A novel electromigration-based microbial self-healing strategy for existing concrete structures

The prevailing self-healing of concrete cracks based on microbial-induced carbonate precipitation (MICP) has been limited to new structures since healing agents have to be pre-embedded during fresh mixing stage. In this study, a novel microbial self-healing strategy based on electromigration of bacterial spores is proposed for existing concrete. To this end, the feasibility of this new method is first verified, and the self-healing performances of the microbial mortar based on electromigration of spores are assessed. Results reveal that the applied electric field improves the physiological activity of spores but not affects the mineralogy and morphology of biomineralized products. Although a prolonged electrical treatment time or an enhanced electric field intensity results in a loss of physiological activity, the number of spores migrated into the mortar increases. The viability of spores is well preserved upon electromigration, and most of the spores are identified in the subsurface layer of the mortar with a thickness over 200 μm. With an electric field intensity of 1 V/cm and treatment time longer than 18 h, the crack width and crack area healing ratios for initial cracks within 600 μm were close to 100 %, and the resistance coefficient to water penetration improves by nearly 4 orders of magnitude. This study successfully extends the application scenarios of microbial self-healing of concrete.