Crack sealing evaluation of self-healing mortar with Sporosarcina pasteurii: Influence of bacterial concentration and air-entraining agent

摘要

Microbial induced calcium carbonate precipitation has been recognized as a novel pathway to repair concrete cracks. This study aimed to explore the application of Sporosarcina pasteurii in self-healing mortar preparation, and further investigate the influence of bacterial concentration and air-entraining agent content on crack sealing performance. X-ray diffraction and scanning electron microscope tests were carried out to identify the calcium carbonate in vaterite phase for biomineralization precipitations of S. pasteurii which was utilized for self-healing mortar beam specimens production. Subjected to 3-point-bending test, a V-shape crack was induced from the beam bottom with 0.4 mm width which can be automatically healed due to bacteria metabolic activity. Four different S. pasteurii concentrations, i.e., 0, 2 x 105, 2 x 106 and 2 x 107 cells/ml, were comparatively studied with respect to self-healing mortar property. In general, the higher bacterial concentration corresponded to faster crack healing and 2 x 106 cells/ml was deemed as the proper bacterial concentration. Afterwards, self-healing mortar with various air-entraining agent contents (0%, 0.005%, 0.01%, 0.015% and 0.02% of cementitious material) was also discussed, implying that best flexural strength regain is achieved at 0.01% air-entraining agent. Finally, the crack filling crystals were examined to find bacterial imprints leaving on the surface of calcium carbonate.