Effect of Fly Ash Composition on Sulfate Resistance of Cement


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Title: Effect of Fly Ash Composition on Sulfate Resistance of Cement

Author(s): P. K. Mehta

Publication: Journal Proceedings

Volume: 83

Issue: 6

Appears on pages(s): 994-1000

Keywords: blended cements; calcium; cement pastes; ettringite; fly ash; sulfate resistance; x-ray diffraction.

Date: 11/1/1986

A laboratory investigation involving 16 fly ash samples of varying calcium content was undertaken with the objective of further clarifying the relationship between fly ash composition and sulfate resistance. A Type I portland cement was used to prepare blended cements containing 25 or 40 percent fly ash by weight. The resistance to sulfate attack was evaluated by immersion of well-cured neat cement paste specimens in a standard sulfate solution for a given period and by determining the strength loss as a result of sulfate exposure. The results show that rather than the chemical composition or the R-factor of a fly ash, it is the mineralogical composition of the cement-fly ash interaction product that controls the sulfate resistance.