Efficacy of Bacillus Cereus Bacteria in Improving Concrete Properties through Bio-precipitation

Bio-precipitation is a metabolic by-product of specific microbial species. It is a common occurrence that results in the formation of many biological minerals. For example, bio-precipitation occurs when Ca 2+ ions combine with either CO 3 2− or HCO 3− ions. This bio-precipitation process involves several urease-producing bacteria, particularly those of the “ Bacillus ” genus, effectively improving the structural concrete property. This research aims to enhance concrete microstructure by incorporating “ Bacillus cereus ” suspension. Bacterial suspension completely replaced water to prepare 100 mm cubical concrete samples. Ø100 × 200 mm cylindrical specimens were also prepared for the non-destructive analysis. Furthermore, scanning electron microscopy imaging was used to identify differences in the hardened cement paste constituents of both control and bacterial concrete. Prepared samples were obtained from the curing medium and tested for mechanical strength regularly. Using bacterial suspension in concrete resulted in significant improvements in the property, such as the strength and microstructure of this construction material. For the compressive and split tensile strength tests, corresponding maximum increments of 16.9% and 11.8% were noted after 180 days. Following a 180 days curing period, a 4.7% increase in pulse velocity and a 60.2% decrease in water absorption capacity values were also recorded. An empirical equation was also developed to predict concrete strength based on its ultrasonic pulse velocity and water absorption capacity. In microscopic analysis, the incorporation of B . cereus shows the formation of calcite crystals which eventually improve the physical properties of the concrete. Overall, the bacterial inclusion in the concrete improved the mechanical properties and the microstructural performance by ameliorating composite integrity and reducing water absorption capacity.