Reuse of waste tennis strings as recycled polymer fibers in asphalt concrete

The reuse of end-of-life polymer-based products as secondary raw materials is an effective strategy to reduce waste and promote more sustainable material systems. In this study, waste tennis strings were investigated as recycled polymer fibers for asphalt concrete, in order to assess their suitability as a reinforcing phase in a composite paving material. An experimental program was conducted to evaluate the effect of the recycled fibers on the mechanical and performance-related properties of asphalt concrete. Stiffness, fatigue resistance, and fracture behavior were examined to determine the influence of fiber addition on the response of the material. The results showed that waste tennis-string fibers can beneficially modify the mechanical behavior of asphalt concrete, with particularly significant improvements in fracture-related performance and a generally positive effect on selected properties. These findings indicate that waste tennis strings can be successfully valorized as reinforcing fibers in asphalt concrete, offering a technically viable recycling route for a post-consumer polymeric waste. More broadly, the study demonstrates the potential of unconventional recycled fibers to enhance the performance of engineering composite materials while contributing to more sustainable resource use.