Influence of bio-deposited recycled aggregate on the concrete properties

Recycling construction wastes for their utilisation as aggregates will overcome the dumping and scarcity problems. However, their higher porosity affects the properties of concrete. Hence, this study examines the potential use of microbial-induced calcium carbonate precipitation techniques to improve the quality of recycled coarse aggregates (RCA). The natural coarse aggregate (NCA) was replaced with 50, 100% of RCA and bio-deposited recycled coarse aggregate (BRCA). The aggregate properties were tested and observed that the water absorption and crushing index of RCA were increased by 85.10% and 19.10%, whereas for BRCA, the water absorption and crushing index were increased by only 5.20% and 5.80%. The concrete mixture prepared with optimised and complete percentages of RCA and BRCA was tested for their fresh, hardened, and durable properties. It is observed that the strength of the RAC was 36% lesser than NAC, whereas the strength of the BRAC was 33.40% more compared to the RAC at 28 days. Also, the water absorption and sorptivity of BRAC were reduced by 33.68% and 15.50% and the resistance to carbonation and chloride ingression of BRAC was enhanced by 15.50% and 29.73% when compared to RAC. The microstructural investigations performed through SEM and XRD evident the CaCO₃ precipitation that improves the quality of RCA.