微生物矿化沉积碳酸钙技术修复混凝土既有微裂缝研究进

Concrete is the most widely used construction material because of its easy-cast,low price and high compressive strength. However,due to its intrinsic heterogeneity and non-ideal working environment,concrete could not tolerate too much tension forces and hence is prone to crack during service,which is the start of concrete deterioration (such as water seepage) and concrete failure. In order to prolong the service life of existing concrete structures,global researchers have acquired positive progress in recent years in exploratively utilizing a new technology to repair micro-cracks in existing concrete,i. e. microbial-induced carbonate precipitation (MICP) technology. This technology is environmentally friendly and compatible with concrete matrix. The repairing agents used are of low viscosity and hence easy to penetrate into the deep part of the crack, which can result in a homogeneous healing inside crack space. The repairing efficiency is closely related to the bio-CaCO₃ deposition mechanism and repair procedure. This review intends to summarize the research progress of MICP technology in the repair of existing concrete micro-cracks from the aspects of microbial-induced calcium carbonate deposition mechanism and repair procedure,both of which are of great significance in that applicative research topic. The biogenic CaCO₃ precipitation based on bacterial urease catalyzed urea hydrolysis is one of the mostly studied processes owing to its high CaCO₃ production and ease of control. But that process has an unignorable flaw-generation of ammonia as a by-product. So we suggest in the paper the combinational use of two or three mineralization mechanisms maybe a solution for that problem. With respect to the repair procedure, either a one-step or a two-step procedure can be used for MICP-based crack repair and the addition of healing components can be realized by the methods of immersion, spraying and injection. Among the three methods,the injection is most applicable in practice,and the use of a retention aid or a moisturizing agent can help to prolong the retention of the repairing agents inside cracks and consequently to obtain effective CaCO₃ precipitation. This paper is expected to provide a prospect and reference for further promoting the practical application of MICP technology in the repair of existing micro-cracks in concrete under service.