Evaluation of Fly Ash in Portland Cement Concrete Paving in Woodbury County, Iowa, Final Report, HR-201, 1980

The earliest overall comprehensive work on the use of fly ash in concrete was reported by Davis and Associates of the University of California in 1937. Since that time, there have been numerous applications of the use and varying propertions of fly ash in portland cement concrete mixes. Fly ash is a pozzolanic powdery by-product of the coal combustion process which is recovered from flue gases and is, generally associated with electric power generating plants. Environmental regulations enacted in recent years have required that fly ash be removed from the flue gases to maintain clean air standards. This has resulted in an increased volume of high quality fly ash that is considered a waste product or a by-product that can be utilized in products such as portland cement concrete. There are several sources of the high quality fly ash located in Iowa currently producing a combined total of 281,000 tons of material annually.