Determination of the degree of microbiological damage to the «Cement Concrete - Steel Reinforcement» system

The degree of corrosion damage by microorganisms to the concrete wall of the basement is investigated. The biofilm on the surface of the concrete wall under study is formed by micromycetes Aspergillus niger, bacteria Bacillus subtilis, Actinomycetes, nitrifying bacteria Nitrosomonas, lactic acid bacteria Lactobacillus and sulfate-reducing bacteria Desulfovibrio. The waste products of microorganisms consist of organic acids secreted by micromycetes of Aspergillus niger, ammonium ions, carbonate-, nitrate-, sulfide-ions secreted by bacteria. To establish the corrosion state of steel reinforcement in biodegradable concrete, the electrode potential was measured. The established values of the surface potential of steel reinforcement are in the range -351 ÷ -376 mV. This suggests that the probability of local corrosion of steel reinforcement in a biodegradable concrete wall is strong. It will take about 20 years to achieve an aggressive concentration of organic acids at the surface of steel reinforcement in biodegradable concrete with a layer thickness of 5 cm. However, in conditions of constant moistening of the concrete surface, this period is reduced to 10-11 years. The predicted rate of local corrosion of steel reinforcement in concrete exposed to microorganisms is at least 0.2 mm/year. It was found that the depth of concrete destruction under the influence of microorganisms, mainly micromycetes Aspergillus niger, for 20 years is 1.3 cm; for 50 years is 2.1 cm.