Repair of concrete existing micro-cracks by use of microbially induced carbonate precipitation

Department of Civil Engineering, School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xianning West Road 28, 710049 Xi’an, China

^* Corresponding author: jianyun.wang@xjtu.edu.cn

Abstract

Micro-crack is the start of concrete deterioration and failure, though it does not decrease the bearing capacity in the beginning. In order to prolong the service life of existing concrete structures, it is important to repair the existing micro-cracks before they develop into large cracks, which are much more harmful. Bio-genic CaCO₃ from microbially induced carbonate precipitation (MICP) process is proved to be a promising crack repair material due to its environmental friendliness and super compatibility with cementitious matrix. In this study, MICP based repair technology was applied to repair micro-cracks. The influence of crack environment and repair technique on the precipitation of bio-CaCO₃ was investigated. Results shown that moderate alkali pH had limited effect on the properties of bio-CaCO₃. Bacteria could still induce the CaCO₃ precipitation in crack if it was saturated with Ca²⁺ containing deposition medium. Crack of a width 0.5mm can be fully sealed within 3 days by use of a controlled injection technique.