Biomineralization process of CaCO3 precipitation induced by Bacillus mucilaginous and its potential application in microbial self-healing concrete

Microbial induced calcium carbonate precipitation (MICP) is widely common in nature, which belongs to biomineralization, and has been explored carefully in recent decades. The research studied the main factors including temperature, initial pH value and Ca 2+ concentration on bacterial growth and carbonic anhydrase activity by a kind of bacteria producing extracellular carbonic anhydrase, and revealed the biomineralization process of MICP by Ca 2+ concentration and calcification rate in alkali environment. Meanwhile, microbial healing agent containing spores and calcium nitrate was prepared for the early age concrete cracks. The self-healing efficiency was assessed by crack closure rate and water permeability repair rate. After 28 d healing time of dry-wet cycles, compared with reference, the crack closure rate with the crack width up to 0.339 mm could reach 95.62%, the water permeability repair rate was 87.54%. XRD analysis showed that the precipitations at the crack mouth were calcite CaCO 3 . Meanwhile, the self-healing mechanism of mortar cracks was discussed in detail. In particular, there is no other pollution in the whole mineralization process, and the self-healing system is environmentally friendly, which provides a novel idea and method for the application of microbial self-healing concrete.