A Critical Review of Recycled Plastic Waste Integration in Asphalt Pavements: Advancing Sustainable Infrastructure Development in Africa

This comprehensive review systematically examines the integration of recycled plastic waste (RPW) as a sustainable modifier in asphalt pavements, presenting a transformative approach to addressing Africa's dual challenges of infrastructure deficit and plastic pollution. Through rigorous meta-analysis of 187 peer-reviewed studies and 23 implementation case studies from 2010-2024, we establish that optimized RPW incorporation, particularly utilizing polyethylene (PE) and polypropylene (PP) polymers at 4-8% loading by bitumen weight induces fundamental microstructural and rheological transformations in asphalt binders. Advanced characterization reveals the formation of three-dimensional polymer networks that enhance complex modulus by 40-80% while reducing phase angles by 10-20o, translating to 40-70% improvement in rutting resistance and 15-30% enhancement in moisture damage resistance. Our analysis demonstrates that RPW-modified asphalt achieves performance grade elevation of 1-2 levels, significantly extending pavement service life by 30-50% in tropical African conditions. The review identifies critical implementation barriers including heterogeneous waste streams, limited technical capacity, and inadequate policy frameworks, while proposing a comprehensive adoption strategy encompassing standardized specifications, economic incentives, and capacity building programs. Environmental life cycle assessment confirms 20-25% reduction in carbon footprint and substantial landfill diversion benefits. This work establishes RPW-modified asphalt as a technically superior, economically viable, and environmentally responsible solution that aligns with circular economy principles, offering African nations a pathway to simultaneously enhance infrastructure resilience, reduce environmental pollution, and create green economic opportunities through localized value chains and community engagement models. Keywords: Recycled Plastic Waste (RPW), Polymer-Modified Asphalt, Sustainable Pavements, Circular Economy, African Infrastructure.