Mechanical, microstructural, and free-vibration characteristics of concrete reinforced with recycled E-waste PVC fibers.

This study investigates the influence of recycled polyvinyl chloride fibers derived from electronic waste on the mechanical and free-vibration characteristics of concrete. Fibers of two lengths (30 mm and 50 mm) were incorporated at contents of 0.8%, 1.0%, and 1.2%, and their effects on compressive strength, flexural strength, and free-vibration response were evaluated. Scanning electron microscopy was employed to examine fiber-matrix interactions and associated energy dissipation mechanisms. Results indicate that a fiber content of 0.8% yields the highest compressive strength, while higher contents result in slight reductions, which may be attributed to fiber agglomeration and increased porosity. In contrast, flexural strength increases progressively with fiber content, reaching a maximum of 22.1% at 1.2%, with longer fibers (50 mm) providing additional enhancement due to improved crack-bridging capacity. Free-vibration testing reveals a maximum increase in the damping ratio of approximately 7.47%, primarily governed by fiber content, with fiber length exerting a comparatively minor influence. Microstructural observations reveal strong interfacial bonding accompanied by localized debonding and controlled fiber pull-out, which likely contribute to enhanced energy dissipation. These findings suggest that recycled polyvinyl chloride fibers can serve as a sustainable reinforcement strategy for improving the free-vibration performance of concrete.