Laboratory Assessment of the Potential Rate of ASR Expansion of Field Concrete

In-situ monitoring of concrete deformations and movements is the best way to assess the current expansion of concrete members affected by alkali-silica reactivity (ASR). However, laboratory tests on cores are less expensive and more rapid, and are commonly used to assess the potential for further expansion due to ASR. The risk of expansion and damage due to ASR can be reasonably assessed in the laboratory from: (1), the inherent expansivity of the concrete under study, which is determined by testing core samples in air at 100% RH and 38°C; (2), the residual absolute reactivity of the aggregates present in the concrete under study, which can be determined by testing core samples in 1N NaOH solution at 38°C or, even better for coarse aggregates, by testing aggregates extracted from cores through the concrete prism test CSA A23.2-14A or ASTM C 1293; (3), the amount of alkalies that are still active in the concrete, i.e. in the pore solution, which is estimated by a hot-water extraction method on ground concrete, and (4), humidity, (5), temperature, and (6), stress conditions (confinement, reinforcement, pretensioning, postensioning) in service. The individual risk indices corresponding to each of the above parameters are combined to determine the potential rate of ASR expansion of concrete members in service, either already affected by ASR or not.