Recycling aged crumb rubber-modified asphalt pavements: A review

This study provides a comprehensive review of current progress and challenges in recycling crumb rubber-modified asphalt (CRMA) pavements. It examines key aspects, including mechanical performance, rejuvenation methods, chemical characterization, practical case studies, and environmental implications. Particular emphasis is given to the technical barriers that influence recyclability, such as the mix design for recycled mix, accounting for the combined aging of both the asphalt binder and the crumb rubber particles, and optimizing the rubber content alongside chemical interaction of rejuvenating agents. Existing research indicates that several traditional recycling practices, especially full-depth reclamation and hot central plant recycling, are generally suitable for CRMA and can achieve satisfactory structural and functional performance. In contrast, cold and hot in-place recycling methods require further investigation to resolve compatibility constraints and operational limitations unique to rubberized materials. The review highlights that aging alters the physicochemical properties of both the bitumen matrix and the rubber phase, thereby constraining reuse efficiency when standard recycling methods are used. Nonetheless, emerging compound rejuvenation approaches that integrate softening agents with supplemental rubber show potential to restore binder elasticity and improve long-term durability. Environmental and economic assessments consistently demonstrate that recycling CRMA supports resource conservation and aligns with circular-economy objectives. The findings underscore the need to adapt existing recycling technologies and expand targeted research to enhance the sustainable reuse of CRMA in future pavement engineering.