Enhancing compatibility of crumb rubber in modified asphalt using green desulfurization for sustainable waste tire recycling

The practical application of crumb rubber (CR) modified asphalt is significantly constrained by phase separation phenomena arising from poor matrix compatibility. This study proposes an innovative deep eutectic solvent (DES)-assisted desulfurization strategy to enhance CR-asphalt interfacial compatibility, thereby advancing sustainable pavement materials and valorizing waste tire resources. Through controlled DES treatment, desulfurized crumb rubber (DCR) was synthesized with tailored molecular architecture. Comprehensive characterization through crosslink density analysis, Horikx plots interpretation, functional groups, and micro-structure coupled with energy-dispersive spectroscopy revealed two fundamental modification mechanisms: (1) selective cleavage of 51 % crosslinks in the rubber network, and (2) successful grafting of amide functionalities onto the DCR surface. These synergistic effects endowed DCR modified asphalt with exceptional performance characteristics, demonstrating 31 % enhanced ductility and 61 % improved storage stability (separation index reduction from 5.6°C to 2.2°C). The reduced crosslink density facilitates polymer chain mobility for better asphalt interpenetration, while the introduced amide groups establish strong interfacial interactions with acidic asphalt components through hydrogen bonding and covalent coupling. This dual-approach modification strategy provides a scalable pathway for developing high-performance modified asphalt with superior compatibility.