A Review of Asphalt Recycling Technologies and the Role of Engineered Bitumen for Sustainable Road Maintenance in Nigeria

Asphalt recycling has emerged globally as a costeffective and sustainable method for road maintenance. Reclaimed Asphalt Pavement (RAP) is the most recycled material in the world, yet its adoption in Africa and Nigeria remains limited. This review synthesizes international practices in asphalt recycling (Copeland, 2016; FHWA, 1995), highlights African experiences (SANRAL, 2014; NCW, 2018), and examines rejuvenator technologies with particular focus on Waste Cooking Oil (WCO) (Al-Sabaeei et al., 2018; Ismail & Al-Hdabi, 2019). A conceptual framework is introduced—the ―Double Waste to Wealth Asphalt Initiative‖—which combines RAP with WCO to produce engineered bitumen with 100% local content. The review emphasizes the importance of incorporating Asphaltene-Maltene (A/M) ratio and Maltene Distribution Ratio (MDR) into Nigeria’s bitumen testing protocols for both virgin and aged binders (Airey, 2000), thereby improving quality control and performance assessment. The paper concludes with policy recommendations for Nigeria to scale up asphalt recycling as a mainstream road maintenance method, ensuring value-for-money, sustainability, and alignment with national infrastructure goals