We encourage building owners to consider the use of high fly ash concrete for foundation replacement and associated foundation projects. We have compiled the following information to inform building owners on the use of this sustainable building material.
High fly ash is made up of minerals and non-combustible materials present in coal and is the main by product of burning coal to produce electricity. Because it is so fine and powdery, it used to “fly” out of the smoke stacks until power plants began collecting it in the 1950’s. The main application for fly ash is concrete, where by reacting with calcium hudroxide (from lime or portland cement), it forms compounds that are actually stronger and more durable than concrete made with pure cement (ACAA/ACC).
Cement production is one of the most energy and resource intensive industrial processes. World wide, it is responsible for 7% of all Carbon Dioxide Emissions. The use of flly ash offers vast environmental benefits. Reducing the demand of one ton of cement would save:
Raw energy: 3200-3500 lbs
Energy: 6.5 million BTU’s (enough energy to power the average american home for 24 days)
Landfill space: equivalent to the amount that the average american uses over a period of 455 days
Air Quality: preventing the harmful emissions of one ton of carbon dioxide – the same amount emitted by a car over a two month period
Three quarters of all fly ash produced each year in the US is disposed of in landfill (TFHRC). If this quantity was instead recycled into concrete, the reduction of carbon dioxide released due to decreased cement production would be the equivalent to eliminating 25% of the world’s vehicles (Headwaters Research).
Although fly ash is cheaper than Portland cement, ground transportation and more controlled placement requirements, if necessary, can negate overall cost savings. At bay area suppliers, high fly ash concrete ranges from no difference in price (Bode Sand & Gravel) to around $10 more per yard (Berkeley-Oakland Ready Mix) than regular suppliers. For a fulll list of suppliers, visit www.buillditgreen.org/guide.
The US Green Building Council encourages high flly ash concrete in its leadership in energy and environmental design (LEED) rating system. High fly ash concrete qualifies for up to 5 different LEED credits for using recycled and local materials for innovation and design. For more information, visit www.usgbc.org.
(ACAA/ACC) American Coal Council and American Coal Ash Association. “Coal ash fact sheet” www.acaa-usa.org
Headwaters resources “Fly ash and the environment” 2005 www.flyash.com/flyashenvironment.asp
(TFHRC) Turner-Fairbank Highway Research Center. United States Department of Transportation – Federal Highway Administration. “Coal fly ash: Material description.” www.tfhrc.gov/hnr20/recycle/waste/cfa51.htm