Use of bacteria to repair cracks in concrete

Magnel Laboratory for Concrete Research, Ghent University, Department of Structural Engineering, Technologiepark Zwijnaarde 904, B-9052 Ghent, Belgium; Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Coupure Links 653, B-9000 Ghent, Belgium
Cement and Concrete Research (Impact Factor: 3.11). 03/2013; DOI: 10.1016/j.cemconres.2009.08.025

ABSTRACT As synthetic polymers, currently used for concrete repair, may be harmful to the environment, the use of a biological repair technique is investigated in this study. Ureolytic bacteria such as Bacillus sphaericus are able to precipitate CaCO3 in their micro-environment by conversion of urea into ammonium and carbonate. The bacterial degradation of urea locally increases the pH and promotes the microbial deposition of carbonate as calcium carbonate in a calcium rich environment. These precipitated crystals can thus fill the cracks. The crack healing potential of bacteria and traditional repair techniques are compared in this research by means of water permeability tests, ultrasound transmission measurements and visual examination. Thermogravimetric analysis showed that bacteria were able to precipitate CaCO3 crystals inside the cracks. It was seen that pure bacteria cultures were not able to bridge the cracks. However, when bacteria were protected in silica gel, cracks were filled completely.