracks at elevated joist floor system

Figure 2: Concrete crack at elevated joist floor system; northwest concourse



Page 5

Figure 3: Close-up of cracks shown in Figure 2; red dot indicates core sample location

Figure 4: View of bottom side of elevated floor joist system showing moisture

penetration through cracks in concrete



Page 6

Nelson coordinated petrographic examination of three extracted concrete core samples

with DRP Consulting, Inc. (DRP). DRP was tasked with investigating the condition and

composition of the concrete represented by the cores. Testing performed by DRP

involved petrographic analysis of the three cores in accordance with ASTM C856:

Standard Practice for Petrographic Examination of Hardened Concrete.

DRP issued a report of findings titled, Petrographic Investigation of Concrete Cores from

Pan Slabs at the Eagle Stadium Located in Allen, Texas, dated January 2, 2014. DRP's

report has been included as an appendix to this preliminary report.

T E S T I N G P E R F O R M E D



Page 7

Concrete is an inherently heterogeneous material composed of coarse aggregate (rock),

fine aggregate (sand), cement, water, and various chemical and mineral admixtures. The

water, cement, and admixtures form a paste that serves as "glue" to bind the aggregates

together. Immediately after mixing, the concrete is in a plastic, or fluid, state. The

cement then reacts with the water through a series of chemical hydration reactions,

causing solid reaction products to form, making the concrete "set," or harden. For the

purposes of this report, the water, cement, and admixture blend will be referred to as the

"paste" in the mix and the aggregates will be referred to as such.

Concrete cracking is caused by restraint of volume change, commonly brought about by a

combination of factors, including drying shrinkage, thermal contraction, curling,

settlement of the soil-support system, and superimposed loads.

After hardening, concrete begins to shrink as water not consumed by cement hydration

leaves the system. As the concrete shrinks, tensile stresses develop in the concrete that

are resisted by restraint provided by other structural members, such as beams and

columns, or by the concrete substrate.

Since all concrete has some shrinkage potential, steel reinforcement is typically provided

within the concrete section to combat volumetric contraction due to drying shrinkage.

When the shrinkage reinforcement provided is inadequate or when the shrinkage of the

concrete is excessive, the internal tensile stresses in the shrinking member exceed the

tensile capacity of the material and fractures develop in the concrete. In addition to

shrinkage steel, joints are typically provided in on-grade concrete flatwork, which control

the location of cracks. The American Concrete Institute (ACI) has established industry

standard provisions for design of shrinkage reinforcement and for jointing of on-grade

concrete.

The amount of concrete drying shrinkage can be reduced by taking practical measures

when placing the concrete, including placing concrete with the lowest possible water

content capable of achieving the desired mix design, and proper curing. The primary

purpose of curing is to slow the loss of moisture from the slab. Moisture retention, or

curing, can be enhanced by several methods including moisture addition, moisture-

retaining covers, and liquid membrane-forming curing compound. The failure to

promptly cure concrete and/or improper curing can lead to cracking of the concrete.

Nelson observed widespread, pervasive fracturing of the concrete slabs on grade and

elevated joist floor system. Fractures were generally oriented either parallel or

perpendicular to one another. Many of the fractures extended through the full depth of

the elevated floor joist system concrete, as evidenced by observations made from below

D I S C U S S I O N A N D A N A L Y S I S



Page 8

the elevated slabs. The uniform and systematic presentation of the distress is consistent

with the accumulation of tensile forces fracturing the slab at regular intervals and being

exacerbated by restraint provided at resisting elements. In Nelson's experience, such

fractures are caused by drying shrinkage of concrete. Tensile stresses developed in the

material due to concrete shrinkage have exceeded the tensile capacity of the material,

causing the observed fractures.

DRP stated that the constituents and proportioning in each of the extracted concrete core

samples is similar, the cement is normally hydrated, and that the physical and optical

properties of the paste were consistent with the provided mix design. DRP reported a

cold joint near the top surface in one of the three samples, accompanied by water voids,

adhesion cracks, and microcracks. All three samples exhibited darker paste and

carbonation near the top surface. These features decrease the durability of wearing

surfaces and increase the potential for drying shrinkage of the concrete, corroborating

Nelson's causal analysis of the manifestations and patterns of observed distress. The

features revealed through petrographic examination are indicative of poor placement,

finishing, and/or curing of the concrete.

Based on observations, testing performed, engineering analysis, and experience, it is

Nelson's preliminary opinion that the observed cracking is the result of drying shrinkage

of the concrete. Further, it is Nelson's opinion that the cracking experienced by the

subject structure is well in excess of cracking that is normal and acceptable in a

concrete structure of this type. Further investigation is necessary to determine the

cause(s) of the excessive drying shrinkage. Potential causes identified as a result of

Nelson's preliminary investigation include improper concrete placement, improper

concrete finishing, improper concrete curing, and improper structural design of

reinforcing steel to control shrinkage cracking.

The observed cracking decreases the durability of the concrete through increased

susceptibility to moisture intrusion and subsequent freeze-thaw attack, chloride attack,

mild chemical exposure, and accelerated corrosion of reinforcing steel. The cracking has

decreased the service life of the structure and potentially decreased its structural capacity.

Prompt remediation is necessary to mitigate further distress to the concrete materials and

the structural load resisting system.

Full depth fracturing of the concrete joist floor system has resulted in a condition where

the compression stress block of the slab may no longer engage immediately when the

system is loaded. When the system is loaded, the slab must deflect and the separation

close at the fracture before the slab can transfer mid-span compressive forces at the top

fiber between the two sides of the fracture. Additionally, excessive crack widths may

affect the shear capacity of the concrete due to the loss of aggregate interlock across the

fracture planes. Further investigation is necessary to quantify the effect of the cracking on

the structural capacity of the joist floor system.



Page 9

Based on observations, testing performed, engineering analysis, and experience, Nelson is

of the following preliminary opinions regarding the distress to the concourse level

concrete at the Allen Eagle Stadium:

The observed cracking is the result of drying shrinkage of the concrete.

The cracking experienced by the subject structure is well in excess of cracking that

is normal and acceptable in a concrete structure of this type.

Further investigation is necessary to determine the cause(s) of the excessive drying

shrinkage. Potential causes identified as a result of Nelson's preliminary

investigation include improper concrete placement, improper concrete finishing,

improper concrete curing, and improper structural design of reinforcing steel to

control shrinkage cracking.

The observed cracking decreases the durability of the concrete through increased

susceptibility to moisture intrusion and subsequent freeze-thaw attack, chloride

attack, mild chemical exposure, and accelerated corrosion of reinforcing steel.

The cracking has decreased the service life of the structure.

The cracking has potentially decreased the structural capacity of the elevated joist

floor system. Further investigation is necessary to quantify the effect of the

cracking on the structural capacity of the joist floor system.

Prompt remediation is necessary to mitigate further distress to the concrete and the

structural load resisting system.

P R E L I M I N A R Y C O N C L U S I O N S



Page 10

As previously stated, the cracking observed at the concourse level of Allen Eagle Stadium

decreases the durability of the concrete. The cracking has decreased the service life of

the structure and potentially decreased its structural capacity. Prompt remediation is

necessary to mitigate further distress to the concrete materials and the structural load

resisting system.

Based on Nelson's preliminary evaluation and consultation with repair material

manufacturers, Nelson is of the opinion that the distressed concrete slabs on grade should

be removed and replaced.

Based on Nelson's preliminary evaluation and consultation with repair material

manufacturers, Nelson presents four alternatives for remediation to address and mitigate

the observed distress to the elevated joist floor system. Nelson's investigation is ongoing

and further remedial measures may be necessary to address material and/or structural

deficiencies. The four conceptual alternatives are as follows:

1. Remove and replace the elevated joist floor systems with a properly designed

and constructed system. This option will involve demolition of major structural

and non-structural components, possibly including finished event-level facilities.

The advantage of this option is that the repaired structure will be most similar in

aesthetics and performance to the as-designed original structure, and the service

life will not be diminished from the original design intent.

Disadvantages of this option include substantial interruption to the usability of the

facility during the timeframe of the repairs, which is on the order of magnitude of

months. Further, this will likely be the most costly option from an initial capital

expenditure perspective.

2. Rout and seal cracks less than 0.02" in width; epoxy inject cracks of 0.02" and

greater in width. Epoxy injection is a rigid structural repair intended to restore the

structural capacity of the concrete, as properly injected cracks are stronger than the

surrounding concrete. Epoxy injection also seals the cracks, preventing intrusion

of water and other chemicals. Routing and sealing is a nonstructural repair that

consists of enlarging the top surface of smaller cracks by mechanical means

(routing) and filling the enlarged crack with a suitable joint sealant.

C O N C E P T U A L R E M E D I A T I O N S O L U T I O N S



Page 11

Advantages of this option include a relatively expedient repair process that can be

conducted in phases, allowing the facility as a whole to operate while pre-

determined sections are systematically repaired. Further, this option is likely the

most inexpensive from an initial capital expenditure perspective.

Disadvantages of this option include diminished aesthetics, as the repaired cracks

will be visually accented due to the contrast of the repair material with the

substrate concrete, giving a "spider web" appearance. Also, the sealer used in the

routed cracks will require periodic repair, maintenance, and re-application.

3. Epoxy inject cracks of 0.02" and wider. Apply a low-viscosity, gravity-fed repair

material to the top surface of the entire elevated slab. The repair material is

applied to the entire concrete surface as a flood coat, and subsequently permeates

into cracks under the force of gravity and hardens, bridging the cracks.

Advantages of this option include a wearing surface with similar aesthetics as the

current, cracked concrete; and a relatively expedient repair process that can be

conducted in phases, allowing the facility as a whole to operate while pre-

determined sections are systematically repaired.

Disadvantages of this option include potentially poor penetration of the repair

material into larger cracks and cracks contaminated with moisture or detritus. This

causes concern with the subject project considering the pervasive nature of the

cracking and the exposure conditions. Further, sand is typically broadcast on the

wearing surface following application of the repair material to scarify the surface

and provide slip-resistance. The sand is sacrificial, and will become detached

from the wearing surface with use, typically over the course of months, resulting in

a substantial and recurring volume of sand granules atop the wearing surface and

underfoot. The existing concrete cracks will be visible.

This option is likely to be more costly than Option 2 from an initial capital

expenditure perspective, and will require periodic maintenance.

4. Rout and seal cracks less than 0.02" in width; epoxy inject cracks of 0.02" and

greater in width, then install a liquid-applied, heavy duty pedestrian traffic

membrane. This hybrid solution restores the structural capacity of the structure,

seals structural and non-structural cracks, and provides a durable, non-slip, and

aesthetically pleasing wearing surface which prevents water and chemical

intrusion into the concrete.



Page 12

As an alternative to epoxy injection, external reinforcement with fiber-reinforced

polymer applied to the bottom surface of the elevated floor joist system may be

considered.

Advantages to this solution include a redundant system which includes both

sealing of individual cracks and the application of a durable membrane overlay.

The elastic overly provides a slip-resistant traffic surface, and will bridge cracks

which develop following the repair, preventing further distress due to moisture

intrusion. The overlay will be most aesthetically similar to the finished concrete

surface intended by the original design, short of full replacement of the elevated

floor joist system. This option can be implemented in stages, similar to Options 2

and 3.

Disadvantages of this option include the initial capital expenditure, which is

greater than that of Options 2 and 3, but less than full removal and replacement.

Further, this option will require periodic inspection and re-application of at least

one coat of the membrane.

Recommended repairs are provided as a basis for an opinion of probable construction

cost of repair (cost estimate). Each repair item will require unique design/construction

expertise and require construction documents prepared by a design professional. Project-

specific cost estimating is required to develop cost estimates for the implementation of

each option, and further analysis is required to determine the life-cycle cost of each

option.



Page 13

Further investigation is necessary to determine the effect of the observed cracking on the

capacity of the joist floor system and the cause(s) of the excessive drying shrinkage.

Nelson recommends the following scopes of further investigation:

Structural Capacity Analysis: Nelson recommends a targeted structural analysis of the in-

situ elevated joist floor system, considering the influence of the observed and measured

cracking. Nelson estimates fees for this analysis of $15,000.

Concrete Materials Evaluation, Testing, and Analysis: To date, Nelson has conducted a

preliminary investigation only. Nelson recommends proceeding with the balance of the

scope of work presented in its June 4, 2013 proposal entitled Forensic Engineering,

Concrete Distress, and Water Intrusion Consulting Relating to Allen Eagle Stadium. The

June 4, 2013 proposal is attached as an appendix to this preliminary report.

The balance of the scope of work proposed includes a detailed review of design and

construction documentation; further on-site evaluation, data collection, and

documentation; a rigorous petrographic analysis of additional concrete material samples;

parametric analysis of design specifications, construction records, and testing results to

identify specific design and/or construction deficiencies which caused the shrinkage

cracking; and preparation of a written reports of findings.

Nelson estimates fees for the balance of the proposed scope of work of $100,000.

R E C O M M E N D A T I O N S



Page 14

The items observed and documented in this report are intended to be representative of

the condition of the concrete materials at the concourse level of the subject structure. No

attempt has been made to document the condition of each and every structural or

nonstructural element. Only visible items were observed and documented.

This document is the rendering of a professional service, the essence of which is the

provision of advice, judgment, opinion, or professional skill.

This report was prepared in order to document distress observed in the concrete of the

concourse level of the subject structure. The opinions presented herein are based on site

observations, field information and measurements taken, written and verbal information,

testing, and experience, where applicable. No complete review of this structure's

conformance to current or previously applicable building codes was performed.

However, specific items that may be at issue with the applicable building code

requirements may be noted.

This report should not be construed as an assessment of total damages to the structure at

the time of site observation. In addition to the observed and documented items of

distress, hidden defects may exist that were not readily visible. Also, some damaged

areas may have been previously repaired and, unless otherwise noted, were not visible at

the time of observation. However, these areas may experience future distress. No

representation, guarantee, or warranty as to the future performance of this structure is

made, intended, or implied.

Additional construction documents prepared by a design professional may be required

and are beyond the scope of this assignment.

In the event that additional information becomes available that could affect the

conclusions reached in this investigation, this office reserves the right to review, and, if

required, change some or all of the opinions presented herein.

This report has been prepared for exclusive use of the client and its representatives. No

unauthorized re-use or reproduction of this report, in part or whole, shall be permitted

without prior written consent.

Alteration of this document in any way by anyone other than the professional (or

professionals) whose seal (or seals) appear on the documents, in either hard copy or

electronic form, is strictly prohibited and may constitute a violation of state and/or federal

laws.

L I M I T A T I O N S

AP

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IX

APPENDIX

Petrographic Investigation of Concrete Cores from Pan Slabs at the Eagle Stadium Located in

Allen, Texas

Prepared for: Mr. Ryan Chancey, Ph.D., P.E. Nelson Architectural Engineers, Inc. Plano, Texas

Prepared by: David Rothstein, Ph.D., P.G., FACIReport No.: DRP13.1148

2 JANUARY 2014

DRP Consulting, Inc. 3200 Carbon Place #104 Boulder, CO 80301www.drpcinc.com

EXECUTIVE SUMMARY

Three (3) cores extracted from a concrete pan slab at the Eagle Stadium located in Allen, Texas are subjects of petrographic examination to determine the general condition of the concrete and potential causes of random cracking. Core C-1 is from an area with random cracking and contains a through-going crack whereas Core C-2 and Core C-3 do not include macroscopic cracks. The findings described above indicate that the constituents and proportioning of the three cores is similar. The cores consist of hydrated portland cement with fly ash, coarse aggregate that consists of crushed limestone with a 19 mm ( in.) nominal top size and fine aggregate that consists of a natural siliceous sand. All three cores lack air entrainment with less than 3% total air (by visual estimation).

Core C-1 shows a through-going sub-vertical crack that cuts around aggregate particles over the full depth of the core and is free of secondary deposits. Such cracks are typical of early-age drying shrinkage. Core C-1 also shows a small cold joint near the top of the core. This cold joint is defined by a sharp line of carbonated paste that cuts obliquely from 3-9.5 mm (- in.) below the finished surface. The cold joint does not necessarily represent different loads of concrete but a discontinuity in placement and finishing. Above the cold joint water voids and adhesion cracks and microcracks are more abundant than below the feature. Core C-1 shows a very thin (~ 100 m or 4 mil) layer of white paste at the top of the core, suggesting water was worked into the slab.

Core C-2 is well consolidated and shows minimal microcracking near the top surface. Core C-3 shows some water voids and adhesion microcracks in the top 9.5-19 mm (- in.) of the core. Neither of these two cores show macroscopic cracking due to drying shrinkage or any other mechanism.

All three cores show a layer of darker paste that extends for 1-3 mm (40-120 mil) below the top surface. Such zones are typical of concrete that is poorly cured. All three cores also show that this layer does not stain purple by phenolphthalein, indicating the paste is carbonated. This layer is relatively deep given the age and quality of the concrete, which is also typical of poor curing. Poor curing tends to diminish the durability of wear surfaces and can increase the potential for shrinkage cracking.

Other factors not observable with a microscope may contribute to the potential for shrinkage cracking. These include external factors such as design, detailing, construction practices, thermal stresses, and loading both during and after construction.

Materials properties can also affect the potential for shrinkage cracking. Some of these properties, which are quite difficult to track via petrography of hardened concrete, include the chemical composition and fineness of cement and cement-admixture interactions. Note that while some high-range water reducers (HRWR) can increase drying shrinkage, polycarboxylate-

Allen Eagle Stadium Pan Slab Core Petrography! Report No. DRP13.1148Summary Report! 2 January 2014

drpcinc.com ! i

based HRWR (such as the BASF PS 1466 indicated by the mix design) tend to nullify this behavior and is typically offset by the reduction in water content afforded by use of the admixture.

Other materials properties that influence shrinkage are readily tracked via petrography. The size and gradation of aggregates along with the paste and water content of a concrete mixture tend to have the most significant affects on the potential for shrinkage. Quantitative determinations of the proportions of paste and aggregate are possible to obtain via ASTM C457; DRP recommends completion of such tests to obtain this information. This testing, along with petrographic examinations of cores from other locations in the project may provide more insight toward the factors contributing to the cracking of the structure.


drpcinc.com ! ii

1.0 INTRODUCTION

Mr. Ryan Chancey, Ph.D., P.E. of Nelson Architectural Engineers, Inc. (NAI) located in Plano, Texas requested DRP Consulting, Inc. (DRP) to investigate the condition of concrete represented by cores extracted from pan slabs at the Eagle Stadium located in Allen, Texas. On 26 November 2013 DRP received three (3) concrete cores from NAI. The cores were designated by NAI as Core C-1 to Core C-3 and were assigned DRP sample numbers 17YD6545-17YD6547, respectively. Core C-1 represented an area where cracking of the pan slab was observed, the other two cores were not cracked.

Mr. Chancey provided concrete mix design submittal information, photographs of the coring locations, concrete field reports and preliminary crack maps. The concrete for the project was supplied by Redi-Mix Concrete, L.P. in Euless, Texas. The mix number was 10N11623. Table 1 summarizes information relevant to the mix design.

Table 1. Redi-Mix Concrete Mix No. 10N11623Component Quantity (per cubic yard)

Cemex Balcones ASTM C150 Type I-II Portland Cement 527 (lbs)Lafarge Walsh ASTM C618 Type C Fly Ash 131 (lbs)Martin Marietta Chico Quarry ASTM C33 #67 Coarse Aggregate 1830 (lbs)Redi-Mix Concrete ASTM C33 Concrete Sand 1340 (lbs)Water 29 (gallons)BASF PS 1466 ASTM C494 High Range Water Reducing Admixture 8-10 oz/cwt

Physical PropertiesPhysical PropertiesSlump, inches 8 +/1 1 in.Water-Cementitious Materials Ratio 0.37Concrete Strength @ 28 days, psi 4500Concrete Strength @ 3 days, psi 3500Air Content 1.5 1.5%Unit Weight, pcf 150.7

2.0 SCOPE OF WORK

The testing on all three cores involved petrographic analysis according to ASTM C856 [1]. The examinations included thin section analysis for Core C-1; the other two examinations were done without thin sections. This report summarizes the major findings from the investigation. Appendices A-C contain the notes, photographs and micrographs from the petrographic examinations. Appendix D describes the procedures used to complete this scope of work.


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1 Standard Practice for Petrographic Examination of Hardened Concrete. Annual Book of ASTM Standards, Vol. 4.02., ASTM C856-13.

3.0 FINDINGS

The following findings are relevant to the concrete represented by the cores.

3.1 Core Dimensions, Orientation and As-Received Condition The cores are vertical in orientation and measure 90 mm (3 in.) in diameter and 125-130 mm (5-5 in.) in length (Figure 1). The cores span from the finished surface to the cast surface and represent the full thickness of the pan slab. Each core has a broom finish and was cast on a smooth substrate. The cores are hard and compact. No steel reinforcement or other embedded items were observed in the cores.

(a) (b)

(c)

Figure 1. Photographs showing (a) Core C-1, (b) Core C-2 and (c) Core C-3 in their as-received condition. The yellow scale is ~ 150 mm (6 in.) long.



3.2 Components: Cementitious Materials The physical properties of the paste, such as color, luster, texture and hardness, are similar in all three cores (Figure 2). The paste consists of hydrated portland cement and fly ash; no slag cement or other supplemental cementitious materials were observed (Figure 3). The paste is gray in color with a smooth texture and sub-vitreous luster. The hydration of the cement is normal and the physical and optical properties of the paste are consistent with the mix design. Calcium hydroxide is fine-grained and evenly distributed. A layer of darker paste was observed for ~ 2 mm (80 mil) at the top of each core (Figure 4). In Core C-1 a layer of white paste that is ~ 100 m (4 mil) thick is present on the top of the core.

(a) (b) (c)

Figure 2. Reflected light photomicrographs of polished surface of (a) Core C-1, (b) Core C-2, and (c) Core C-3 showing typical texture, color and luster of the paste. The red arrows in each figure indicate grains of fly ash.

(a) (b)

Figure 3. Transmitted light photomicrographs of thin section from Core C-1 showing paste in (a) plane-polarized and (b) cross-polarized light. The red and blue arrows in (a) indicate relict and residual cement grains and fly ash, respectively.



(a) (b)

Figure 4. Photographs of the polished surface of (a) Core C-1 and (b) Core C-2 showing variations in paste color at the top of the cores. The scale is in millimeters in both photos.

3.3 Components: Air Voids The cores are not air-entrained and contain less than 3% total air by visual estimation (not determined by ASTM C457). In Core C-1 numerous water voids, adhesion cracks and microcracks and other irregular voids were observed for up to 9.5 mm ( in.) from the top surface (Figure 5). Core C-2 is well consolidated with no significant water voids observed. Core C-3 shows water voids within ~ 15 mm ( in.) of the top surface (Figure 5).

(a) (b)

Figure 5. Reflected light photomicrographs of polished surface of (a) Core C-1 and (b) Core C-3 showing irregular voids (red arrows) near the top of the core.



3.4 Components: Aggregates The cores contain similar aggregates (Figure 6). The coarse aggregate is a crushed limestone with a 19 mm ( in.) nominal top size. The rocks are hard and competent. Most of the limestones are bioclastic with abundant fossils, ooids and occasional pellets. Traces of silicification were observed rarely. The fine aggregate is a natural sand that is siliceous in composition except for occasional particles of limestones that appear derived from crushing of the coarse aggregate. The sand consists of quartz, quartzite, feldspar and chert. Many of the components of the fine aggregate are potentially susceptible to alkali-silica reaction (ASR). No evidence of ASR or other adverse aggregate reactions was observed in any core.

(a) (b)

(c) (d)

Figure 6. (a) Photograph of polished surface of Core C-2 showing coarse aggregate; scale in millimeters. (b) Reflected light photomicrograph of polished surface of Core C-2 showing sand. (c) Photograph of polished surface of Core C-3 showing coarse aggregate; scale in millimeters. (d) Reflected light photomicrograph of polished surface of Core C-3 showing sand.



3.5 Cracking & Microcracking Core C-1 showed the most significant cracking and microcracking (Figure 7). In this core a crack cut sub-vertically through the full thickness of the core. The crack cuts around aggregate particles and is free of secondary deposits. Because the crack cut the core in two pieces it was not possible to measure the width of the crack. A smaller crack occurred as a splay off of the main crack and also cut through the full depth of Core C-1. This crack measured up to 125 m (5 mil) in width. Microcracks were observed that struck sub-parallel to the larger crack in Core C-1 as well. Adhesion cracks and microcracks were observed in abundance, along with water voids, for up to 9.5 mm ( in.) from the top surface of Core C-1 (Figure 8). These are most abundant along an oblique feature interpreted to represent a cold joint (Figure 8). Core C-2 and C-3 show minor microcracking at the top surface typical of shrinkage.

(a) (b)

Figure 7. (a) Photograph of the side of Core C-1 showing through-going crack (red arrows) that split the core in two. (b) Reflected light photomicrograph showing microcrack (red arrows) that is sub-parallel to the main crack (green arrows).

(a) (b)

Figure 8. (a) Reflected light photomicrograph of the polished surface of Core C-1 showing cold joint (red arrows). The green arrows indicate irregular voids and adhesion microcracks, which are more abundant above the joint. (b) Cross-polarized transmitted light photomicrograph of thin section showing cold joint (red arrows). Note carbonation of the paste along the joint.



3.6 Secondary Deposits All three cores show a veneer of carbonated paste at the top of the core, based on phenolphthalein staining (Figure 9) and phenolphthalein staining and thin section microscopy for Core C-1. In Core C-1 carbonation reaches a depth of ~ 1 mm (40 mil) except near the main crack, where carbonation occurs to a depth of ~ 6 mm ( in.). Core C-1 does not show significant carbonation along the walls of the main crack below 6 mm ( in.). In Core C-2 and Core C-3 carbonation ranges from 1-3 mm (40-120 mil) deep. Trace deposits of ettringite were observed in air voids in all three cores. No other secondary deposits were observed.

(a) (b)

(c) (d)

Figure 9. Photographs of phenolphthalein stained surfaces. (a) Overview of stained surface of Core C-1 and (b) detail of the surface at the top of Core C-1. (c) Detail of surface near the top of Core C-2. (d) Detail of surface near the top of Core C-3. Scale in millimeters in (b), (c) and (d).



4.0 CONCLUSIONS

The findings described above indicate that the constituents and proportioning of the three cores is similar. The cores consist of hydrated portland cement with fly ash, coarse aggregate that consists of crushed limestone with a 19 mm ( in.) nominal top size and fine aggregate that consists of a natural siliceous sand. All three cores lack air entrainment with less than 3% total air (by visual estimation).

Core C-1 shows a through-going sub-vertical crack that cuts around aggregate particles over the full depth of the core and is free of secondary deposits. Such cracks are typical of early-age drying shrinkage. Core C-1 also shows a small cold joint near the top of the core. This cold joint is defined by a sharp line of carbonated paste that cuts obliquely from 3-9.5 mm (- in.) below the finished surface. The cold joint does not necessarily represent different loads of concrete but a discontinuity in placement and finishing. Above the cold joint water voids and adhesion cracks and microcracks are more abundant than below the feature. Core C-1 shows a very thin (~ 100 m or 4 mil) layer of white paste at the top of the core, suggesting water was worked into the slab.

Core C-2 is well consolidated and shows minimal microcracking near the top surface. Core C-3 shows some water voids and adhesion microcracks in the top 9.5-19 mm (- in.) of the core. Neither of these two cores show macroscopic cracking due to drying shrinkage or any other mechanism.

All three cores show a layer of darker paste that extends for 1-3 mm (40-120 mil) below the top surface. Such zones are typical of concrete that is poorly cured. All three cores also show that this layer does not stain purple by phenolphthalein, indicating the paste is carbonated. This layer is relatively deep given the age and quality of the concrete, which is also typical of poor curing. Poor curing tends to diminish the durability of wear surfaces and can increase the potential for shrinkage cracking.

Other factors not observable with a microscope may contribute to the potential for shrinkage cracking. These include external factors such as design, detailing, construction practices, thermal stresses, and loading both during and after construction.

Materials properties can also affect the potential for shrinkage cracking. Some of these properties, which are quite difficult to track via petrography of hardened concrete, include the chemical composition and fineness of cement and cement-admixture interactions. Note that while some high-range water reducers (HRWR) can increase drying shrinkage, polycarboxylate-based HRWR (such as the BASF PS 1466 indicated by the mix design) tend to nullify this behavior and is typically offset by the reduction in water content afforded by use of the admixture.



Other materials properties that influence shrinkage are readily tracked via petrography. The size and gradation of aggregates along with the paste and water content of a concrete mixture tend to have the most significant affects on the potential for shrinkage. Quantitative determinations of the proportions of paste and aggregate are possible to obtain via ASTM C457 [2]; DRP recommends completion of such tests to obtain this information. This testing, along with petrographic examinations of cores from other locations in the project may provide more insight toward the factors contributing to the cracking of the structure.

This concludes work performed on this project to date

David Rothstein, Ph.D., P.G. FACI



2 Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete, Annual Book of ASTM Standards, Vol. 4.02, ASTM C457-12.

Allen Eagle Stadium Pan Slab Core Petrography

Appendices

Appendix A! ! Core C-1 Petrography (ASTM C856)Appendix B! ! Core C-2 Petrography (ASTM C856)Appendix C !! Core C-3 Petrography (ASTM C856)Appendix D! ! Procedures

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1. RECEIVED CONDITION1. RECEIVED CONDITION

ORIENTATION Vertical core taken through elevated slab measures 90 mm (3 in.) in diameter and 125 mm (~ 5 in.) in length (Figure A1, A2).

SURFACES Top surface has a light broom finish and the bottom surface is cast against a smooth substrate such that the core represents the full thickness of the slab (Figure A3). GENERAL

CONDITIONThe concrete is hard and compact and rings lightly when sounded with a hammer.A sub-vertical crack cuts the core in two pieces.

2. EMBEDDED OBJECTS2. EMBEDDED OBJECTSGENERAL None observed.

3. CRACKING3. CRACKING

MACROSCOPIC

Main crack cuts the core into two pieces, such that the original width of the crack could not be measured. The crack cuts around aggregate particles over the full depth of the core (Figure A4). A second crack measuring 100 m (4 mil) wide splays off the main crack on the top surface for a strike length of ~ 25 mm (1 in.; Figure A5). The crack can be traced on the side of the core over the full depth of the core and ranges up to 1.25 mm (50 mil) wide. Adhesion cracks ranging up to 250 m (10 mil) wide and 3 mm ( in.) long are abundant in the top 9.5 mm ( in.) of the slab (Figure A6). Sub-horizontal cracks ranging up to 250 m (10 mil) wide and 6 mm ( in.) long are common in the area of adhesion cracks and microcracks. Some of these cracks merge with consolidation voids. The zone where cracks and water voids are abundant occurs above a distinct linear feature interpreted to represent a cold joint that runs obliquely from 3-9.5 mm (- in.) below the top surface (Figure A7). Below the cold joint adhesion cracks and microcracks and irregular voids are relatively rare. The cold joint is distinguished by lighter paste that was observed in thin section to be pervasively carbonated (Figure A8). No secondary deposits were observed in the cracks.

MICROSCOPIC

Adhesion microcracks are commonly observed in the top 9.5 mm ( in.) of the core. Microcracks that splay off of the main crack described above were observed from about 19-70 mm (-2 in.) below the top surface (Figure A9). These are generally sub-vertical but divert around aggregate particles. The microcracks are up to 100 m (4 mil) wide and segments become hairline cracks that range from 100-250 m (4-10 mil) wide. No secondary deposits were observed in the cracks.

4. VOIDS4. VOIDS

VOID SYSTEMConcrete is not air-entrained and contains less than 3% air by visual estimation (not determined in accordance with ASTM C457) except in the region near the top of the core where water voids and adhesion cracks are abundant (Figure A10).

VOID FILLINGS Voids are mostly free of secondary deposits.

APPENDIX A: Allen Eagle Stadium Core Petrography Report No. DRP13.1148Sample ID: Core C-1 (17YD6545) Date: 27 December 2013

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5. COARSE AGGREGATE5. COARSE AGGREGATEPHYSICAL

PROPERTIES

Crushed limestone with 19 mm ( in.) nominal top size (Figure A11). The rocks are moderately hard and competent. The particles are sub-equant to oblong in shape with sub-angular to sub-round edges. The grading and distribution is relatively even.

ROCK TYPES

The aggregate consists of limestones that are mostly white to light buff in color. Most of the rocks are bioclastic with micritic (very fine-grained) matrices but some bioclastic rocks with sparry layers are also present. The grains consist of fossils, ooids, and occasional pellets. Most of these rocks are matrix-supported but some are grain supported. Some of the darker buff rocks are micritic and show evidence of bioturbation. The limestones do not show evidence of significant silicification.

OTHER FEATURES No deleterious coatings or incrustations observed. No low w/c mortar coatings observed. No reaction rims or evidence of alkali-aggregate reaction (AAR) observed.

6. FINE AGGREGATE6. FINE AGGREGATEPHYSICAL

PROPERTIES

Natural sand consists of rocks that are hard and competent (Figure A12). The particles are sub-equant to oblong in shape with round to sub-angular edges. The grading and distribution are relatively even.

ROCK TYPES

The sand is mostly siliceous in composition but limestone particles that are consistent with the coarse aggregate make up a minor component of the fine aggregate. The sand contains particles of quartz, quartzite, feldspar and chert. Some of these components are potentially susceptible to alkali-silica reaction (ASR).

OTHER FEATURES No deleterious coatings or incrustations observed and no low w/c mortar coatings observed. No evidence of ASR was observed.

7. PASTE OBSERVATIONS7. PASTE OBSERVATIONSPOLISHED SURFACE

Paste is gray (Munsell 2.5Y/6/1), has a smooth texture and sub-vitreous luster, and is hard (Mohs ~ 4; Figure A13) below the cold joint, or over most of the slab. Above the cold joint the paste is gray (2.5Y/5/1) to grayish brown (2.5Y/5/2)

FRESH FRACTURE SURFACE

Fracture surface is dark gray, has a hackly texture and a sub-vitreous luster. The fracture surface cuts mostly around but commonly through aggregate particles (Figure A14). No significant secondary deposits were observed on the surface.

THIN SECTION*

The paste contains hydrated portland cement and fly ash (Figure A15). The hydration is normal. The RRCG consist mostly of belite and interstitial aluminate and ferrite but occasional grains of ferrite were observed as well. No slag cement or other SCM are present. CH makes up 10-15% of the paste, is fine-grained and evenly distributed.

* Abbreviations as follows: RRCG = relict and residual cement grains; SCM = supplemental cementitious materials; CH = calcium hydroxide; ITZ = interfacial transition zone. Modal abundances are based on visual estimations.* Abbreviations as follows: RRCG = relict and residual cement grains; SCM = supplemental cementitious materials; CH = calcium hydroxide; ITZ = interfacial transition zone. Modal abundances are based on visual estimations.

8. SECONDARY DEPOSITS8. SECONDARY DEPOSITS

PHENOLPHTHALEINNo staining for 1 mm (40 mil) from the top surface except near the main crack, where no staining was observed to a depth of ~ 6 mm ( in.; Figure A16).

DEPOSITS No significant deposits were observed. Trace to minor deposits of ettringite were observed in voids.


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FIGURES

(a)

(b)

Figure A1. Photographs showing (a) oblique view of the top and side of the core with identification labels and (b) the top of the core. The red and blue dots in (a) show the orientation of the saw cuts used to prepare the sample.


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(c)

Figure A1 (contd). (c) Photograph showing the bottom of the core.

Figure A2. Photograph showing the polished surface of the core.


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Figure A3. Photograph showing detail of the top surface of the core; scale in millimeters.

Figure A4. Photograph of the side of the core showing main crack (red arrows) cutting around aggregate particles through the full depth of the core.


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Figure A5. Photograph of the top surface showing smaller crack (red arrows) that splays off of the main crack (blue arrows) that cut the core in two; scale in millimeters.

Figure A6. Photograph of the polished surface showing adhesion microcracks and water voids (red arrows) near the top of the core. Scale in millimeters.


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Figure A7. Reflected light photomicrographs of polished surface showing cold joint (red arrows). Note abundance of water voids and adhesion cracks (green arrows) above the cold joint.


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Figure A8. Transmitted light photomicrographs of thin section showing cold joint (red arrows). Note pervasive carbonation of the paste along the joint.


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Figure A9. Reflected light photomicrographs of polished surface showing microcracks (red arrows) near the main crack (green arrows) that cut the core into two pieces.

Figure A10. Reflected light photomicrograph of polished surface showing water voids and consolidation voids (red arrows) near the top of the core.


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Figure A11. Photograph of the polished surface showing coarse aggregate; scale in millimeters.

Figure A12. Reflected light photomicrograph of polished surface showing the fine aggregate.


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Figure A13. (a) Photograph of polished surface showing overview of paste at the top of the core. The scale is in millimeters. (b) Reflected light photomicrograph of polished surface showing detail of paste texture and luster. The red arrows indicate grains of fly ash.


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Figure A14. (a) Photograph and (b) reflected light photomicrograph of fresh fracture surface. The scale in (a) is in millimeters.


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(b)

Figure A15. Transmitted light photomicrographs of thin section from the concrete core showing detail of paste in (a) plane-polarized and (b) cross-polarized light. The red and blue arrows in (a) indicate RRCG and fly ash, respectively.


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Figure A16. Photographs showing (a) overview of phenolphthalein stained surface and (b) detail of surface near the top of the core. Scale in millimeters in (b).


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ORIENTATION Vertical core taken through elevated slab measures 90 mm (3 in.) in diameter and 130 mm (~ 5 in.) in length (Figure B1, B2).

SURFACES Top surface has a light broom finish and the bottom surface is cast against a smooth substrate such that the core represents the full thickness of the slab (Figure B3). GENERAL

CONDITIONThe concrete is hard and compact and rings lightly when sounded with a hammer.


3. CRACKING3. CRACKINGMACROSCOPIC None observed.

MICROSCOPIC

Sub-vertical microcracks that cut to depths of ~ 3 mm ( in.) are abundant at the top of the slab (Figure B4). Most of these microcracks are 25-50 m (1-2 mil). Occasional adhesion microcracks that are less than 50 m (2 mil) wide and 1 mm (40 mil) long were observed in the top 3 mm ( in.) of the core. No secondary deposits were observed in the microcracks, which cut around aggregate particles.

4. VOIDS4. VOIDS

VOID SYSTEMConcrete is not air-entrained and contains less than 3% air by visual estimation (not determined in accordance with ASTM C457). The concrete is well consolidated with no significant bleed voids or consolidation voids observed.


5. COARSE AGGREGATE5. COARSE AGGREGATEPHYSICAL

PROPERTIES

Crushed limestone with 19 mm ( in.) nominal top size (Figure B5). The rocks are moderately hard and competent. The particles are sub-equant to oblong in shape with sub-angular to sub-round edges. The grading and distribution is relatively even .

ROCK TYPES

The aggregate consists of limestones that are white to gray to light buff in color. Most of the rocks are bioclastic and grain supported with fine-grained (micritic) matrices. The rocks mostl commonly contain an abundance of fossils and ooids. Occasional micritic limestones contain pellets and evidence of bioturbation.


APPENDIX B: Allen Eagle Stadium Core Petrography Report No. DRP13.1148Sample ID: Core C-2 (17YD6546) Date: 27 December 2013

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PROPERTIES

Natural sand consists of rocks that are hard and competent (Figure B6). The particles are sub-equant to oblong in shape with round to sub-angular edges. The grading and distribution are relatively even.

ROCK TYPES

The sand is mostly siliceous in composition but limestone particles that are consistent with the coarse aggregate make up a minor component of the fine aggregate. The sand contains particles of quartz, quartzite, feldspar and chert. Some of these components are potentially susceptible to alkali-silica reaction (ASR).

OTHER FEATURES No deleterious coatings or incrustations observed and no low w/c mortar coatings observed. No evidence of ASR was observed.


Paste is gray (Munsell 2.5Y/6/1), has a smooth texture and sub-vitreous luster, and is hard (Mohs ~ 4; Figure B7). The paste is grayish brown (2.5Y/5/2) with a more granular texture and duller luster for up to 2 mm (80 mil) from the top surface.


Fracture surface is gray, has a hackly texture and a sub-vitreous luster. The fracture surface cuts through aggregate particles (Figure B8). No significant secondary deposits were observed on the surface.


PHENOLPHTHALEIN No staining for 1-2 mm (40-80 mil) from the top surface (Figure B9).



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FIGURES

(a)

(b)

Figure B1. Photographs showing (a) oblique view of the top and side of the core with identification labels and (b) the top of the core. The red and blue dots in (a) show the orientation of the saw cuts used to prepare the sample.


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(c)

Figure B1 (contd). (c) Photograph showing the bottom of the core.

Figure B2. Photograph showing the polished surface of the core.


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Figure B3. Photograph showing detail of the top surface of the core; scale in millimeters.

Figure B4. Reflected light photomicrograph of polished surface showing microcracks (red arrows) near the top of the core.


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Figure B5. Photograph of the polished surface showing coarse aggregate; scale in millimeters.

Figure B6. Reflected light photomicrograph of polished surface showing the fine aggregate.


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(b)

Figure B7. (a) Photograph of polished surface showing overview of paste at the top of the core. The scale is in millimeters. (b) Reflected light photomicrograph of polished surface showing detail of paste texture and luster. The red arrows indicate grains of fly ash.


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(b)

Figure B8. (a) Photograph and (b) reflected light photomicrograph of fresh fracture surface. The scale in (a) is in millimeters.


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(b)

Figure B9. Photographs showing (a) overview of phenolphthalein stained surface and (b) detail of surface near the top of the core. Scale in millimeters in (b).


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ORIENTATION Vertical core taken through elevated slab measures 90 mm (3 in.) in diameter and 130 mm (~ 5 in.) in length (Figure C1, C2).

SURFACES Top surface has a light broom finish and the bottom surface is cast against a smooth substrate such that the core represents the full thickness of the slab (Figure C3). GENERAL

CONDITIONThe concrete is hard and compact and rings lightly when sounded with a hammer.


3. CRACKING3. CRACKING

MACROSCOPICSeveral sub-horizontal hairline cracks and adhesion cracks are present from about 9.5-19 mm(- in.) below the top surface (Figure C4). These are 100-250 m (4-10 mil) wide and 2-6 mm (80-240 mil) long, cut around aggregates and are free of secondary deposits.

MICROSCOPIC Several sub-vertical microcracks ranging from 25-50 m (1-2 mil) wide cut from the finished surface to 2-3 mm (80-120 mil) below the finished surface (Figure C5).

4. VOIDS4. VOIDSVOID SYSTEM Concrete is not air-entrained and contains less than 3% air by visual estimation (not determined in accordance with ASTM C457). Occasional water voids were observed (Figure C6).


5. COARSE AGGREGATE5. COARSE AGGREGATE

PHYSICAL PROPERTIES

Crushed limestone with 19 mm ( in.) nominal top size; most particles are 12.5 mm ( in.) across or smaller (Figure C7). The rocks are moderately hard and competent. The particles are sub-equant to oblong in shape with sub-angular to sub-round edges. The grading and distribution is relatively even.

ROCK TYPES

The aggregate consists of limestones that are white to gray to light buff in color. Most of the rocks are bioclastic and grain supported with fine-grained (micritic) matrices. The rocks commonly contain an abundance of fossils and ooids. Occasional micritic limestones contain pellets and evidence of bioturbation.


APPENDIX C: Allen Eagle Stadium Core Petrography Report No. DRP13.1148Sample ID: Core C-3 (17YD6547) Date: 28 December 2013

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PROPERTIES

Natural sand consists of rocks that are hard and competent (Figure C8). The particles are sub-equant to oblong in shape with round to sub-angular edges. The grading and distribution are relatively even.

ROCK TYPES

The sand is mostly siliceous in composition but limestone particles that are consistent with the coarse aggregate make up a minor component of the fine aggregate. The sand contains particles of quartz, quartzite, feldspar and chert. The sand appears to contain more chert than the other samples. Occasional particles of soft, ferruginous (dark red to reddish brown) mudstones that are generally less than 1.18 mm (#16 sieve) across. Some of these components are potentially susceptible to alkali-silica reaction (ASR).

OTHER FEATURESNo deleterious coatings or incrustations observed and no low w/c mortar coatings observed. Reaction rims observed occasionally on chert particles; no other evidence of ASR was observed.


Paste is gray (Munsell 2.5Y/6/1), has a smooth texture and sub-vitreous luster, and is hard (Mohs ~ 4; Figure C9). The paste is gray (2.5Y/5/2) to dark grayish brown (2.5Y/4/2) with a more granular texture and duller luster for up to 2 mm (80 mil) from the top surface.


Fracture surface is gray, has a hackly texture and a sub-vitreous luster. The fracture surface cuts through aggregate particles (Figure C10). No significant secondary deposits were observed on the surface.


PHENOLPHTHALEIN No staining for 2-3 mm (80-120 mil) from the top surface (Figure C11).



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FIGURES

(a)

(b)

Figure C1. Photographs showing (a) oblique view of the top and side of the core with identification labels and (b) the top of the core. The red and blue dots in (a) show the orientation of the saw cuts used to prepare the sample.


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(c)

Figure C1 (contd). (c) Photograph showing the bottom of the core.

Figure C2. Photograph showing the polished surface of the core.


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Figure C3. Photograph showing detail of the top surface of the core; scale in millimeters.

Figure C4. Reflected light photomicrograph of polished surface showing adhesion microcracks and hairline cracks (red arrows) about 12.5 mm ( in.) below the top of the core.


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Figure C5. Reflected light photomicrograph of polished surface showing microcrack (red arrows) at the top of the core.

Figure C6. Reflected light photomicrograph of polished surface showing water voids (red arrows) about 15 mm ( in.) below the top surface.


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Figure C7. Photograph of the polished surface showing coarse aggregate; scale in millimeters.

Figure C8. Reflected light photomicrograph of polished surface showing the fine aggregate.


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(b)

Figure C9. (a) Photograph of polished surface showing overview of paste at the top of the core. The scale is in millimeters. (b) Reflected light photomicrograph of polished surface showing detail of paste texture and luster. The red arrows indicate grains of fly ash.


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(b)

Figure C10. (a) Photograph and (b) reflected light photomicrograph of fresh fracture surface. The scale in (a) is in millimeters.


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(b)

Figure C11. Photographs showing (a) overview of phenolphthalein stained surface and (b) detail of surface near the top of the core. Scale in millimeters in (b).


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PROCEDURES

ASTM C856--Petrographic Analysis The petrographic work was done following ASTM C856 [1] with sample preparation done at DRP in the following manner. After writing the unique DRP sample number on each sample near the received label, the samples were measured and inspected visually and with a hand lens. The orientation of the saw cuts used to prepare the samples was then indicated on each sample with blue and red dots. The samples were then photographed in their as-received condition.

A slab representing a longitudinal cross section of each sample was cut from the central portion of the core using a Diamond Pacific TR-24, a 24-inch diameter oil-lubricated saw. This produced three (3) longitudinal sections for each core. These sections were rinsed in an aqueous solution with a detergent to remove the cutting oil and oven dried overnight in a Gilson Bench Top laboratory oven at ~ 40C (~ 105F) to remove remaining traces of the oil. After drying, each piece was labelled with the appropriate DRP sample number. One piece was set aside for phenolphthalein staining and the other was set aside for thin section preparation.

The central slab was then lapped and polished on a Diamond Pacific RL-18 Flat Lap machine. This machine employs an 18-inch diameter cast iron plate onto which Diamond Pacific Magnetic Nova Lap discs with progressively finer grits are fixed. The Nova Lap discs consist of a 1/16 in. backing of solid rubber containing magnetized iron particles that is coated with a proprietary Nova resin-bond formula embedded with industrial diamonds of specific grit. The slab preparation involved the use of progressively finer wheels to a 3000 grit (~4 m) final polish following procedures outlined in ASTM C457 [2]. An aqueous lubricant is used in the lapping and polishing process. The polished slab from each sample was examined visually and with a Nikon SMZ-1500 stereomicroscope with 3-180x magnification capability following to the standard practice set forth in ASTM C856.

Phenolphthalein was applied to a freshly saw-cut surface from each sample to assess the extent of carbonation, along with thin section analysis. Phenolphthalein is an organic stain that colors materials with pH of greater than or equal to ~ 9.5 purple. Portland cement concrete generally has a pH of ~ 12.5. Carbonation lowers the pH of the paste below 9.5, so areas not stained by phenolphthalein are an indicator of carbonation. The depth of paste not stained by phenolphthalein was measured from each exposed surface.

Petrographic thin sections were prepared by cutting billets from the remaining longitudinal section. Outlines marking the area of the billets were drawn with a marker on the saw-cut surface after visual and microscopical examination of saw-cut and polished surfaces. The billets were labeled with the unique DRP number assigned to the sample and impregnated with epoxy. The impregnated billets

APPENDIX D: Allen Eagle Stadium Core Petrography Report No. DRP13.1148 Procedures Date: 2 January 2014

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1 Standard Practice for Petrographic Examination of Hardened Concrete. Annual Book of ASTM Standards, Vol. 4.02., ASTM C856-13.2 Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete, Annual Book of ASTM Standards, Vol. 4.02, ASTM C457-12.

were then fixed to glass slides with epoxy. After the epoxy cured, the slide was trimmed and ground on a Buehler Petro-Thin device to a thickness of ~ 30 m (1.2 mil). The slide was then moved to a Buehler Beta-Vector machine and polished to a final thickness of ~ 20 m. The grinding and polishing of the thin sections were done in a non-aqueous environment. The thin sections were examined with a Nikon E-Pol 600 petrographic microscope equipped to provide a 50-1000x magnification range following the standard practice set forth in ASTM C856.

APPENDIX D: Allen Eagle Stadium Core Petrography Report No. DRP13.1148 Procedures Date: 2 January 2014

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Proposal

Forensic Engineering, Concrete Distress, and Water Intrusion Consulting Relating to Allen Eagle Stadium

Prepared for Mark Walsh, serving

Prepared by

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Geographic Coverage

Headquartered in Plano, Nelson also operates offices in Austin and Houston, as well as in California, Colorado, Florida, Georgia, Maryland, Maine, and New York.

Scope of Work - Data Collection

Document ReviewOwner Interviews

Data CollectionVisual Observation

Photographic DocumentationGraphical Distress Mapping

To evaluate the reported concrete distress and water intrusion con-cerns at the Allen Eagle Stadium, Nelson will conduct a preliminary review of construction documents for the facility; including plans; specifications; submittals; concrete mix designs, batch tickets, truck reports, and test data; contractors daily reports, architects supple-mental instructions (ASIs), change orders (COs), and other pertinent documentation. Following the preliminary document review, Nel-son will meet with representatives of the owner to present additional questions regarding the project and reported distress, request addi-tional information, and gather further background details.

With information obtained through the above-mentioned process, Nelson will develop and implement an on-site data-collection regime which, at a minimum, will include visual observations of observed conditions, detailed photographic documentation of general conditions, observable distress, and observable areas of water intrusion and detailed graphical mapping of observable ob-served distress and areas of water intrusion. Following processing of the aforementioned data, Nelson will develop a plan for testing the affected concrete materials and exploration of the water intrusion.

Scope of Work - Testing and Analysis

Testing MatrixConcrete Core Sampling

ASTM ExaminationsWater Intrustion Testing

Finish Distress Testing

Concrete testing will involve removal of a number of 4 diameter core samples from distressed and non-distressed sections of con-crete. A testing matrix will be developed and implemented for the material samples, and will likely include comprehensive petro-graphic examination in accordance with ASTM C856, microscopi-cal determination of air content of hardened concrete in accordance with ASTM C457, and unit weight determination in accordance with ASTM C642. Scanning electron microscopy (SEM) with energy-dis-persive x-ray spectrometry (EDX) techniques, as described in ASTM C1723, may also be utilized for materials analysis. Further testing may be necessary based on the analysis of data obtained through the aforementioned testing.

Water intrusion testing will involve water testing and removal of select exterior finishes of areas that indicate water distress. The test-ing protocol will be in accordance to ASTM, AAMA, and/or industry standards as applicable. The testing will be documented photograph-ically and graphically for comparison and analysis to the design and construction documents. Further testing may be necessary in remov-al of select interior finishes based on the analysis and results of the aforementioned testing.

Scope of Work - Findings and Solutions

In-Situ Condition DeterminationParameter Comparison

Verbal and/or Written ReportRemediation Recommendations

Litigation Support

The results of the testing and exploration program will be indicative of the in-situ condition of the tested concrete materials and building assemblies.

Nelson will perform a detailed review of the construction documents to ascertain the design parameters for the affected concrete materi-als and building assemblies, and compare those parameters with the results of the testing and exploration to identify and design and/or construction deficiencies.

Nelson will present its findings verbally to the client and subsequent-ly prepare and deliver a written Report of Findings, if requested.

Additionally, Nelson is capable of providing a remediation solution and construction cost estimate for such remediation.

Finally, Nelson will provide litigation support as necessary.

Primary Experts

Concrete and Materials ExpertArchitecture/Water Intrusion Expert

Cost Estimating Expert

Ryan T. Chancey, Ph.D., P.E., Operations Director Structural Engineer, Materials ExpertDr. Chancey has delivered dozens of presentations pertaining to materials science and concrete to a wide range of audiences; including university fac-ulty, engineering undergraduate and graduate stu-dents, insurance industry representatives, attorneys, and engineering peers. Additionally, Dr. Chancey has authored 10 peer-reviewed publications, includ-ing a chapter in a respected textbook of nanophysics.

Gary S. Dunlap, AIA, NCARB, Technical DirectorArchitectOver twenty years in architectural design and plan-ning, including construction documents and contract administration, architectural document review, and project performance administration. Forensic and analytical architectural project experience includes cause evaluation, cost analysis, and remedial repair for building damage due to construction defects and/or improper design. Timothy J. Lozos, CPE, Technical DirectorCost Estimator/AppraiserCost estimation and analysis of restoration and/or re-medial repair costs to residential, multi-family, com-mercial, and industrial structures that have sustained damage from a gamut of perils.

Concrete Materials Expertise

Concrete Distress ExperienceMaterials Science Experience

Remediation Design ExperienceExpert Witness Experience

preliminary stadium concourse distress evaluation

Documents