Preliminary study on repairing tabia cracks by using microbially induced carbonate precipitation

Abstract

Cracks are a type of damage often present in earthen sites, which have a particular influence on the structural performance. Cracks constitute preferential paths for rainfall infiltration, directly moistening the rammed earth and substantially reducing its mechanical properties. Therefore, the repair of cracks is an important part of the protection and reinforcement of earthen sites. Calcium carbonate is one of the main components of the tabia. The use of microbially induced carbonate precipitation (MICP) to repair and protect the tabia is not only environmentally friendly but also compatible with the substrate. In this paper, a crack-repair method dominated by MICP is proposed to repair the cracks of the tabia, and the repair effect is evaluated by experimental methods. First, the influencing factor test of MICP and the reinforced soil column test were carried out to determine the suitable parameters for repairing cracks, including the concentrations of bacteria and cementation reagent, filled soil particles and the number of grouting cycles. Then, the pre-damaged tabia samples were repaired using the suitable parameters, and the repair effect was verified. The results showed that when the crack width is 5 mm, the average flexural strength and shear strength recovery ratios of the specimens after MICP repair were 79.92% and 88.54%, respectively, showing a very satisfactory repairing ability. However, the recovery ratio tends to decrease as the crack width increases. In addition, the static contact angle test results showed that the MICP not only repaired the crack but also enhanced the hydrophobicity of the crack. MICP technology can be used as an effective method to repair cracks in the tabia.