Application of bio-remediation with bacillus megaterium for crack repair at low temperature

Less calcium carbonate in low temperature significantly restricts the application of microbial-induced carbonate precipitation (MICP) technology. Bacillus megaterium was chosen and calcification precipitation tests were studied via varying experimental conditions. Moreover, crack repair tests based on MICP were performed, using the viable cell concentration, sonic time values, unconfined compressive strength and productive rates for calcium carbonate as indicators to evaluate repair effects. Results show that adding nutrients to the gelling solution and determining the optimal reaction conditions can increase production rates for calcium carbonate in low temperature. However, for undomesticated and domesticated B. megaterium, the optimum calcification reaction conditions were different. With MICP technology, cracks were successfully sealed by calcium carbonate in low temperature and the strengths of specimens with different crack widths all recovered. The smaller the crack width, the better was the microbial utilization efficiency but worse repair uniformity. The repair effect with undomesticated B. megaterium was worst, and the specimens repaired by the method, domesticated B. megaterium and adding urea, had the best repair effect. Therefore, results demonstrated the feasibility of MICP crack repair at low temperature, which lay the foundation for subsequent practical engineering application with B. megaterium in low temperature.