Microscopic assessment of recycled concrete aggregate (RCA) mixtures affected by alkali-silica reaction (ASR)

Abstract

Recycled concrete aggregates (RCA) are deemed an efficient approach to reduce waste yet, the presence of previous alkali-silica reaction (ASR) causes reservations towards its use in new construction. In this work, RCA specimens are manufactured in the laboratory incorporating RCA displaying distinct ASR past deteriorations (i.e. slight and severe). The samples are stored in conditions enabling further ASR development and monitored over time. Three levels of “secondary” expansion are selected for analysis, and upon being reached, microscopic evaluations are conducted through the Damage Rating Index (DRI). Results revealed that lower distress is observed in the RCA mixtures when compared to a companion conventional concrete at the same expansion level. Moreover, the damage mechanism of ASR-affected RCA concrete seems dependent on the RCA past deterioration since cracks tend to propagate into the residual cement paste or new cement paste for mixtures made of slightly or severely damaged RCA, respectively.