Upcycled Waste for Binder Modification: Insights from the United Arab Emirates

Abstract: This study investigates the integration of upcycled polymeric waste into asphalt binders as a sustainable alternative to conventional binders used in the United Arab Emirates (UAE). Currently, the UAE produces around 4.6 million metric tons of hot-mix asphalt (HMA) annually, with 96% relying on neat binders (NB) and 4% on SBS-modified binders (PMB). While PMB addresses durability challenges in the UAE’s hyper-arid climate, it overlooks the opportunity to utilize waste materials like end-of-life tires and plastics. This research introduces two innovative upcycled composites namely the DVR-LDPE and DVR-PP, with the idea of combining the elastic properties of devulcanized rubber (DVR) with the stiffness of polypropylene (PP) and low-density polyethylene (LDPE). By incorporating these upcycled waste into asphalt binders, this study developed a balanced binder system that retains flexibility without compromising high-temperature performance. This composite approach not only mitigated the individual weaknesses of each waste material (DVR and plastics) but also capitalized on their synergistic effects, producing binders with enhanced performance comparable to PMB. The study assessed the influence of incorporating 20% upcycled modifier, by weight of the binder, on the performance of two unmodified base binders sourced from Shell and Richmond. Moreover, to contextualize the efficacy of these innovative composites within standard industry practices, the PMB (PG 82-22) prevalent in UAE asphalt applications, served as a benchmark for evaluating the performance of the upcycled composites modified binders. Linear viscoelastic analysis, high-temperature performance grading, multiple stress creep recovery testing (MSCR), and fatigue resistance evaluation were conducted. The upcycled composites showed similar levels of adaptability to both base binders, suggesting broad applicability in the UAE asphalt industry. This adaptability manifested in significant improvements in the elastic response and stiffness of the binders, which contribute to better high-temperature performance and extended fatigue life, especially evident in the DVR-LDPE modified binders. Black space analysis reveals that unmodified base binders exhibit an asymptotic behavior at higher temperature indicative of a completely viscous response. However, with the addition of the composites, the curves shift toward lower phase angles following the PMB. Such behavior is characteristic of “modifiers”, as they alter the binder’s viscoelastic response by reducing its viscous behavior and increasing the elastic response, aligning upcycled DVR-plastic composites with conventional polymer modifiers like the SBS. The MSCR test classified DVR-LDPE and DVR-PP binders in the "E" category for heavy traffic, comparable to PMB. The Linear Amplitude Sweep (LAS) test evaluated fatigue resistance, with DVR-LDPE binder showing superior performance, significantly outperforming both the DVR-PP and PMB. For the DVR-LDPE binder, the number of loading cycles to failure at 2.5% strain was 2.5 times higher than the PMB. The superior performance of the DVR-LDPE continued even at the higher strain level of 5%. The introduction of upcycled waste composites, especially DVR-LDPE, shows promise for the UAE asphalt industry. Continued investigation into the long-term performance and ecological impacts of these innovative binders will be crucial in moving towards more sustainable infrastructure development in the UAE.