Evaluation of performance of the cracked concrete repairing with microbially induced calcium carbonate precipitation (MICP) technique

This article aims to evaluate the cracked concrete repaired by using the microbially induced calcium carbonate precipitation (MICP) technique with Lysinibacillus sphaericus strains LMG 22257 and EW-S2. The concrete sample used in this study had a compressive strength of about 40 MPa at 28 days, and two types of concrete shapes were prepared, i.e., 1) cube concrete with a dimension of 150x150x150 mm3 which was used to determine the compressive strength, and 2) concrete beam having a dimension of 150x150x600 mm3 and reinforced with 2-RB12 mm steel bar, which was used to evaluate the corrosion of steel reinforcement embedded in concrete and the ability of crack healing. The crack concrete was made in cube samples to have 0.2 mm in width, 20 mm in depth, and 90 mm in length by using a plastic sheet. For reinforced concrete beams, the crack was created by four-point loading until a crack width of 0.2-0.3 mm was obtained. The results found that that the concrete repaired with the MICP technique exhibited higher performance in terms of higher compressive strength and lower steel corrosion compared to the concrete without repairing but slightly lower than the concrete without crack. Moreover, the microstructure analysis of the repaired concrete showed that the main product was calcium carbonate (CaCO3), which was caused by the MICP. These results also suggested that the use of bacteria via the MICP technique could be to use to repair the concrete crack.