New Chemical Reactivity Index to Assess Alkali–Silica Reactivity

Abstract

Despite the awareness of the alkali–silica reaction (ASR) since 1940, the need for an efficient and reliable method of evaluating the potential reactivity of aggregates for use in concrete still exists. Current standards to assess the ASR susceptibility of aggregates have limitations due to inherent problems with accelerated testing conditions. This paper introduces a novel chemical reactivity index (RI) to evaluate the alkali–silica reactivity of coarse aggregates or concrete mixtures by exposing samples to a simulated pore solution with composition mimicking that expected in the concrete. Based on the mix design to be evaluated, aggregate samples are exposed to an alkaline solution of appropriate concentration and fixed amounts of CaO. The newly proposed alkali–silica RI is calculated based on the concentrations of silicon, aluminum, and calcium in solution after 21 days of exposure at 55°C. This RI, sensitive to alkali concentration and aggregate mineralogy, exhibited strong agreement with physical expansion.