Eco-Friendly Highways: Harnessing Waste Polystyrene and Reclaimed Asphalt Pavement for Sustainable Roadways and Environmental Mitigation

This study presents an innovative approach to addressing environmental concerns associated with waste expanded polystyrene (WEP) and reclaimed asphalt pavement (RAP). In this research, WEP was utilized as a bitumen modifier, while RAP was employed as a substitute for virgin aggregates. Specifically, 4% shredded WEP, relative to the bitumen weight, was directly integrated into the bitumen during the melting process. Various proportions of RAP material (0%, 20%, 40%, and 60% relative to aggregate weight) were used as replacements for virgin aggregates. The incorporation of WEP enhanced the resistance of the modified bitumen (MB) to permanent deformations and high temperatures compared to conventional bitumen. Simultaneously, the inclusion of RAP significantly improved the performance of asphalt mixtures. The combination of 4% WEP and 40% RAP facilitated a robust bond between aggregates and asphalt paste, resulting in a remarkable 20.73% increase in stability, 8.62% increase in indirect tensile strength, 17.81% reduction in permanent deformations, 32.19% improvement in rut depth resistance, and 36.2% increase in resilient modulus. Moreover, moisture resistance also saw a 6.3% improvement. It's worth noting that exceeding a 40% RAP content negatively impacted the performance of asphalt mixes. Substantial cost savings of up to 32% and 25% were achieved by replacing virgin aggregates with 60% and 40% RAP, respectively, in the wearing course of Hot Mix Asphalt (HMA). Ultimately, implementing 4% WEP as a bitumen enhancer and replacing 40% of virgin aggregates with RAP materials not only enhances pavement performance but also reduces waste and conserves natural resources, contributing to broader societal efforts to mitigate environmental impacts.