Fly Ash Looms As The ‘New Asbestos’
...spill was obviously an environmental catastrophe, but it appears some officials are casting too wide a net to address this incident,” says Claude Goguen, director of technical services at the National Precast Concrete Association, Carmel, Ind.
In 1993 and 2000, EPA determined CCBs did not warrant management as hazardous waste. Last October, EPA delivered its proposed rule to the Office of Management and Budget for interagency review and comment. The proposal is still in the hands of OMB, with no indication of when its review will be completed. EPA said in a statement, “This rule continues to be under review, and we expect to issue a proposed rule in the near future.”
The nonprofit American Concrete Institute (ACI), which publishes technical standards, has concerns about EPA’s proposed rule. Of some 400 standards and technical documents, 106 would have to be revisited were fly ash ruled to be a hazardous waste. These standards include ACI 232, which outlines the use and application of fly ash, and ACI 318, the model concrete code.
“Even if it is a hybrid ruling, we would need to evaluate the impact on applications and our documents,” says Florian Barth, ACI’s 2009-10 president and a consultant based in Los Gatos, Calif. Document review could take several years, he says, because ACI relies on its member volunteers to develop its standards.
In 2008 in the U.S., 136 million tons of CCBs were produced, according to a survey by the American Coal Ash Association (ACAA). Almost 16 million tons were used in cement and concrete production. Another 8.5 million tons went into the production of wallboard products. The use of fly ash instead of portland cement, which is an energy-intensive product, avoided 12 million tons of carbon dioxide emissions, says ACAA.
vice president of regulatory affairs Portland Cement Association
In the U.S., fly ash use in concrete ramped up beginning in the 1980s. Since 2000, the recycling rate for CCBs has increased to 44% from 30%, says ACAA. During that time, more than 1.1 billion tons of CCBs were produced, with 430 million tons recycled. In the U.S., CCBs are the second-largest waste stream after municipal solid waste, says ACAA.
Use of fly ash in concrete is considered environmentally responsible because it typically replaces 15% to 25% of the cement content in concrete, depending on the specific mix for a specific project. That, in turn, reduces the carbon dioxide generated in cement production. In 2007, there was a 15-million-ton reduction of CO2 production, says ACI.
Fly ash makes concrete less permeable, which reduces infiltration of water and aggressive chemicals. The material resists unwanted alkali-aggregate and sulfate reactions, says ACI. It also increases concrete’s compressive strength, improves the workability of fresh concrete and reduces heat of hydration in mass concrete.
Fly ash is recognized by the LEED rating system as a postindustrial recycled material. “We respect EPA’s ability and role as a regulator … and are quite sure there is alignment around the beneficial use of fly ash,” says Horst. However, “if EPA designates fly ash as a hazardous waste, LEED committees will take a look at the rating system.”
