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Pollack Periodica
Authors: Vlasta Harbul’áková, Alena Luptáková, Nadežda Števulová, and Pavlína Rutarová

Biocorrosion of natural and synthetic materials is an irreversible biochemical process, where a significant participation of bacteria societies takes place. The biocorrosion of concrete sewer pipes is caused mainly by the sulphuric bacteria and sulphate-reducing bacteria (SRB) forming a part of the biological circulation of sulphur and its compounds in biosphere. The aim of this work was to simulate a biocorrosion and to study the effect of simultaneous action of Acidithiobacillus thiooxidans ( A.t. ) and sulfate-reducing bacteria on concrete samples under model conditions. The biocorrosion effect has been proved and a further study is planed.

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Pollack Periodica
Authors: Vlasta Harbuľáková, Adriana Eštoková, Alena Luptáková, Nadežda Števulová, and Gabriel Janák

Biodeterioration can be seen as a process, which decreases value of materials and constructions and has been defined as the deterioration of materials of economic importance by organisms. Since the discovery bacterial genus Acidithiobacillus caused rapid corrosion of concrete especially Acidithiobacillus thiooxidans .This paper presents the results of concrete specimens’ biodeterioration study by bacteria Acidithiobacillus thiooxidans and Desulfovibrio genera under model conditions. Biodeterioration was carried out in laboratory reactor, where simultaneous effect of Acidithiobacillus thiooxidans and Desulfovibrio genera happened. The pH values of leachate, mass of concrete specimens change, Ca and Fe content in leachate were evaluated. After experiment the morphology of corroded surface were observed by scanning electron microscopy.

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Leaching of calcium ions increases the porosity of cement-based materials, consequently resulting in a negative effect on durability since it provides an entry for aggressive harmful ions, causing corrosion of concrete. Sulphuric acid corrosion of concrete can be caused due to attack of aggressive media naturally existing in the environment. Another possibility of corrosion formation is biogenic acid effect through the agency of microorganisms.

The paper is focused on the investigation of the influence of biogenic acid attack on the cement composites affected with bacteria Acidithiobacillus thiooxidans. The concrete specimens with 95% wt. addition of antimicrobial activated granulated blast furnace slag as durability increasing factor as well as without any addition were studied. The experiments proceeded during the nine 7-day cycles. The pH values and chemical composition of leachates were measured and evaluated after each cycle. The higher resistance of concrete samples with the addition of 95% wt. of antimicrobial activated granulated blast furnace slag to the aggressive environment was confirmed. The leaching of calcium ions of concrete sample affected with bacteria Acidithiobacillus thiooxidans was 1.13 times lower (736.6 mg/L of leachate) for concrete sample with antimicrobial activated granulated blast furnace slag addition comparing to concrete sample of ordinary CEM I Portland cement without any additives (832.0 mg/L of leachate).

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