Diagnosis of alkali–aggregate reaction in practice

This is a summary paper focused on the diagnosis of the alkali–aggregate reaction (AAR) in concrete in practice. Rather than broadly attributing a crack to AAR, this paper provides guidance for a practitioner who faces a real concrete structure and must determine whether the crack is being caused by AAR, or drying shrinkage, frost, overloading, sulfate attack or something else. The structure must be allowed to express what has caused its problem. This paper helps to follow a general approach and to look for specific markers to confirm or exclude AAR. Topics covered include first symptoms, desk study, follow-up inspection, structural observations, sample collection, inspection of cores, petrographic examination and additional tests such as scanning electron microscopy, electron probe microanalysis and wet-chemical analysis.