Remediation of concrete using micro-organisms

This paper describes an innovative biotechnology utilizing microbiologicall y-induced mineral precipitation for concrete remediation. Calcite precipita tion induced by Bacillus pasteurii was studied in two types of portland cem ent mortar specimens: one prepared from mixing with micro-organisms, and th e other with simulated cracks piled with microbial mixtures. The study show ed that there was a significant increase in compressive strength of the por tland cement mortar cubes containing lower concentrations of live cells. Co mpressive strengths of the cubes containing live or dead cell mass, however decreased as cell concentrations and curing time increased, suggesting the interference of mortar integrity by biomass. Cracks piled with bacteria an d sand demonstrated a significant increase in compressive strength and stif fness values when compared with those without cells. Scanning electron micr ographs identified that microbiological calcite precipitation occurred main ly close to the surface areas of the crack, where a dense growth of calcite crystals embedded with cells' was observed.