THE INFLUENCE OF MICROORGANISMS ON THE PHYSICAL AND MECHANICAL PROPERTIES OF CONCRETE

The article considers the change in the physical and mechanical characteristics of cement stone made of the CEM I 42,5 N Portland cement in the process of bacterial and fungal corrosion for 6 months in the air and moisture conditions. It is established that the density of concrete during microbiological corrosion increases under constant moistening of the sample. However, after drying, a decrease in the density of concrete is recorded by 10 % under the influence of Bacillus subtilis bacteria and by 14 % under the influence of black mold. The degree of influence of microorganisms on the amount of water absorption of cement stone is established experimentally. Bacteria increases water absorption by 7 %, black mold increases water absorption by 10 %. Within 6 months, water absorption increased from 21 to 24,5 % for bacterial corrosion in indoor conditions, and from 24 to 29 % for fungal corrosion. When exposed to capillary moisture for 6 months, the water absorption of concrete increased to 30,4 % under the influence of Bacillus subtilis bacteria and to 37,3% under the influence of Aspergillus niger van Tieghem fungi. An increase in the water absorption of concrete is associated with an increase in porosity due to biodegradation. Under room conditions of exposure to bacteria, the porosity increases from 14,1 to 15,3 %, and from 14,3 to 17,9 % after exposure to black mold. With constant moistening, the porosity of cement concrete increases to 19,1 and 25,6 % with bacterial and fungal corrosion, respectively. The loss of compressive strength of cement stone is 13 % under the influence of bacteria and 15 % under the influence of fungi in the air for 6 months. In case of microbiological corrosion of concrete under conditions of constant wetting, the strength decreases by about 35 % in 6 months

Forecasting the durability of reinforced concrete under conditions of microbiological corrosion

The article presents data on the study of the kinetics of liquid corrosion of cement concrete infected with microorganisms Bacillus subtilis and Aspergillus niger. The equilibrium concentrations of calcium cations during fungal and bacterial corrosion of cement concrete in an aqueous medium are established. According to the profiles of calcium hydroxide concentrations in the thickness of cement concrete during fungal and bacterial corrosion, it was found that during fungal corrosion of concrete, the intensity of interaction of calcium hydroxide with the products of the vital activity of microorganisms is higher than during bacterial corrosion. In case of fungal corrosion under conditions of Aspergillus niger infection, citric acid has the greatest impact on concrete since its amount in the products of the vital activity of microorganisms is maximum. Profiles of concentrations of aggressive substances by the thickness of the concrete sample show that bacterial corrosion proceeds more slowly than fungal corrosion and allow us to calculate the time to reach the maximum concentration of aggressive substances at the surface of steel reinforcement in concrete. Corrosion of reinforcement in concrete with fungal corrosion will begin in 2.5 years after infection, with bacterial corrosion after 5.5 years.

Determination of lacquer contained in samples of cultural relics by enzyme-linked immunosorbent assay

As an environmentally friendly natural polymer material, lacquer is durable, anti-bacterial, corrosion-resistant and decorative.