Bunyan Pervious Concrete RoastSome Where, Some Place, In A Desert

Near Las VegasOctober 2nd,3rd, and 4th 2012

Chris Bedford Headwaters Resources

Objectives

Understand the Chemical and Physical Contributions Fly Ash Provides to Concrete and discuss the differences in Class “C” and Class “F”

Sustainability and Green Building incentives Discuss concerns of environmental issues and

possible new regulations by the EPA. Demo project using Class “F” ash and white silica

fume

Fly Ash Magnification

PHYSICAL PROPERTIES

CHEMICAL PROPERTIES

chemical compounds in pozzolans & portland cement

Major chemical compounds found in Portland cement also found in pozzolans but the ratios and contents are different.

Cement has large amount of CaO (~65%) Class F fly ash is low in CaO (<15%) Class C higher in CaO (~ 28%) The high relative SiO content in fly ash reacts with

CaO in Portland cement to produce the same calcium silica hydrates, thus improved strength production.

Chemical Compounds

Fly Ash Class F

Cement

CaO 6.90 64.40 SiO 57.2 22.60

Al2O3 22.3 4.30 Fe2O3 4.90 2.40 MgO 1.80 2.10 SO3 0.65 2.30

Na2O & K2O 0.60 0.60

Fly Ash and Cement Chemistry

ASTM C-618, POZZOLAN

F C N F C NChemical Optional Physical

SiO2 + Al2O3 + Fe2O3 min % 70 50 70 Multiple Factor 225 - - SO3 max % 5 5 4 Inc. in Drying Shrinkage max % 0 0 0 Moisture Content max % 3 3 3 Uniformity Requirements Loss on Ignition max % 6 6 10 A.E. Admixture Demand max % 20 20 20

Control of ASRPhysical Expansion, % of Low Alkali Cement max % 100 100 100

Fineness + 325 Mesh max % 34 34 34 Sulfate Resistance Strength Activity/Cem. min % 75 75 75 Moderate Exposure, 6 Months max % 0.10 0.10 0.10 Water Requirement max % 105 105 115 High Exposure, 6 Months max % 0.1 0.1 0.1 Autoclave Expansion max % 0.8 0.8 0.8 Uniformity Requirements

Density Max Variation max % 5 5 5Fineness Points Variation max % 5 5 5

Hydration products of cementing binders

STRENGTH PERFORMANCE

Increased Strength

Fly ash chemically combines with free lime to form additional CSH.

Result is long-term strength gain greater than conventional portland cement concrete.

TYPICAL COMPARISON OF COMPRESSIVE STRENGTH

0100020003000400050006000700080009000

3 7 28 56 90 180 365

CompressiveStrength

(PSI)

Source: Bureau of Rec. Experience

Age (Days)

Plain Cement

PSIGain

(Insurance)20 % Fly Ash

Permeability

Fly ash concrete typically requires less water for the same level of workability in the field.

Less water creates finer and fewer bleed channels in concrete.

Fly ash reacts with the excess free lime from cement to create additional binder that over time “corks up” the existing bleed water channels, reducing permeability.

Permeability rate fly ash concrete vs. conventional concrete

Permeability RateCu m/sqm-yr x 10-4

Source: “Bureau of Reclamation Experience with Fly Ash andOther Pozzolans”, Elfert, Ralph J. Jr.Proceedings: Third International Ash Utilization SymposiumBureau of Mines Circular 1974 March 1973

ASR & Sulfate Attack

ASR is caused by reactive aggregates in contact with the alkalis in portland cement

Sulfate attack is the result of high sulfate soils reacting with the cement paste.

Replacing cement with Class F fly ash can help mitigate both ARS and Sulfate Attack.

Some other fly ashes may actually accelerate either reaction, so testing is appropriate.

alkali silica reaction

REACTIVE AGGREGATE

SURROUNDINGPASTE

REACTIVE AGGREGATEEXPANSION

Heat of Hydration Concrete elements with minimum cross-sectional

dimensions of two feet or more may have extreme thermal differentials between the core and the rapidly cooling surface while curing.

Heat differentials can cause cracks, crazing. Reducing the core temperature reduces the heat

differential. Replacing cement with fly ash can reduce the heat of

hydration in concrete. For every percent of cement you reduce, the heat of

hydration is reduced by one-half percent.

SUSTAINABLEDEVELOPMENT

“The Fly Ash Revolution: Improving

Concrete Quality”

U.S. Green Building Council The USGBC promotes the classification and use of

building materials containing recycled products. Environmentally conscious owners and government

officials require LEED™ points on new building projects. “LEED Green Building Rating System” assigns point

values to green building practices. Fly ash qualifies for:– Recycled content materials credit– Locally produced materials credit– Innovative use credit for high volume applications

CA Green House Gas Reduction Act

Assembly Bill 32 Cement industry on the early action list Objective: Replace more than 25% of Portland

cement with pozzolans Effects both public and private construction Full implementation by 2013

Sustainable Development

The use of fly ash in concrete reduces the impact on limited landfill space.

The production of every ton of portland cement contributes about one ton of CO2 into the atmosphere. Replacing portland cement with fly ash reduces the CO2 load on the environment.

The improved long term strength and durability of fly ash concrete reduces the lifecycle cost.

Environmental Benefit

For every ton of fly ash used… Enough energy is saved to provide electricity to

an average American home for 24 days. The landfill space conserved equals 455 days of

solid waste produced by the average American. The reduction in CO2 emissions equals 2 months

of emissions from an automobile.

California Green Building Code

Requires that recycled materials be used in all concrete– Fly Ash– Slag– Silica Fume

Effective in 2013 compliance in 2012 is voluntary The code applies to all construction, public and

private

Coal Ash Regulatory History

36

1973 Resource Conservation Recovery Act (RCRA)1980 Bevill Amendment to Resource Conservation and Recovery Act

Instructed EPA to "conduct a detailed and comprehensive study and submit a report" to Congress on the "adverse effects on human health and the environment, if any, of the disposal and utilization” of coal ash

1988 and 1999 EPA Reports to CongressRecommended coal ash should not be regulated as hazardous waste

1993 EPA Regulatory DeterminationFound regulation as a hazardous waste “unwarranted”

2000 EPA Final Regulatory DeterminationConcluded coal ash materials “do not warrant regulation [as hazardous waste] ”

and that “the regulatory infrastructure is generally in place at the state level to ensure adequate management of these wastes”

Kingston Power Plant Impoundment Failure

37

December 22, 2008, failure of containment dike released 5.4 million cubic yards (approx. 1 billion gallons) of ash slurry

Approx. 300 acres, several homes, and portions of Emory River affected.

TVA clean-up costs publically estimated at over $1 billion

Issue: An engineering failure not a question of toxicity.

Where the Science Stands

38

Coal ash does not qualify as hazardous waste based on its toxicity characteristics

Kingston damage case related to engineering failure, not the material involved

No damage cases related to beneficial use of coal ash

Significant demonstrated beneficial use benefits– Environmental– Performance– Economic

Jim Bridger

Latest cutting edge technology in pervious concrete using secondary cementitious materials – 20% Class “F” fly ash and 5%” “white” silica

fume.

Art work on pavement is done with colored soy bean oil that contains no VOC’s. Pavement design by David Mitchell of Bunyan Industries.

The pervious concrete was a natural select for the rustic appearance for the home.