Sulfate Resistance of Concrete Containing Fly Ash

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Title: Sulfate Resistance of Concrete Containing Fly Ash

Author(s): P. J. Tikalsky, R. L. Carrasquillo, and Peter G. Snow

Publication: Special Publication

Volume: 131

Issue:

Appears on pages(s): 255-266

Keywords: bituminous concretes; concretes; C 3A; expansion; fly ash; lignite; sulfates; x-ray diffraction; Materials Research

Date: 3/1/1992

Abstract:
The use of fly ash as a partial replacement for portland cement or as an admixture in concrete may provide many technical and economic advantages if properly utilized. One such technical advantage is to improve the resistance of concrete to sulfate attack. However, this benefit is not realized with all types of fly ash. Some fly ashes have been shown to significantly reduce the sulfate resistance of concrete, others have demonstrated no effect, while still other sources of fly ash improve the durability of concrete in sulfate environments. To clarify the effect of different types of fly ash on concrete exposed to sulfates, a research project is currently being conducted utilizing fly ash from 15 different sources. These fly ashes include sources from bituminous, sub-bituminous, and lignite coal-powered electric generating plants that generally conform to the requirements of ASTM C 618, Class F or C fly ash. The fly ashes are categorized by both chemical and mineralogical phase composition. A Type II portland cement is being used with a fly ash replacement level of 35 percent by volume. The sulfate exposure test consists of concrete cylinders soaking in a 10 percent sodium sulfate solution. Performance is measured by mass loss, expansion, and visual inspection of concrete.