Effect of MICP-treated recycled coarse aggregates and banana fibres on the self-healing and flexural property restoration

The elevated water absorption and reduced strength of recycled concrete aggregates constrain their utilization in building materials. Bacillus megaterium (MTCC-1684) exhibits significant potential for microbial-induced calcium carbonate precipitation (MICP), an eco-friendly technique that improves the weaker regions of recycled coarse aggregates (RCA), reduces hydrophilicity and enhances the tensile strength of banana fibre (BF). The primary objective is to investigate the efficiency of bacterially treated banana fibre (TBF) and bacterially treated RCA as carriers for bacterial spores in banana fibre recycled aggregate self-healing concrete (BFR-SHC). The results revealed that MICP significantly improved water absorption and bulk density of 50 % RCA by 46.8 % and 9.8 %, respectively, through calcite deposition on surfaces and pores > 0.2 mm. The healing efficiency with 50 % TRCA and 2 % TBF was more pronounced in the recovery of flexural properties and the trends were found as BF2R50 >, BF1R50 > BF1R100 >, BF2R100. Notably, the maximum flexural toughness efficiency index (η) increased from 1.04 to 1.09 in BF2R50. The incorporation of bio-treated RCA and BF accelerated fibre-matrix regeneration and crack sealing through calcite precipitation, restoring flexural properties. Morphological analysis of BFR-SHC showed that regenerated calcite at the fibre-matrix interface consisted of rhombohedral and vaterite formed after a 56-day healing incubation period. The findings encourage concrete engineers to adopt bacterial self-healing mechanisms for the development of eco-friendly solutions for sustainable construction practices.