Most people wouldn’t find a magazine titled Ash at Work to be all that scintillating—I guess that makes me a concrete nerd, because I found the most-recent issue fascinating. I’ve wondered for the past year or so since the EPA finally agreed that fly ash should not be classified as hazardous waste, whether there’s really enough available if its use in concrete increased significantly. We’ve all heard about the phasing out of coal-fired power plants, so where will the ash come from?
A new report from the American Coal Ash Association tries to answer that question with assurances that even under the most aggressive phase-out there would still be plenty of coal power being used to fill the need for ash. (To read the report, click here, open the current issue then go to the table of contents and click on the very last story, First Ever Ash Production and Use Forecast.) The other thing I found interesting in Ash at Work was articles describing the new technologies being developed to remove carbon and mercury from fly ash. Apparently activated carbon is used in the flue gas cleaning process to remove mercury and that ends up in the fly ash. But high carbon fly ash consumes air-entraining admixtures in concrete and also people don’t want mercury in their concrete.
Luckily, with the increasing use of fly ash and its increasing value, the electrical utilities and others are finding ways to clean up the ash to where now even old ash in landfills is being excavated and prepared for use in concrete. In some cases, with regional variations in availability, to get acceptable ash may require it to be shipped significant distances. Of course none of this is free, but with the improved performance of concrete with fly ash, the benefits should outweigh the costs.
Fly ash isn’t right for every application, but in the majority of cases there is a performance improvement and that doesn’t even count the positive outcomes for the environment in using what would otherwise be dumped into landfills. Look for more fly ash in your future!