This paper presents a comprehensive review of the environmentally friendly management and reutilization of electronic waste (e-waste) plastics in flexible pavement construction. The discussion begins with an overview of e-waste management challenges and outlines key recycling approaches for converting plastic waste into asphalt-compatible materials. This review then discusses the types of e-waste plastics used for asphalt modification, their incorporation methods, and compatibility challenges. Physical and chemical treatment techniques, including the use of free radical initiators, are then explored for improving dispersion and performance. Additionally, in situations where advanced pretreatment methods are not applicable due to cost, safety, or technical constraints, the application of alternative approaches, such as the use of low-cost complementary additives, is discussed as a practical solution to enhance compatibility and performance. Finally, the influence of e-waste plastics on the conventional and rheological properties of asphalt binders, as well as the performance of asphalt mixtures, is also evaluated. Findings indicate that e-waste plastics, when combined with appropriate pretreatment methods and complementary additives, can enhance workability, cold-weather cracking resistance, high-temperature anti-rutting performance, and resistance against moisture-induced damage while also offering environmental and economic benefits. This review highlights the potential of e-waste plastics as sustainable asphalt modifiers and provides insights across the full utilization pathway, from recovery to in-field performance.

This study investigated the feasibility and performance of using soybean oil as a bio-based recycling agent in recycled asphalt pavement (RAP) for road reconstruction in cold regions. A comprehensive demonstration project was conducted on a 5-mile section of Old State Road in Clare County, Michigan, where a 100% RAP mixture modified with soybean oil was produced and placed using a conventional asphalt paver equipped with a screed. Laboratory evaluations included balanced mix design, rutting and cracking testing, and binder performance analysis. Field application processes, including mixing and compaction, were also documented and evaluated. The asphalt mixture tests included the Hamburg wheel-tracking test (HWTT) and the indirect tensile asphalt cracking test (IDEAL-CT), while the asphalt binder tests included dynamic shear rheometer (DSR), asphalt binder cracking device (ABCD), rotational viscometer (RV), linear amplitude sweep (LAS), Fourier transform infrared spectroscopy (FTIR), and CO ₂ emission analysis. An optimal soybean oil dosage of 1.0 wt.% (based on the total weight of the mix) significantly improved low-temperature cracking resistance and fatigue life while maintaining rutting resistance. Results showed that soybean oil improved compaction performance and exhibited a cracking temperature approximately 3.3°C lower than that of untreated RAP based on the ABCD test. Fatigue performance was also enhanced. Fourier transform infrared spectroscopy (FTIR) analysis confirmed the chemical compatibility and interaction between soybean oil and the RAP binder. On-site application was completed smoothly without workability issues, and the final pavement met all compaction and density requirements. In summary, using soybean oil as an RAP recycling agent provides a practical and environmentally friendly solution to improve the performance of recycled asphalt mixes, especially for low-volume roads in cold climates, while supporting the sustainability of Michigan’s pavement and the growth of the soybean market.

The incorporation of crumb rubber derived from waste tires in asphalt pavements has gained increasing attention as a strategy to enhance performance while reducing environmental impacts, particularly in cold regions such as the Midwestern United States, where pavements are subjected to severe thermal stresses and freeze–thaw cycles. Despite the numerous performance benefits observed in previous laboratory-scale studies, field demonstrations can play a critical role in validating the use of recycled waste tires as asphalt additives. This study examines the performance benefits and environmental impacts of incorporating recycled tire rubber into asphalt mixtures via a dry modification process for cold-climate applications. Building on these findings, this paper is based on a full-scale field demonstration of a dry-process rubber-modified asphalt pavement constructed in Ann Arbor, Michigan. Performance testing was conducted at both the binder and mixture levels, and field cores were collected during the construction of field sections. To complement the performance evaluation, a life-cycle assessment (LCA) was conducted to quantify the environmental impacts of rubber-modified asphalt and conventional asphalt. The results indicate that successful rubber incorporation, combined with improved low-, intermediate-, and high-temperature performance, enhances long-term durability compared with control sections. Moreover, despite slightly higher initial environmental impacts associated with rubber incorporation, improved durability and reduced maintenance frequency can lead to lower life-cycle impacts over the long term. The findings highlight the potential of rubber-modified asphalt as a sustainable, resilient solution for cold-region pavements, offering practical insights for agencies seeking to balance performance and environmental impacts in future infrastructure design.