Title:
Fly Ash Evaluation and Selection for Use in Sulfate-Resistant Concrete
Author(s):
P. J. Tikalsky and R. L. Carrasquillo
Publication:
Materials Journal
Volume:
90
Issue:
6
Appears on pages(s):
545-551
Keywords:
concretes; durability; fly ash; mineral admixtures; pozzolans; sulfate attack; x-ray diffraction; Materials Research
DOI:
10.14359/4428
Date:
11/1/1993
Abstract:
More than 700 concrete specimens were submerged in a 10 percent solution of sodium sulfate for up to 2 years. The expansion, change in mass, and time tofirst cracking were monitored to determine the performance of the concrete exposed to sulfate attack. Several methods of evaluation were investigated to predict the sulfate resistance of concrete containing fly ash. These methods are based on both the bulk chemical composition and on the calculated amorphous glass composition of fly ash. Of the 18 fly ashes used in this study, 9 were ASTM Class F fly ashes and 9 were ASTM Class C fly ashes. In addition, one source of silica fume and one source of blast furnace slag were used. Results show a strong correlation between the chemical and mineralogical composition of a particular source of fly ash and the sulfate resistance of concrete containing that fly ash. Some fly ashes increased the resistance of concrete to sulfate attack, whereas other sources of fly ash accelerated the rate of damage due to sulfate attack. A two-step evaluation procedure is proposed to assist in selecting a fly ash source for concrete that may be exposed to a sulfate environment.