Investigation of Biofouling and Its Effect on the Properties of Basalt Fiber Reinforced Plastic Rebars Exposed to Extremely Cold Climate Conditions

Abstract

For the first time, the possibility of penetration of mold fungi mycelium and spore-forming bacteria into the structure of basalt fiber reinforced plastic rebars has been shown in laboratory and field experiments. Biological contamination at the “fiber-binding” border reveals areas of swelling and penetration of mold fungi mycelium and bacterial spore cells into the binder component. After the exposure of samples at extremely low temperatures, strains of mold fungi of the genus Aspergillus were also isolated from the surface of the rebars. Additionally, spore-forming bacteria of the genus Bacillus immobilized for samples from two years ago. This indicates the high viability of immobilized strains in cold climates. Aboriginal microflora isolated by the enrichment culture technique from the samples was represented by: actinobacteria of the genera Nocardia and Streptomyces; yeast of the genus Rhodotorula; and mold fungi of the genus Penicillium. It was shown that the enrichment culture technique is a highly informative method of diagnosing the bio-infection of polymer composite materials during their operation in extremely low temperatures. The metabolic activity of the cells of cryophilic microorganisms isolated from experimental samples of basalt fiber reinforced plastic rebars was associated with the features of the enzymes and fatty acid composition of the lipid bilayer of cell membranes. In the case of temperature conditions when conventional (mesophilic) microorganisms stop developing vegetative cells, the process of transition of the lipid bilayer of cell membranes into a gel-like state was activated. This transition of the lipid bilayer to a gel-like state allowed the prevention of crystallization and death of the microbial cell when the ambient temperature dropped to negative values and as a result, after thawing, growth resumed and the metabolic activity of the microorganisms was restored. Studies have been carried out on the effect of biodepletion on the elastic strength characteristics, porosity and monolithicity of these materials, while at the same time, after a two year exposure, the strength preservation coefficient was k = 0.82 and the porosity increased by more than two times. The results show that the selected strains affect the properties of polymeric materials in cold climates in relation to the organic components in the structure of polymer composites.