Optimum concentration of Bacillus megaterium for strengthening structural concrete

•Bacillus megaterium was introduced in concrete to obtain optimum concentration of bacteria.•Microbial calcite precipitation was quantified using conventional techniques.•Higher strength of structural concrete was obtained.

Five different cell concentrations of Bacillus megaterium (10 × 105 to 50 × 105 cfu/ml) were introduced in structural concrete to achieve the optimum concentration of bacteria. The significant increase in the strength was obtained in the case of 30 × 105 cfu/ml at different ages. The strength of highest grade of bacterial concrete had improved (24%) as compared to lowest grade (12.8%) due to calcification mechanism. Microbial calcite precipitation was quantified using X-ray diffraction analysis, visualized by scanning electron microscopy and analyzed by energy dispersive spectrometer. It was found that the optimum concentration of B. megaterium had a positive effect on high strength structural concrete.