Comparative Analysis of Bacterial Concrete (PPC M40 Grade with Bacillus subtilis) and Conventional OPC Concrete

Concrete’s lifespan decreases when cracks form, which is a common issue regardless of mix design. Self-healing concrete, utilizing microbiologically induced calcium carbonate precipitation, aims to prevent structural damage caused by cracks. This process allows controlled material passage while maintaining structural integrity. This concrete type can autonomously initiate biological activity and perform self-repair. In our study, we explored the impact of Bacillus Subtilis bacteria on PPC M40-grade concrete. We compared Ordinary Portland Cement (OPC) with Bacteria-Stimulated PPC concrete of the same grade. Bacillus subtilis bacteria were introduced to the PPC concrete in varying volumes (10, 20, and 30 ml) with concentrations of 10^8 cells per ml to find the optimal dosage for maximum strength. We conducted compressive strength, split tensile strength, and flexural strength tests on the concrete samples at 7 days, 14 days, and 28 days. The results indicated that PPC-based bacteria (30 ml) significantly activated the concrete, leading to a remarkable 29.7% increase in compressive strength, a 28.2% rise in flexural strength, and a 12.7% boost in split tensile strength compared to conventional concrete. Scanning Electron Microscopy (SEM) analysis confirmed the presence of nanoparticles i.e. calcite precipitates, contributing to densification and strength enhancement.