Interpretation of expansion curves of concrete subjected to accelerated alkali-aggregate reaction (AAR) tests

The examination of several long-term expansion results for concretes subjected to accelerated alkali-aggregate reaction (AAR) tests shows that, in some cases, the expansion continues for a long time after AAR has stopped. For these cases, all the concrete swelling is certainly not only caused by AAR, and the continuation of the expansion probably reveals the swelling behavior of concrete when it is conserved in saturated moisture conditions. Considering that this swelling is not negligible compared to the limit expansions fixed by standard AAR tests (2×10⁻⁴ at 90 days for the French performance test), it becomes important to evaluate it in order to avoid the inappropriate rejection of an aggregate.