Recycled concrete aggregates (RCA) have been adopted as one of the most efficient methods to reduce the carbon footprint of the concrete industry. However, the performance of recycled concrete mixtures made of Alkali-silica reaction (ASR)-affected RCA is primarily unknown. In this work, two types of RCA were produced from ASR-affected concrete with distinct levels of deterioration (i.e., slight and severe). Three levels of secondary damage (i.e., expansion levels of 0.05%, 0.12%, and 0.20%) were selected and evaluated through the direct shear test. Results revealed that RCA concrete’s shear strength depends on the severity of the RCA’s past deterioration. Moreover, the performance of the concrete specimens subjected to direct shear are in accordance with the cracks features formed in the microstructure of the recycled concrete as a function of ASR-induced secondary expansion observed through the damage rating index (DRI).

The damage rating index (DRI) has proven to be a quite reliable microscopic technique enabling the condition assessment of concrete affected by internal swelling reactions. Yet, very little research has been conducted on the use of the DRI to appraise induced deterioration caused by physical salt attack (PSA) and external sulfate attack (ESA). This study aims to assess the condition of concrete subjected to different salt solutions (i.e. sodium sulfate (Na₂SO₄), sodium chloride (NaCl), seawater and limewater), and exposure conditions (i.e. partially and fully immersed) through the DRI. Concrete specimens displaying two distinct water/cement ratios (i.e. 0.45 and 0.65) were manufactured and exposed to the above salt solutions for 12 months. Then, the samples were removed from the exposure conditions and prepared for microscopic analysis. The DRI was shown to be an effective technique to assess the condition of PSA- and ESA-affected concrete since different degrees of damage and features were captured for the various exposure conditions studied.