Applications of microbial calcium carbonate precipitation in concrete through denitrification: a review

This study aims to review the potential for microbial calcium carbonate precipitation (MCP) as an effective method for environmental remediation and its application in construction restoration. This review aims to provide in-depth knowledge of microbial calcium carbonate precipitation through the concrete denitrification process. One of the critical parameters reviewed in this study is the choice of denitrifying bacteria that can be used for inclusions in concrete. There are limited reports on denitrifying bacteria used in concrete for enhancing its mechanical and durability characteristics. Hence, this study reviews the different types of denitrifying bacteria that can be used in concrete. Diaphorobacter nitroreducens and Pseudomonas aeruginosa with cell concentration in the range of 10 5 –10 9 CFU/ml along with calcium formate and calcium nitrate as nutrients are found to be effective. For these bacterial inclusions, the crack healing efficiency is found to range from 350 to 590 µm for 28 days depending on the protective carrier used. Another critical parameter reviewed in this study is the suitable technique for microbial inclusions into concrete. To determine the effectiveness of self-healing, the concentration of bacterial cells required and nutrients required are also reviewed. Additionally, the capacity of denitrifying bacteria as an instrument of self-healing against crack formation is evaluated. Finally, the broad applications of microbial calcium carbonate precipitation through denitrification are discussed in various fields, and the drawbacks of application in concrete are discussed. Overall, it is discovered that the denitrification pathway is more environmentally friendly while still being as successful as current techniques in enhancing the mechanical characteristics of concrete.