FLY ASH EVALUATION AND SELECTION FOR USE IN SULFATE-RESISTANT CONCRETE

Over 700 concrete specimens were submerged in a 10% solution of sodium sulfate for up to 2 years, and the performance of the concrete exposed to sulfate attack was determined. Several methods of evaluation were investigated to predict the sulfate resistance of concrete containing fly ash. The 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 2-step evaluation procedure is proposed to assist in selecting of fly ash sources for concrete that may be exposed to a sulfate environment.