Concrete is the most widely used construction material, yet its durability is limited by crack formation. As a promising and environmentally friendly repair solution, biogenic self-healing based on microbially induced biomineralization of calcium carbonate (CaCO3) has been gaining attention. Polyextremotolerant fungi, due to their resistance to alkaline conditions and ability to form extensive mycelium, represent particularly interesting candidates for such applications. The aim of this thesis was to evaluate the potential of 36 selected polyextremotolerant fungal strains for use in concrete repair. We examined their ability to survive in alkaline conditions characteristic of concrete and characterized their capacity for CaCO3 biomineralization. To assess strain properties, we conducted screening tests of alkalotolerance on cement-based media (pH 9-13). Biomineralization via urease activity was promoted on media containing inorganic (calcium nitrate) and organic (calcium lactate) calcium sources. The resulting crystals were analyzed using optical microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and Raman spectroscopy. Our results showed that 30 out of 36 strains tolerated pH 10, and 14 out of 27 strains successfully grew on cement-coated medium supplemented with diatomaceous earth (pH 9-10). Most tested strains produced calcium carbonate minerals in biomineralization media, predominantly calcite, and in some cases vaterite. Four strains also formed calcium oxalates. SEM analysis confirmed a high diversity of crystal morphologies among strains and revealed that fungal hyphae in some strains served as nucleation sites for crystallization. When applied to cement prisms, fungi grew within cracks, although significant mineral filling did not occur. Nevertheless, the results indicate that the selected fungi have great biomineralization potential, but further research is needed for their effective use in concrete.
|
