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The Impact of Coal Combustion Fly Ash Used as a Supplemental Cementitious Material on the Leaching of Constituents from Cements and Concretes
Citation:
van der Sloot, H., D. Kosson, A. Garrabrants, AND J. Arnold. The Impact of Coal Combustion Fly Ash Used as a Supplemental Cementitious Material on the Leaching of Constituents from Cements and Concretes. U.S. Environmental Protection Agency, Washington, DC, 2012.
Impact/Purpose:
Provides summary of available data to help OSWER evaluate any potential environmental impact from the use of fly ash as a supplemental cementitious material on the leaching of constituents from cements and concretes
Description:
The objective of this report is to compare the leaching of portland cement-based materials that have been prepared with and without coal combustion fly ash to illustrate whether there is evidence that the use of fly ash in cement and concrete products may result in increased leaching of constituents of potential concern (COPCs) compared to cement and concrete products that do not contain fly ash. This report evaluates in a new context the leaching results obtained from studies carried out for other purposes, and as such, the observations and conclusions of this report should be considered indicative of performance but not inclusive of the full range of range of possible coal fly ashes used in cement and concrete, usage rates (fly ash can typically be up to 50 wt% of the dry mixture of cementitious materials), or leaching performance of the resulting materials. The broad-based conclusion that the use of coal combustion fly ash in cement materials, for all combinations of fly ash source and usage rate, will not increase leaching of some constituents to levels greater than typical ranges for cement materials not containing fly ash or to levels of environmental concern cannot be reached because of limited range of samples tested. For example, fly ash substitution rates for cement of up to ca. 45 wt% is typical in US large commercial concrete applications, while the predominance of materials reported here have ca. 20-35 wt% fly ash substitution. Based on available data (31 cement mortar and concrete samples containing coal fly ash in comparison to 21 cement and mortar samples that did not contain coal fly ash), results indicate that some (and likely a large portion) of coal fly ashes can be used in cement and concrete formulations without causing a greater range in leaching of COPCs than observed from analogous cement materials not containing fly ash and without causing adverse environmental impacts.