Towards fungi-mediated self-healing concrete: An interdisciplinary explorative study on the survival and biomineralization of fungal species in cementitious environments

Concrete is the most used construction material worldwide due to its abundant availability, structural characteristics and inherent ease of manufacturing and application. However, the material bears several drawbacks such as the high susceptibility for crack formation, leading to reinforcement corrosion and structural degradation. Extensive research has therefore been performed on the use of microorganisms for biologically mediated self-healing of concrete by means of calcium carbonate (CaCO3) precipitation. Recently, filamentous fungi have been recognized as high-potential microorganisms for this application as their hyphae grow in an interwoven three-dimensional network which serves as nucleation site for CaCO3 precipitation to heal the crack. This potential is corroborated by the current state-of-the-art on fungi-mediated self-healing concrete, which, at the beginning of this PhD research, is not yet extensive but valuable to direct further research. This PhD project therefore aims to expand the limited state-of-the-art by exploring various parameters and conditions in a laboratory environment to tackle knowledge gaps and provide insights to the field. Ultimately, the research covers multiple key aspects for the fungal species Trichoderma reesei and Neurospora crassa. Nutritional sources to sustain the fungal species in a cementitious environment are investigated. The influence of alkalinity and different cement types on fungal growth and survival is assessed. Insights on CaCO3 precipitation are gained, optimal biomineralization conditions are discovered and techniques to visualise and analyse the precipitated crystals are grasped and applied. Protection of the microbial spores from the harsh concrete conditions is addressed by looking into the encapsulation of the fungal spores. Finally, the repertoire of potential candidate species is extended by isolating fungal strains from a concrete-relevant environment and screening these on their ability to grow and biomineralize CaCO3 in a cementitious setting. Thanks to the interdisciplinary nature of this research, combining architectural, biological and chemical perspectives, the foundations of the state-of-the-art are reinforced and new ones are built.