Application of Waste Rubber, Oil, and Rubber-Oil Composite in Asphalt Binder Modification-A Comprehensive Review

Modified asphalt binders are essential for enhancing the performance and durability of pavements. In the pursuit of sustainable road construction, incorporating waste materials, such as scrap automotive rubber and oil-based by-products, into asphalt binders has gained considerable attention. Scrap rubber, a major environmental concern, can improve the binder's resistance to rutting and moisture damage when used in modification. However, challenges remain in enhancing fatigue and cracking resistance, as well as achieving storage stability. Oil modifiers like waste engine oil, cooking oil, vegetable oil, and pyrolytic oils (derived from waste tires, plastics, and biomasses) improve asphalt’s fatigue resistance and low-temperature flexibility. Despite the many advantages of oil-modified asphalt binders, their performance at elevated temperatures remains an area that demands further refinement. Recent advancements focus on hybrid or composite modification strategies that combine rubber and oil to create binders with enhanced performance across a broader temperature range. This approach addresses both high-temperature stability and low-temperature flexibility, offering a more balanced and resilient asphalt pavement solution. The blending method critically influences modifier interaction with asphalt binders, directly impacting material performance and making it essential for optimizing the benefits of composite binder modification. This article highlights how combinations of rubber and oil modifiers hold the potential to revolutionize asphalt technology in the years ahead. The review offers a detailed analysis of the storage stability, chemo-rheological properties, aging resistance of binders, and the influence of blending approaches on the performance of rubber-modified, oil-modified, and composite-modified asphalt binders. The article concludes by outlining significant research gaps and suggesting directions for future studies, emphasizing the crucial role of innovative composite modification methods in enhancing the performance of asphalt binders and supporting sustainable practices in asphalt road construction.