Phase-field modeling of fracture and healing in BioFiber-Reinforced Concrete

Self-healing concrete has been extensively studied for its potential to reduce maintenance and reconstruction costs, with various strategies developed to embed healing functionality. As an alternative to vascular networks, which may compromise mechanical performance due to stress concentrations around internal channels, BioFiber Reinforced Concrete (BioFRC) introduces a damage-responsive and self-activated healing mechanism through embedded bioengineered fibers. Given the structural complexity of these fibers, a detailed numerical simulation is necessary to evaluate their fracture and healing behavior. In this study, the phase-field method is employed to simulate the damage-healing response of BioFRC, where each fiber comprises a PVA core, a middle coating layer (endospore-laden hydrogel sheath), and an outer polymeric shell that protects the inner components, a system that has not been thoroughly examined before. A parametric study is conducted across ten models with varying fiber permutations to assess the influence of hydrogel material behavior (i.e., quasi-brittle when dry and viscous when wet), fiber geometrical features, healing time (associated healing ratio), and the mechanical properties of the microbially induced calcium carbonate precipitation (MICCP), which is the healing end-product. Results show that the transition to a viscous hydrogel significantly reduces fracture resistance, while longer fibers with thinner coatings enhance energy absorption and peak force. Additionally, both healing duration (e.g., one-week vs. four-week healing) and MICCP stiffness critically affect recovery performance. These findings provide quantitative insights into the mechanical performance of BioFRCs. They also inform manufacturing strategies aimed at optimizing design by leveraging both the peak load capacity prior to fracture and the recovery behavior following fiber breakage and healing.