Title: Remediation of Concrete Using Microorganisms

Author(s): Santhosh K. Ramachandran, V. Ramakrishnan, and Sookie S. Bang

Publication: Materials Journal

Volume: 98

Issue: 1

Appears on pages(s): 3-9

Keywords: calcite; compressive strength; cracking; stiffness

DOI: 10.14359/10154

Date: 1/1/2001

Abstract:
This paper describes an innovative biotechnology utilizing microbiologically-induced mineral precipitation for concrete remediation. Calcite precipitation induced by Bacillus pasteurii was studied in two types of portland cement mortar specimens: one prepared from mixing with microorganisms, and the other with simulated cracks filled with microbial mixtures. The study showed that there was a significant increase in compressive strength of the portland cement mortar cubes containing lower concentrations of live cells. Compressive 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 filled with bacteria and sand demonstrated a significant increase in compressive strength and stiffness values when compared with those without cells. Scanning electron micrographs identified that microbiological calcite precipitation occurred mainly close to the surface areas of the crack, where a dense growth of calcite crystals embedded with cells was observed.