Evaluation of coconut shell biochar on recycled aggregate concrete through petrographic studies

Recycled Concrete Aggregate (RCA), derived from discarded concrete, substitutes or stabilizes Natural Concrete Aggregate (NCA) in constructing Recycled Aggregate Concrete (RAC). This study investigates Coconut Shell Biochar (CSB) as a potential mitigator of Alkali-Silica Reaction (ASR) in RAC, particularly in tropical regions like Sri Lanka. CSB, noted for its cost-effectiveness, undergoes assessment for its impact on concrete properties. Petrographic analyses , encompassing optical microscopy and SEM, conducted on CSB-modified RAC in Sri Lanka, reveal favorable mechanical outcomes. Grade 25 RAC, supplemented with CSB, demonstrates 28-day compressive, split-tensile, and flexural strengths of 25.4, 2.5, and 4.1 MPa, respectively. Results indicate CSB effectively alleviates ASR-induced alterations and chemical reactions in RAC, prompting further exploration of CSB's role in controlling specific precipitates and chemical reactions associated with ASR. • There is a demand for recycled aggregate concrete free from alkali Silica reactants. • A need for sustainable solution for alkali silica reaction in recycled aggregate concrete exist. • Petrographic studies show the fractured nature of recycled concrete aggregate. • Coconut shell biochar can reduce secondary alterations and chemical reactions by adsorption. • Finer-size particles of biochar have a high potential for adsorbing secondary materials.