Assessment of the expansion related to alkali-silica reaction by the Damage Rating Index method

Abstract Among all the quantitative methods that have been proposed for the quantification of the internal deterioration caused by alkali-silica reaction (ASR), the Damage Rating Index (DRI) appears to be one of the most valuable. This paper investigates the correlation between the measured expansion caused by ASR on laboratory-concrete prisms and the damage to concrete, as quantified by the DRI on polished sections prepared from these prisms. New experimental results on the relationships between various petrographic features and expansion levels are provided. Petrographic examinations were also conducted on cores extracted from 35 cm concrete cubes affected by ASR. In this study, the DRI method enables a relatively good estimate of the amount of expansion of concrete prisms made with different aggregates. Results suggest that weighting factors used with the DRI method are appropriate. However, expansion and damage stem from combinations of factors that do not affect aggregates in the same manner. For concrete mixtures incorporating Potsdam sandstone, the most relevant petrograhic feature is the reaction rim surrounding reactive particles. For concrete mixtures incorporating Spratt limestone, almost every petrographic feature (e.g. cracks in aggregate particles and in cement paste) increases consistently with expansion. This study also showed that, in cube specimens made with high W / C ratio and low modulus of elasticity concrete, damage is more severe in the surface zone compared with inner zone. No such difference was observed in concrete cubes of lower W / C ratio higher modulus of elasticity.