Evaluation of Fly Ash for Controlling Alkali-Aggregate Reaction

Abstract

Mortar using Pyrex as an aggregate were made using water-binder ratio of 50 percent, replacement ratio of fly ash from 0 to 30 percent by weight and an alkali content of 1.2 percent per weight of cement. Eight fly ashes were used as supplementary cementing materials. These mortars were cured at a temperature of 40 degrees Centigrade and a relative humidity more than 95 percent, and the expansion of these mortars was measured. The concentration of soluble alkali ion in fly ash immersed in the solution containing sodium hydroxide and calcium hydroxide was also determined. By studying effects of physical properties, chemical and amorphous silicon dioxide in fly ash, a method to evaluate the expansion of mortar containing fly ash was proposed based on amorphous silicon dioxide, the replacement ratio and particle diameter of fly ash.