Preparation Of Binary Microbial Self-healing Agent And Application In Concrete Crack Healing

As we all know,concrete cracks provide a convenient channel for the rapid invasion of harmful ions,which seriously affects the durability and service life of concrete.Therefore,the crack repair of concrete has always been a hot issue of the industry.In recent years,microbial self-healing method has attracted much attention due to its great healing potential and environment-friendly nature.In this paper,aiming at the problems existing in the current research of microbial self-healing,such as the shallow repair depth,the unclear quantitative relationship between microbial concentration and substrate dosage,the research on crack self-healing of concrete with bacteria is carried out,the main contents and research results are as follows:Bacillus pasteurii was selected as the bacterium A(BA),the mineralization yield of BA under different substrate concentration and different bacterial concentration was respectively studied,the precipitate was analyzed by XRD and SEM,and the concentration of substrate was determined,the quantitative relationship between bacterial concentration and substrate was defined,so as to develop the microbial selfhealing agent A,then the self-healing effect of cracks with different bacteria concentration was studied through the area self-healing rate and the impermeability ratio.The results show that the higher the substrate concentration is,the better the mineralization yield will be;The relationship between the amount of bacteria and substrate is linear;The higher the bacterial concentration,the better the self-healing effect.The wider the concrete crack,the more remarkable the difference in healing effect of bacteria with different concentrations;In addition,the healing effect of the crack immersed in deep water is better than that of the shallow position.Saccharomyces cerevisiae was selected as bacterium B(BB),then a binary microbial self-healing agent is obtained by combining BA and BB.The slef-healing effect of crack with the two bacteria was verified through comparing the healing of crack surface and the distribution of mineralized products at different depths.The results show that the healing depth of crack increased after the combination of BA and BB.In order to further improve the self-healing effect,the binary microbial self-healing agent was optimized.The alkali resistance test and acclimation of BA and BB were carried out respectively,then the best combination method and proportion of the BA and BB were studied.The results show that the alkali resistance of BA is up to 13,while the highest alkali resistance of BB is 11.5;When the ratio of BA:BB = 6:4,The influence of growth and reproduction among each other is the least,and the mineralization yield is the most.The optimized binary microbial self-healing agent is used to prepare the selfhealing concrete,the effect of crack healing was characterized by the area healing rate and the deposition depth of calcium carbonate.Meanwhile,the workability and setting time of the self-healing concrete were measured to study the influence of the selfhealing agent.The results show that the optimized binary microbial self-healing agent can improve the self-healing depth of crack and ensure the healing width;The binary microbial self-healing agent can improve the fluidity of concrete,but it will cause retarding.