CAPITAL PROJECTSINVOLVING CONCRETE

S. Ebow Coleman, Ph.D., P.E.President, C3S, Inc.

S. E. Coleman, C3S, Inc., - 2 -

Concrete – A Global Construction Material

Source: http://www.aed.usace.army.mil/fullphoto.asp?Link=photos/AT-Bridge-052.jpg&PhotoID=39U.S. Army Corps of Engineers - Afghanistan Engineer Project

Construction on the Afghanistan-Tajikistan Bridge

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Concrete – A Global Construction Material

Three Gorges Damacross the Yangtze River,

China

Source: http://www.internationalrivers.org/en/image/tid/111

Source: DigitalGlobe

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Concrete – A Global Construction MaterialConstruction Site in Mecca, Saudi Arabia

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Concrete – A Global Construction Material

Joina Centre,Harare, Zimbabwe

Source: www.skyscrapercity.com

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Capital Project

• Requires skilled and trained personnel

• Huge capital outlay

• Often takes several months or years

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Concrete: Ingredients

• Portland cement• Gravel/Crushed rock• Sand• Water• Mineral admixture• Chemical admixture• Others

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Types of Portland Cement andTypes of Portland Cement andTheir Phase CompositionsTheir Phase Compositions

11-1311-133-53-535-3735-3742-4442-44Sulfate ResistantSulfate ResistantV.

12-1412-144-64-645-4745-4729-3129-31Low HeatLow HeatIV.

7-97-911-1311-1314-1614-1655-5755-57High Early StrengthHigh Early StrengthIII.

11-1311-135-75-728-3028-3045-4745-47Modified GeneralModified GeneralPurposePurpose

II.

7-97-95-135-1324-2624-2648-5048-50General PurposeGeneral PurposeI.

CC44AFAFCC33AACC22SSCC33SS

Potential Compound Composition %Potential Compound Composition %GeneralGeneralDescriptionDescription

Type ofType ofCementCement

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Cement Clinker

C3S

C2S

C3A

C4AF

Phasecompositionsidentified byshapes

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Portland Cement –What to look out for

• MgO

• Total Alkali– High Alkali Cement– Low Alkali Cement

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Potential Issues in Capital Projects

• Coarse & Fine Aggregates• Environmental Effect on Concrete

Degradation• Incompatible Materials• Vague Specification• Mineral Admixtures• Chemical Admixtures

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Coarse & Fine Aggregates

• Constitute 65-75% by volume ofconcrete

• Weathered aggregates• Reactive aggregates

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Coarse & Fine Aggregates

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Concrete Failures:Sulfate Attack

Environmental Effect onConcrete Degradation

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Incompatible Materials

• Reactive Aggregates• High Alkali Cement• Moisture

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Vague Specification

A damaged wastewater tank (three years old)

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Vague Specification (continued)

• Type I/II Cement

• Type I: C3A ~ 5-13%• Type II: C3A ~ 5-7%

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Mineral Admixtures• Natural Pozzolans, e.g. volcanic ash• Fly ash, silica fume• Reactive silica is key ingredient

Basic Pozzolanic Reaction: 2 StepsBasic Pozzolanic Reaction: 2 Steps

Cement + H2O C-S-HC-S-H + Ca(OH)2 +

Mineral Admixture (SiO2)

C-S-HC-S-H

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Mineral Admixtures

• Excess causes surface defects

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Mineral Admixtures

Effervescenceon wall ofdam – absenceof mineraladmixture

Source:www.SkagitTours.com

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Chemical Admixtures• Retarders• Accelerators• Water reducers• Superplasticizers• Air-entraining agents• Others

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Chemical Admixtures

• Plant manufacturing structuralmembers

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Chemical Admixtures

• Inadvertent dosagecaused excessentrained air

• Lower thanspecifiedcompressive strength

• Several structuresrejected

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What is needed on a capitalproject?

• Consistent monitoring of materials– Project Planning Phase– Construction Phase

• Quality Control of Completed Structures• Knowledgeable and experienced

engineers

CAPITAL PROJECTSINVOLVING CONCRETE

S. Ebow Coleman, Ph.D., P.E.PresidentC3S, Inc.

QUESTIONS & ANSWERS