Title:
Sulfate Resistance of Mortar Mixtures of High-Calcium Fly Ashes and Other Pozzolans
Author(s):
Rajaram Dhole, Michael D. A. Thomas, Kevin J. Folliard, and Thano Drimalas
Publication:
Materials Journal
Volume:
108
Issue:
6
Appears on pages(s):
645-654
Keywords:
Fly ash; silica fume; sulfate resistance; ultra-fine fly ash.
DOI:
10.14359/51683468
Date:
11/1/2011
Abstract:
Ternary and quaternary mixtures of six Class C fly ashes and other pozzolans, such as Class F fly ash, silica fume, and ultra-fine fly ash (UFFA), were tested for sulfate resistance as per the ASTM C1012/C1012M-10 procedure over 18 months. The resistance of the ternary mixtures improved with increasing amounts of Class F fly ash. A clear relationship between the performance of fly ash mixtures in the ASTM C1012/C1012M-10 test and the calcium content of the fly ash mixture was observed. This relationship appears to hold for blended mixtures of both Class F and Class C fly ashes. Silica fume, even at small percentages, was found to significantly reduce the expansions of all mixtures. Substantial reductions in expansions were observed when silica fume or UFFA were used in sufficient quantity along with the Class C fly ashes. Selected mixtures were scrutinized by scanning electron microscopy (SEM) for changes in microstructure.