Towards Sustainable Railway Sub-ballast: Field Trial with Recycled Asphalt Pavement and Plastomeric Polymers

This study investigates the feasibility of using high content Reclaimed Asphalt Pavement (RAP) and plastomeric polymers in bituminous railway sub-ballast, also supporting their inclusion in the Italian Railways technical specifications. Laboratory testing, full-scale trial construction, and in situ performance evaluation were performed. Results from the trial section showed that mixtures with 44% RAP can be effectively produced and laid, achieving mechanical performance equal to or higher than that of conventional mixtures with virgin aggregates. The outcomes confirm the technical viability and environmental advantages of high-RAP sub-ballast mixtures, demonstrating a practical pathway toward more sustainable and resilient railway infrastructure.