Experimental investigation on strength and durability characteristics of bacteria-based self-compacted concrete with mineral admixtures

This study focuses on self-healing microcrack repair in self-compacting concrete (SCC) by precipitating CaCO3. Five different types of mixes with two distinct cementitious materials, microsilica (MS) and metakaolin (MK), were used as partial replacements for cement. Bacillus Megaterium (BM) was induced by integrating MS and MK to assess the self-healing efficiency of the concrete. Compressive, tensile, and flexural strengths of the concrete and ultrasonic pulse velocity (UPV) were used to assess its effectiveness. The experimental results showed that the compressive strength enhancement in the bacteria-treated microsilica and metakaolin-based SCC mix was 10.08% and 15.20% at 28 days and 5.16% and 9.2% at 56 days compared to the nominal mix. SCCMSBM and SCCMKBM mixes showed ductile behavior under flexural load and increased by 5.55% and 10.52% at 28 days and 5.26% and 10% at 56 days compared to the nominal mix. An increase in strength of 9.16% and 12.37% at 28 days and 5.49 and 13.43% at 56 days was also observed in split tensile strength. The UPV values were reported to be the highest in bacteria-treated microsilica and metakaolin-based SCC mixes at 28 and 56 days, respectively. Further investigation using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) technology confirmed that materials that had been bacteria-treated with an MK-based SCC mix not only last longer but also have significantly higher compressive, tensile, and flexural strengths.