Durability enhancement and prevention of damage in reinforced concrete structures using bacteria

Abstract

Microbial induced calcium carbonate precipitation (MICP) has a potential to improve the durability properties and remediation of cracks in concrete. In this study, bacterial admixed treatment and bacterial spray treatment of concrete structures with ureolytic bacteria was carried out using different media components (especially nutrient media, urea and calcium source). In the first stage of investigation, influence on the addition of bacterial culture and organic components (carbon and nitrogen content) of bacterial growth media on the setting characteristics of cement, chemical and structural properties of microbial concrete was studied. In this study, main emphasis was placed upon replacing the commercially available laboratory grade nutrient broth (NB) with corn steep liquor (CSL), which is an industrial by-product. Addition of plain NB media without bacteria severely retarded the setting of cement paste as well as significant reduction in the compressive strength was observed in concrete specimens. In fact, the addition of plain CSL media without bacteria had no adverse effect on the setting characteristics of cement paste and strength properties of concrete. While, setting characteristics of cement paste remain unaffected on the addition of bacterial culture grown in NB/CSL media. In bacterial treated concrete, MICP as a result on the addition of bacterial culture grown in NB/CSL media significantly improved the compressive strength and permeation properties. Bacterial admixed treatment (that can be used for new structures) and bacterial spray treatment (that can be used as a repair procedure) were found to be effective in MICP treatment of concrete. In the comparative analysis of CSL and NB as a nutrient media, CSL would serve as a potential alternative nutrient source for bacterial cells in microbial treatment of concrete. Further, durability of microbial treated concrete under aggressive environments was explored.