Investigation of coconut shell biochar as an eco-friendly additive to mitigate the alkali-silica reaction in recycled aggregate concrete

Alkali-Silica Reaction (ASR) in Recycled Aggregate Concrete (RAC) is one of the main chal- lenges 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 investi- gate the possibility of coconut shell biochar (CSB) as an eco-friendly 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 con- crete 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 sequestrat- ing carbon into concrete structures.