The purpose of this phase is to evaluate the past, current and future trends of use of fly ash in concrete and restrictions to its use. The American Coal Ash Association (ACAA) conducts an annual survey of fly ash production and use. Typically on an annual basis out of the 70 million tons of fly ash generated, about 40% is beneficially utilized. Out of the fly ash that is beneficially used about 50% is used in cement and concrete applications. Table a has been developed based on fly ash use as reported by ACAA, slag cement use as reported by the Slag Cement Association and cement use as reported by the US Geological Survey.
Ready mixed concrete production is estimated from cement shipments reported by USGS. Several other assumptions as stated in Table 1a are made to derive the fly ash volume used in ready mixed concrete. Table 1a shows that even though concrete volume had decreased, fly ash and fly ash+slag cement use had steadily increased and stood at 12% and 16% respectively of the total sententious content in 2008. These percentages should not be confused to percent of cementitious materials used in typical concrete mixtures.
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