The influence of repair technique on the distribution of biogenic CaCO₃ in a mimic vertical crack

Microbially induced carbonate precipitation (MICP) is a promising solution for the remediation of concrete cracks. It has great advantages of environmental compatibility and exceptional penetration of cracks owing to its low-viscosity solution. Despite of these, practical application of MICP has been hindered by challenges including limited efficiency of in situ microbial deposition of CaCO₃, extended repair cycles, and suboptimal strength recovery. Addressing these issues, this study undertook a comprehensive exploration of key repair process parameters for repairing cracks within the simulated crack space through inducing CaCO₃ precipitation by a urease producing bacteria, specifically, the flow rate of the repair agents (7.958, 15.91, and 39.79 μL/min), the pre-sealing length of the crack (one-third of the crack length, half of the crack length, and full sealing), and the injection port position (upper, middle, and bottom of the crack). Their impacts on the distribution of bio-CaCO₃ and overall repair effectiveness were examined in detail. Optimal repair performance was achieved at a flow rate of 15.91 μL/min, with full crack sealing, and the injection port situated at the bottom. This configuration resulted in a remarkable coverage rate of crack side wall, crack surface repair rate, and crack volume filling rates of 94.38%, 79.48%, and 100% respectively, and the first two were calculated using Image J software. The crack repair depth was significantly improved. Relative contribution rates to repair effectiveness was found to be ranked as follows: injection port position > flow rate > pre-sealing length. This study provides critical insights into the optimization of MICP repair process parameters, presenting a significant advancement in the understanding and development of effective techniques for concrete crack repair.