Multiscale mechanical quantification of self-healing concrete incorporating non-ureolytic bacteria-based healing agent

This paper investigated non-ureolytic bacterially-induced precipitation of calcium carbonate as a self-healing strategy for concrete cracking. By incorporating bacteria and calcium source nutrients as a two-component healing agent in concrete matrix, the process of bacterially mediated calcium carbonate deposition was trigged upon crack formation and self-sealing of cracks can be expected. The effectiveness of healing was evaluated by mechanical tests in macroscale (flexural and ultrasonic pulse velocity) and nanoscale (nanoindentation), respectively. Both the repair method and the type of calcium source have a significant impact on the healing efficiency. The healing ratio and recovery ratios of flexural strength and modulus of the two-component self-healing with calcium glutamate were higher than that of control series by a factor of 2. A transition zone, whose average nanomechanical values were approximately 20% higher than that of outer precipitates, acted as a strong bond between the matrix and deposited layer from calcium glutamate.