Effect of starch-based admixtures on the exothermic process of cement hydration

Abstract

The effect of three types of starch-based admixtures, namely glucose and its derivatives, soluble dextrin with various degree of polymerization and a novel starch-based temperature rise inhibitor (TRI) with various degree of starch acidification on the exothermic process of cement hydration has been investigated through the calorimetry measurements. Except delaying the appearance of the main hydration peak as the retarding effect, starch-based admixtures can also reduce the heat flow during the acceleration period and induce a lower maximum heat flow as the depressing effect. Together with the dissolution and adsorption results, it can be concluded that the relationship between these two effects is determined by the action time of molecule in the cement paste. The soluble admixtures with fairly short action time focus mainly on disturbing the cement hydration during the induction period but have minor effect on depressing the main hydration peak. TRI with limited dissolution can persistently inhibit the cement hydration over a longer period of action time, inducing negligible retarding effect but apparent depressing effect.