Performance and Carbon Impact of High-RAP Asphalt Mixtures with Rejuvenators under Hot Climate Conditions: A Critical Review and Proposed Evaluation Framework for Riyadh
Abstract
High reclaimed asphalt pavement (RAP) mixtures are becoming more appealing due to their ability to reduce the need of virgin aggregate and binder, enhance circularity, and have the ability to reduce greenhouse-gas emissions when appropriately designed. However, high-RAP asphalt mixtures are still very responsive to RAP variability, the stiffness of aged-binder, rejuvenator chemistry, and the severity of the climatic environment in the target area. Such interactions are particularly significant in hot-arid landscapes like Riyadh, where high pavement temperatures enhance permanent deformation and aging, as well as in aggressive economic decarbonization objectives that put strain on a need to switch to resource-efficient materials. This paper is purposely designed to be a review-and-framework paper, not an original experimental paper. It integrates published recommendations and representative current research on high-RAP mixtures, rejuvenators, balanced mix design (BMD), warm-mix asphalt and life-cycle assessment (LCA) and converts them into a hot-climate analysis platform that can be used in Riyadh and similar Gulf metropolitan areas. In the review, a pattern emerges in the literature: high RAP tends to increase rutting resistance, whereas cracking resistance and durability become the limiting risks; rejuvenators can partially restore cracking tolerance, but the effect is highly dependent on the type of rejuvenator, dosage, binder content, and RAP source; and carbon reductions ar e technically significant only when the chosen mixture also maintains service life. Reported literature suggests that there are 45-70% RAP with various rejuvenators that may attain satisfactory cracking and rutting
performance with a BMD approach, with dedicated sustainability investigations showing significant decreases in global warming potential and cost compared to control mixtures. Resting on these results, the paper suggests a staged performance-carbon decision model on hot-climate implementation comprising of mixture screening, integrated mechanical testing and realistic LCA boundaries. The manuscript is composed in such a way that it will serve as submission-ready review article and a basis of a future Riyadh-specific experimental study.
Keywords: reclaimed asphalt pavement; RAP; rejuvenators; hot climate; Riyadh; balanced mix design; asphalt sustainability; life-cycle assessment; carbon footprint; warm-mix asphalt
Prepared by the researcher:
Ahmed Abdulnaeem Ahmed Al-Sharman
Independent Civil Engineer (Roads), Riyadh, Saudi Arabia