Microorganisms versus stony materials: a love-hate

Micro-organisms can have a devastating effect on building materials. They produce a range of organic and inorganic acids and enzymes, inducing solution and alteration of mineral phases. Biofilms alter the water exchange of the material and also mechanical effects add to the biodeterioration. One especially deleterious process in which bacteria are involved, is biogenic sulphuric acid corrosion in sewer systems. On the other hand, some types of bacteria can be used in engineering applications, for example for biological cleaning and bioconsolidation. Bacterially induced carbonate precipitation has been proposed as an environmentally friendly method to consolidate and protect decayed limestone or cementitious materials. The method relies on the bacterially induced formation of a compatible and highly coherent carbonate precip- itate. Furthermore, the same principle can be applied for manual or autonomous remediation of cracks in concrete and the bacteria are in this case used as self healing agents.