Multiscale investigation of service performance and intrinsic mechanisms of vulcanized Eucommia ulmoides gum modified asphalt

In this study, vulcanized Eucommia ulmoides gum modified asphalt (VEUGMA) was prepared using natural plant-based Eucommia ulmoides gum (EUG) as the matrix. Its service performance was first evaluated, followed by a mechanistic exploration via analyses of chemical functional group indices, elemental composition, microscopic morphology, and mechanical properties. Molecular models of VEUGMA with different degrees of crosslinking (DCL) were constructed to determine the optimal DCL range, alongside correlation analyses among the macroscopic rutting factor (G*/sinδ), microscopic DMT modulus, and nanoscopic Young's modulus (E). The results revealed that the crosslinking network in VEUGMA significantly improved the asphalt's high temperature deformation resistance and endowed it with excellent elastic recovery, temperature stability, and storage stability. Among tested formulations, the 3.5/6VEUGMA blend exhibited the most outstanding performance. VEUGMA is characterized as a high performance modified asphalt dominated by chemical modification with auxiliary physical effects: C[dbnd]C groups in EUG react with vulcanizing agents to form thioether bonds and crosslinking networks, while concurrent asphalt reactions—including naphthene dehydroaromatization and aromatic ring alkylation—consume saturated hydrocarbon groups (CH₃, CH₂) and =C-H bonds, leading to the generation of new C[dbnd]C double bonds. These reactions restructure the asphalt's chemical composition and molecular network, forming an EUG-skeleton-based crosslinking framework. Validation of the molecular models indicated that a DCL of 40 −60 % provides an optimal balance between crosslinking density and asphalt performance. Strong correlations were observed between the macroscopic G*/sinδ and microscopic DMT modulus, as well as between the microscopic DMT modulus and nanoscopic E, confirming that cross-scale analysis is an effective method to reveal the service performance mechanisms of asphalt materials.