R+D to Watch: Bacteria to Repair Concrete

Today's laboratory research can become tomorrow's building product. This is part of a continuing series of posts about technologies with exciting potential.

Repairing and extending the durability of concrete structures is a multi-billion dollar industry, Researchers at Ghent University have proposed the use of microbes to repair cracks in concrete:
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.
FORECAST: Watch for biological processes such as this coming to a bridge near you before the end of the decade.