This test method allows for the detection of potential alkali–silica reaction (ASR) in aggregates within 21 days. In this chemical test method, aggregates are exposed to 1 N NaOH at four different conditions of CaO content and temperature for 21 days following which a reactivity index (RI) is calculated based on the concentrations of specific ionic species in the liquid phase. The RI measured in each of the four testing conditions is used to classify the ASR reactivity of aggregates.