Fly Ash Concrete Fly ash is a waste product of the combustion of
coal. It is produced at coal-fired power plants and blast
furnaces. It may be substituted for as much as 35% of the cement
in some concrete mixes. Its use has been widespread in very
large projects for many years, however smaller local concrete
suppliers are now beginning to offer it more routinely. For each
pound of fly ash used instead of cement, one pound of carbon
dioxide emissions will be saved. A concrete floor slab for a
typical two-car garage would contain approximately 4,000 lbs. of
cement; therefore substituting 25% fly ash would save 1,000
pounds of carbon dioxide. This is equal to the emissions from an
average automobile for one full month! Using the 1,000 pound of
fly ash will save enough energy to power the average American
home for 12 days, and save enough landfill space for the solid
waste generated by an average American for over 200 days!