Sulphur Oxidizing Bacteria as the Causative Factor of Biocorrosion of Concrete

The start and the course of corrosion is conditioned by many factors which include, in addition to the most studied physical and chemical factors, biological effects like influence of vegetation and microorganisms causing the so called biocorrosion. The majority of studies focusing on microbiology of biocorrosion of concrete have indicated that the autotrophic oxidizing bacteria Acidithiobacillus thiooxidans and sulphur reducing bacteria Desulfovibrio genera are the causative microorganisms. This paper aims at study of the biocorrosion degree of concrete samples exposed to the model conditions. Concrete biocorrosion proceeded in a laboratory reactor by sulphur oxidizing bacteria Acidithiobacillus thiooxidans exposure during 80 days at constant temperature of 30 °C. The pH values, Ca and Si ions of concrete samples leachate were measured and evaluated. The pH values were slightly increased. The silicium ions concentrations in leachate increased when compared with the initial concentrations. The formation of gypsum and ettringite was proved by microscopic methods.