Green Recycling and Long-Term Immobilization of Disposable Medical Masks for Enhanced Mechanical Performance of Self-Compacting Recycled Concrete

The global outbreak and prolonged presence of Coronavirus Disease 2019 (COVID-19) have resulted in a substantial accumulation of discarded masks, posing serious environmental challenges. This study proposes an eco-friendly and low-carbon strategy to repurpose discarded DMFM fibers as a key component in fiber-reinforced self-compacting recycled aggregate concrete (FRSCRAC). The mechanical and environmental performance of FRSCRAC was systematically evaluated by investigating the effects of recycled coarse aggregate (RCA) replacement ratios (0%, 50%, 100%), discarded DMFM fiber material (DMFM) contents (0%, 0.1%, 0.2%, 0.3%), and fiber lengths (2 cm, 3 cm, 4 cm) on axial compression failure mode and stress–strain behavior. The results demonstrated that DMFM fibers significantly enhanced concrete ductility and peak stress via the fiber-bridging effect. Based on fiber influence, modified stress–strain and shrinkage models for SCRAC were established. To further understand the fiber fixation mechanism, X-ray computed tomography (X-CT) and scanning electron microscopy (SEM) analyses were conducted. The findings revealed a stable random distribution of fibers and strong interfacial bonding between fibers. These improvements contributed to enhanced mechanical performance and the effective immobilization of polypropylene microfibers, preventing further microplastics release into the air. This innovative approach provides a sustainable solution for recycling and effectively immobilizing discarded DMFM fibers in concrete over long curing periods, while also enhancing its properties.