Study on Microbial Modification of Concrete Cracks in Seawater Environment

In order to improve the repairing effect under seawater,test of using pozzolan as carrier to enhance MICP technology on concrete cracks was carried out.The macroscopic physical and mechanical test and microscopic detection of the restoration were combined to systematically analyze the influence and mechanism of pozzolan on MICP technology repairing concrete cracks.The results show as following:(1) The adaptability of sporosarcina pasteurii domesticated by seawater was obviously enhanced,and the cement production increased significantly.(2) The addition of pozzolan could significantly improve the repairing effect of MICP on concrete cracks.The shear strength of reinforced samples increased by 75.12%~94.94%,while the compressive strength increased by 50.36%.Meanwhile,the permeability coefficient decreased from 10^-2cm/s to 10^-7cm/s,and the acoustic time value decreased by 48.52%~49.16%.(3) The enhancement mechanism of pozzolan on MICP repairing concrete cracks mainly includes three aspects:First,bacteria could be protected by the pozzolan,which contained active oxides that could react with strong base to consume OH^- and reduce the pH value in the fractures.In the meantime,the porous structure of pozzolan can increase the “colonization area” of bacteria and provide a suitable growth environment.Second,the pozzolan itself as a filler optimizes the crack space structure and increases its compactness.Third,the hydration and polymerization reactions of pozzolans generated carbonate-aluminosilicate and other composite gels,which further improved the repairing effect of concrete cracks.