EFFECT OF CARBONATION ON MICROBIAL CORROSION OF CONCRETES

Carbonation process involves the reduction of surface pH of concrete and is the prerequisite to microbial corrosion to occur. The highest carbonation rate was found in specimens exposed to 0.5% CO2 gas, followed by 5% and control (0.03%) specimens. The carbonation rates for 5%, 0.5%, and control were 7.1, 16.4, and 4.3mm/year, respectively. Microbial corrosion experiment showed that 0.5 % specimens had the highest corrosion rates and percentage mass loss of 3.8mm/year and 13.9 percent/year, respectively. It can be concluded that carbonation stimulated microbial corrosion process. However, under quite high CO2 gas concentration (5%), corrosion process was reduced due to formation of much calcite in the carbonated zone. Growth of T. thiooxidans was stimulated on the reduced pH of carbonated surface.