Fungi-enabled high-performance healing of wide cracks in mortar under nutrient-stimulated conditions

This study develops an innovative and efficient fungi-based self-healing concrete technology capable of repairing wide cracks under nutrient-stimulated conditions. Calcium alginate encapsulation method was utilized to incorporate fungi-based healing agents into mortar mixtures. Fungal capsules were added at concentrations of 2%, 3.5%, and 5% by weight of cement and compared with control groups without capsules. Results showed that mixture with 2% and 3.5% fungal capsules maintained appropriate workability, while mixtures with 5% capsules exhibited reduced flowability. After curing, mortar specimens were artificially cracked to create narrow, medium, and wide cracks. In the small crack group, both control and fungi-containing samples showed complete crack closure within 10 days. Fourier Transform Infrared (FTIR) analysis revealed that self-healing in control samples was due to autogenous healing mechanisms, while fungi samples exhibited additional healing through fungi-mediated pathways, evidenced by the presence of oxalate chemical bonds. In contrast to the control group, where medium and wide cracks largely unhealed, samples containing fungal capsules demonstrated significantly enhanced healing. Medium cracks with width of 0.1–0.4 mm were fully healed after 14 days (D14). For wide cracks, the control group exhibited a healing rate of only 15.8%, while the addition of 2%, 3.5%, and 5% fungal capsules increased the healing rate by 464%, 554%, and 597% of the control samples respectively. These findings highlight the potential of fungi-based self-healing technology as a sustainable and effective approach for enhancing the durability of concrete structures, particularly in healing wide cracks.