Integrating Recycled Plastics into 100% Reclaimed Asphalt Pavement for Enhanced Asphalt Mixtures

Abstract: Reclaimed asphalt pavement (RAP) is one of the most commonly recycled materials in asphalt pavement construction. Its use not only reduces the need for landfill space but also offers a sustainable solution for reusing asphalt materials. However, state agencies have limited the use of RAP due to concerns about its performance when used in higher amounts. At the same time, plastic waste presents significant environmental and waste management challenges when disposed of in landfills. A promising solution to address both issues is to incorporate recycled plastic into RAP for asphalt pavement construction.

This study investigated the use of three types of recycled plastics—recycled polypropylene (rPP), recycled high-density polyethylene (rHDPE), and recycled low-density polyethylene (rLDPE)—at dosages of 0.3%, 0.6%, and 0.8% in 100% RAP, combined with the warm mix asphalt additive Evotherm P25. Laboratory tests, including the indirect tensile cracking test (IDEAL CT), ideal shear rutting test (IDEAL RT), Cantabro loss test, and moisture damage test, were conducted to assess the performance of the modified asphalt mixtures. Additionally, a mechanistic-empirical analysis using PerRoad software was performed to evaluate long-term performance.

Laboratory test results showed that incorporating recycled plastics improved the cracking tolerance index but reduced workability, particularly with rHDPE, which required more gyrations for proper compaction. rLDPE enhanced volumetric properties due to its melting behavior during mixing but resulted in increased mass loss, compromising durability. rHDPE also improved the mixture’s rutting resistance, although higher plastic dosages reduced overall rutting tolerance. The PerRoad analysis indicated a fatigue life of less than two years for the pavement design considered in this study. Statistical analysis revealed that both dosage and plastic type significantly influenced the performance of asphalt mixtures in terms of cracking and rutting resistance, with plastic type being particularly significant in the Cantabro loss test. Overall, this research highlights the potential of integrating waste plastics into 100% RAP for asphalt pavement.