Investigating non-petroleum-based biodegradable polymers as eco-friendly and sustainable materials in asphalt modification: A review on natural rubbers and natural oils

Bitumen, a vital component in asphalt mixtures for road construction, confronts persistent challenges stemming from traffic loads and temperature fluctuations, leading to issues such as permanent deformation, fatigue, and thermal cracking, ultimately jeopardizing road safety. A promising solution involves enhancing asphalt mixture performance through asphalt binder modifiers, including biopolymer materials. Among these, non-petroleum-based biodegradable polymers, such as natural rubber and natural oil, stand out as viable options in highway engineering. This comprehensive review commences by introducing various biopolymeric materials, delving into their types, sources, and processing methods. Their interaction mechanism with bitumen is also discussed. Subsequently, it summarizes the production of bio-advantaged polymer-modified bitumens and mixtures. The study meticulously analyzes the rheological and chemo-mechanical properties of biopolymer-modified bitumens and underscores their mixture performances. Finally, the economic and environmental sustainability of the biopolymer-based bitumens was also evaluated. Natural rubbers enhance rutting, fatigue, thermal cracking, aging resistance, and moisture resistance in bitumen or mixtures, but do increase viscosity, which reduces workability. Natural oils improve fatigue, thermal cracking, and aging resistance without impacting rutting or moisture susceptibility in bitumen or mixtures. Biopolymer-modified asphalt presents the potential to reduce annual maintenance expenses while promoting sustainable road construction. To satisfy road pavement applications, cup lump rubber and extraction oil can be utilized. To further advance this field, future research should focus on utilizing more advanced biopolymers through innovative optimization and interaction mechanisms with other modifiers (e.g., epoxidation and polymerization) to render asphalt mixtures both economical and environmentally friendly without compromising their performance.