Controllable decrosslinking of waste tire rubber as asphalt substitute: From elastic filler to colloidal rubberized asphalt

The sustainable disposal of waste tire rubber (WTR) for greater effectiveness and efficiency presents a considerable challenge to the petrochemical industry. Currently, the complicate crosslinking networks within WTR and the ambiguous recycling process make the precise management of rubber asphalts extremely difficult. This study presents a controllable decrosslinking strategy, where rational reactive screw extrusion paves the way for transforming WTR into targeted asphalt substitutes. The decrosslinking mechanism and effects are investigated based on the structural changes in both soluble and insoluble components of the tire rubber, and the resulting properties of modified asphalts. The results show that tire rubber with different decrosslinking degree can be controllable produced by adjusting the evolution of crosslinking network. The main networks of rubber components are decrosslinked into sol part, which are compatible with asphalt and characterized by a molecular weight of approximately 10,000 g/mol. Additionally, the core–shell carbon black with micro-nano structures is exfoliated from the secondary networks, which demonstrate fine binding potential. The decrosslinking degree is positively correlated with the processability and low-temperature performance of asphalt, achieving an 88.6 % viscosity reduction and PG 88–28 (25 % substitution, lightly decrosslinked) and PG 76–34 (40 % substitution, deeply decrosslinked). Targeted asphalt binders can be prepared by regulating the degree of decrosslinking and the level of substitution. In-situ morphology observed via Cryo-electron microscopy shows that the incorporation of decrosslinked rubber promotes the formation of a novel colloidal structure within the asphalt. This study introduces a novel and clear solution to achieve the controllable upcycling of waste tires into asphalt substitutes.