Advancing Sustainable Asphalt Binders: Hybrid Modification with Crumb Rubber and Recycled High Density Polyethylene for Enhanced Performance and Ageing Resistance

This study develops a sustainable asphalt binder through a hybrid modification using crumb rubber (CR) and recycled high-density polyethylene (RHDPE), incorporating sulfur and polyethylene-grafted maleic anhydride as compatibilisers. Experimental assessments included frequency sweep tests, multiple stress creep recovery (MSCR), and linear amplitude sweep (LAS) analyses, examining viscoelastic behaviour, high-temperature rutting resistance, and intermediate-temperature fatigue performance, respectively. Low-temperature cracking resistance was evaluated using stress ratio tests, while binder durability was assessed through pressure ageing vessel (PAV) and ultraviolet (UV) exposure. Results revealed significant improvements in high-temperature rutting resistance and fatigue life at moderate strains for hybrid CR/RHDPE-modified binders, comparable to commercial SBS-modified binders, alongside reduced sensitivity to UV and PAV ageing. Increased CR content promoted the formation of a robust elastic polymer network, whereas higher RHDPE content enhanced structural reinforcement without compromising storage stability or workability at up to 6% content. Hybrid CR/RHDPE-modified binders exhibited greater and more complex sensitivity to ageing, showing pronounced alterations and ongoing interactions within their polymeric networks during ageing, thus warranting further investigation into these mechanisms. Although low-temperature cracking resistance remained somewhat inferior to SBS-modified binders, hybrid binders demonstrated superior ageing resistance. Notably, CR/RHDPE-modified binders maintained substantial stiffness even after extensive fatigue damage, demonstrating their potential for constructing resilient, sustainable pavements with reduced maintenance requirements.