Alkali-Silica Reaction (ASR) in Recycled Aggregate Concrete (RAC) is one of the main challenges in using demolished concrete in construction. Several methods are available to mitigate the impact of ASR, and they have less circular economic potential. This study aims to investigate the possibility of coconut shell biochar (CSB) as an ecofriendly additive to mitigate ASR in RAC. In this investigation, the authors have conducted cement mortar bar test experiments according to the American Society for Testing and Materials (ASTM 1260) standard, Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDS). Studies have
found a higher rate of ASR in recycled concrete aggregate (RCA) compared with natural concrete aggregate (NCA). More importantly, it is found that CSB can adsorb cations (Na+ and K+) that cause ASR in RAC, thereby reducing ASR while not compromising concrete strength.
Hence, the authors concluded that CSB can effectively mitigate ASR in RAC while sequestrating carbon into concrete structures.