Strengthening of bacterial concrete with metakaolin as a partial replacement for cement – A Case Study

Abstract

Concrete is a common construction material used for constructing buildings for various functions. Concrete undergoes an increase in strength, accompanied by the formation of shrinkage cracks during curing. Shrinkage fissures function as a conduit through which reactive fluids can infiltrate the inner structure of the concrete. Under optimal conditions, the fluids cause a decrease in the pH of the core, resulting in the corrosion of the reinforcing bars. In this work, Bacillus licheniformis MTCC 3353 is employed to produce calcite and effectively seal small fissures. The investigation also encompassed a partial substitution of cement with metakaolin (10 – 15% of the mass of cement). The utilization of bio-based concrete specimens resulted in enhancements in both mechanical strength and durability parameters. The bacterial specimens increased the strength by 20 - 22% in compression and flexure testing compared to the conventional concrete. The bacterial specimens had higher durability since the pores were filled with secondary cementitious material due to a reaction with calcium hydroxide. A microstructural analysis was employed to verify the occurrence of calcite precipitation. The identification of calcite inside the concrete structure is demonstrated by the utilization of FESEM and XRD analyses. An investigation of the growth of bacteria when superplasticizers were added was also done. The growth of bacteria was not affected by the presence of chemicals in concrete, therefore indicating the feasibility of manufacturing high-performance concrete (HPC).