Bunyan Pervious Concrete Roast Some Where, Some Place, In A Desert Near Las Vegas October 2 nd,3rd, and 4 th 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

fly ash void filling CEMENTPARTICLE FLY ASH SPHERES

CHEMICAL PROPERTIES

chemical compounds in pozzolans & portland cement 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.

Fly Ash and Cement Chemistry

ASTM C-618, POZZOLAN

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 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 Rate Cu m/sqm-yr x 10-4 Source: “Bureau of Reclamation Experience with Fly Ash and Other Pozzolans”, Elfert, Ralph J. Jr. Proceedings: Third International Ash Utilization Symposium Bureau of Mines Circular 1974 March 1973

bleed channels FLYASH SURFACE BLEED WATER BLEED CHANNEL ENTRAINED AIR

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 REACTIVEAGGREGATE SURROUNDINGPASTE REACTIVE AGGREGATE EXPANSION

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.

SUSTAINABLE DEVELOPMENT

“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 CO 2 into the atmosphere. Replacing portland cement with fly ash reduces the CO 2 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… 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 CO 2 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 Resource Conservation Recovery Act (RCRA) 1973 Resource Conservation Recovery Act (RCRA) 1980 Bevill Amendment to Resource Conservation and Recovery Act 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 Congress 1988 and 1999 EPA Reports to Congress  Recommended coal ash should not be regulated as hazardous waste 1993 EPA Regulatory Determination 1993 EPA Regulatory Determination  Found regulation as a hazardous waste “unwarranted” 2000 EPA Final Regulatory Determination 2000 EPA Final Regulatory Determination  Concluded 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 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. Approx. 300 acres, several homes, and portions of Emory River affected. TVA clean-up costs publically estimated at over $1 billion TVA clean-up costs publically estimated at over $1 billion Issue: An engineering failure not a question of toxicity. 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.