Chemical and Physical Sulfate Attack on Fly Ash Concrete Mixtures

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Title: Chemical and Physical Sulfate Attack on Fly Ash Concrete Mixtures

Author(s): Rajaram Dhole, Michael D. A. Thomas, Kevin J. Folliard, and Thano Drimalas

Publication: Materials Journal

Volume: 116

Issue: 4

Appears on pages(s): 31-42

Keywords: fly ash; silica fume; sulfate attack; ultra-fine fly ash (UFFA)

Date: 7/1/2019

Abstract:
Fly ash concrete mixtures were tested for the chemical and physical sulfate attack. Concrete mixtures consisting of ratios of fly ashes, Type I cement, silica fume, and ultra-fine fly ash (UFFA) were tested. Four exposure conditions were simulated by subjecting the concrete specimens to: 1) immersion in 5% Na2SO4 solution; 2) wet-dry cycling in 5% Na2SO4 solution at 23°C (73°F, wet) and 38°C (100°F, dry); 3) immersion in saturated CaSO4 solution; and 4) wet-dry cycling in saturated CaSO4 solution at 23°C (73°F, wet) and 38°C (100°F, dry). Control specimens were stored in water at ambient temperature. Performance of the concrete mixtures was studied through visual inspection and by monitoring the changes in mass, length, and dynamic modulus of elasticity over time. It was found that improved sulfate resistance can be provided to the fly ash concrete by controlling water-cement ratio (w/c) and blending with Class F fly ash, UFFA, and silica fume.