Effect of Microbial Calcite Precipitation on the Performance of Concrete Incorporating Different Bacterial Strains

Concrete is the unavoidable material of modern construction, but it remains susceptible to cracking, which reduces the strength and durability of the material over time. The need for sustainable alternatives is underlined by traditional repair methods that are often temporary and costly. The integration of bacteria in cementitious systems represents a bio-based approach, in which microbial-induced calcite precipitation (MICP) not only increases strength but also includes self-healing ability. In this study, three strains of bacteria, Bacillus subtilis (BS), Sporosarcina pasteurii (SP), and Bacillus sphaericus (BSp), were directly added to concrete to investigate the effect of these strains on the mechanical and durability properties of the concrete. The findings demonstrated that all bacterial concretes outperformed the control group. At 28 days, the compressive strength was maximum for BSp-1 at 39.62 MPa, followed by BS-2 at 38.36 MPa and SP-2 at 38.20 MPa. Microstructural study confirmed that the presence of calcite filling of pores and cracks leads to denser and more durable concrete. Among all three variants, the blended mix BSp-1 exhibited superior strength, microstructure, and durability. This study concluded that the addition of bacteria enhanced the strength, permeability, durability, and microstructural properties of the concrete.