Application of encapsulated expanded vermiculites as carriers of microorganisms and nutrients in self-repairing concrete

Self-healing concrete based on microbial mineralization has become a promising technology to enhance the durability of concrete structures in the past decade. However, the development of carriers that can immobilize microorganisms and load nutrients without any negative effects has become a limitation. In this research, vermiculite has served as carriers for bacteria and nutrients. The immobilizing capacity, protective effect, repairing performance and mechanical compatibility of this carrier have been studied, and also the mechanism of this system has been also explored. The results indicated that expanded vermiculite was a suitable microbial carriers considering its huge water absorption capacity and electrostatic adsorption of bacteria, and the wrapped outer protective layer of low-alkali sulphoaluminate cement was important for the improvement in water resistance. Cracks with width below 0.5 mm were almost completely healed after 28 days of incubation and the repairing products observed by SEM were irregularly shaped and tightly packed calcium carbonate crystals. In addition to accelerating self-healing, loading microbial self-healing agents with wrapped vermiculite had excellent compatibility with concrete.