Crumb rubber modified straw oil-based asphalt (CR-SOBA): A multi-scale investigation linking molecular interaction to macroscopic performance

The use of crumb rubber (CR) in straw oil-based asphalt (SOBA) is a promising sustainable strategy, yet its application is limited by an unclear understanding of the modification mechanisms within this unique bio-asphalt system. This study employs a multi-scale approach to establish the preparation-microstructure-performance relationships of CR-modified SOBA (CR-SOBA). Experimental results identified 150 °C as a representative preparation temperature that facilitates optimal rubber swelling while maintaining colloidal stability, providing a consistent baseline for systematic dosage evaluation. This temperature strikes a critical balance between enhanced high-temperature performance and a trade-off in low-temperature ductility. MD simulations provide mechanistic insights into this selection by revealing it as a “kinetic-thermodynamic” sweet spot. Furthermore, the study elucidates that the modification’s success is rooted in the strong molecular compatibility between CR and SOBA, specifically the powerful interaction energies between the CR polymers and the aromatic and resin fractions of the binder. An optimal dosage of 20% CR was determined, and the molecular rationale behind its superior moisture resistance was explored at the molecular level: this formulation exhibited the highest adhesion work retention rate under wet conditions (66.5%). By providing these direct links between processing, molecular interactions, and macroscopic performance, this work offers crucial mechanistic insights that advance the rational design of sustainable, high-performance bio-asphalt binders.