Coal Combustion Products: American Coal Ash Association Presents
Geotechnical Uses for CCPs David Goss Executive Director American Coal Ash Association
Coal Ash vs. CCPs Coal combustion products are residuals from the combustion of coal and emission control systems: – Fly ash – FGD (synthetic) gypsum – Bottom ash and boiler slag – Air emission control system residues (other FGD co-products) “Coal Ash” and “CCPs” have been terms used interchangeably; CCPs now apply to both ash and FGD byproducts
Fly Ash Fine particles like flour or talc Exhibits “pozzolanic” characteristics – Siliceous or siliceous and aluminous materials, when in the presence of water, react with calcium hydroxide to produce cementitous properties Besides natural ash, there are two types – Class F from bituminous coal (lignite?) – Class C from sub-bituminous coal (lignite?)
What Makes Fly Ash Useful? Non-hazardous nature Mineralogical and pozzolanic characteristics allow it to be used in lieu of other natural materials Spherical shape Easily transportable Can be conveyed dry or in moistened form
Fly Ash Benefits Additive to concrete as a replacement for portland cement – Enhances durability – Reduces permeability – Improves workability Makes good concrete better Potential economic savings at time of placement and through life cycle
Bottom Ash Heavier than fly ash and granular in nature. Can be used: – as raw feed for cement production – in soil applications to improve drainage and blended with other materials for composting – in masonry blocks and concrete products – in road base and mineral fillers in asphalt – as a component of artificial aggregates
Structural Applications Highway overpasses, embankments, railroad realignments and new track work; also in mining Serves as low-cost material that be blended with available borrow materials Standards & guidelines established by ASTM International & others Large volumes of CCPs can be used
Structural Fill Guidance Information ASTM E2277-03 addresses: – Engineering properties and behavior of CCPs – Testing procedures – Design considerations – Construction techniques Technical information and Case studies can be found at: http://www.epa.gov/epaoswer/osw/conserve/c2p2 – Recycled Materials Resource Center
Some Examples of Large Projects
Rostraver Airport, Pennsylvania Interstate 76/270 - Denver, CO Crites Field Waukesha, WI Jackson County, Missouri Phoenix links, Pennsylvania Interstate 279 – Pittsburgh, PA Washburn Airport, North Dakota Asphalt rehabilitation - Delaware and Warren counties, Ohio
Soil Stabilization Fly ash alone (Class C) or with portland cement, CKD or lime can b used to modify soils – To dry wet working areas – To increase stiffness – Reduce permeability – Reduce plasticity and swelling – Control compressibility and moisture Typically more economical than just portland cement
Stabilization Guidance
ACAA’s Soil Stabilization manual Iowa State work funded by FHWA University of Wisconsin – Madison TxDOT State of Missouri Various conference proceedings DOE funded research University of North Dakota studies Recycled Materials Resource Center
Environmental Benefits of CCPs
Reduces greenhouse gas emissions Conserves natural resources Reduces energy impacts of extraction and processing Cuts down on need for landfill space
Outreach and Partnerships Wide dissemination of accurate information Joint industry and government information exchange partnerships Face to face technology transfer Collaborative relationships among organizations with allied interests
Green Highway Partnership Public-Private sector “Green Highway Forum” – Environmentally sensitive context for planning, design. Construction and maintenance of roadways – Use and reuse of industrial materials, biofuels, minimize impact on land Being developed by industry, EPA, FHWA, AASHTO, AGC, etc. www.greenhighways.org
Publications “Soil Stabilization and Pavement Recycling with Self-Cementing Coal Fly Ash” (ACAA) “Fly Ash Facts for Highway Engineers” (FHWA) Using Coal Ash in Highway Construction: A Guide to Benefits and Impacts” (US EPA) “Leaching of Heavy Metals from Fly Ash Stabilized Soils Used in Highway Pavements” (DOE-CBRC) “In Situ Stabilization of Gravel Roads with CCPs” (DOE CBRC)
More Publications “User Guidelines for Waste and By-Product Materials in Pavement Construction” (FHWA) “Fly Ash Soil Stabilization for Non-Uniform Subgrade Soils” (FHWA) “Guidelines for Modification & Stabilization of Soils and Base for Use in Pavement Structures” (TxDOT) “ASTM 2277-03 – Standard Guide for Design and Construction of Coal Ash Structural Fills” “High Volume Fly Ash Utilization Projects in the US and Canada” (EPRI)
Web Links American Coal Ash Association: www.acaa-usa.org United States Environmental Protection Agency, Office of Solid Waste: http://www.epa.gov/epaoswer/osw/conserve/c2p2/ University of Kentucky Center for Applied Energy Research International Ash Utilization Symposium Ash Library: http://www.flyash.info University of North Dakota EERC Coal Ash Resources Consortium: http://www.eerc.und.nodak.edu/carrc/index.html University of Wisconsin Milwaukee Center for By-Products Utilization: http://www.uwm.edu/Dept/CBU West Virginia University Combustion Byproducts Recycling Consortium: http://wvwri.nrcce.wvu.edu/programs/cbrc/index.cfm
Conclusions CCPs can be used safely and in lieu or other natural materials in many applications There may be some economic advantages to using fly ash and/or bottom ash Technical guidance and many assessments of environmental impact are available from academic and regulatory sources
Conclusions CCP use directly supports and contributes to a more sustainable environment Sound technical, environmental and operational procedures can address perceptions and potential objections Properly managed applications will achieve desired physical, environmental, economic and social results
Coal Combustion Products: Geotechnical Uses for CCPs
Thank You
David Goss Executive Director American Coal Ash Association 720-870-7897