Application of Plastic Waste as a Sustainable Bitumen Mixture – A Review

Plastic trash is one of the world's fastest growing environmental issues, with millions of tons ending up in landfills and natural ecosystems each year. At the same time, the road construction industry is facing escalating costs and sustainability problems as a result of its strong reliance on petroleum-based bitumen. Integrating recycled plastic into asphalt provides a twofold benefit, it reduces waste accumulation while also increasing pavement performance. This review compiles data from 51 papers and 251 experimental records to investigate the impacts of plastic alteration on bitumen properties, with an emphasis on penetration, softening point, and viscosity. Consistent trends suggest that adding plastic stiffens the binder, as evidenced by reduced penetration and increased softening point and viscosity. These enhancements improve rutting resistance, but they may make mixing and handling more difficult. This paper uses machine learning (ML) methodologies such as Random Forest and XGBoost to improve predictive understanding by outperforming linear models in capturing nonlinear relationships between dosage, plastic type, and processing conditions. The review identifies knowledge gaps, such as variability across studies, a lack of standardized test methodologies, and insufficient consideration of long-term environmental and economic repercussions. This study provides a synthesis of experimental findings as well as a data-driven methodology for developing long-lasting, high-performance asphalt binders supplemented with plastic waste.