Compatibility between twin-screw desulphurized crumb rubber and asphalt binder based on molecular dynamics simulation

The widespread application of crumb rubber modified asphalt is limited by its inadequate storage stability, which is largely governed by the compatibility between the asphalt binder and crumb rubber. This study investigated the influence of desulphurized crumb rubber with different solubility on the compatibility and storage stability of modified asphalt by combining molecular simulations with experimental validation. The results demonstrate that the compatibility between desulphurized crumb rubber and asphalt is strongly dependent on solubility when the difference in solubility parameter exceeds approximately 1.5 (J·cm⁻³)^1/2. Desulphurized crumb rubber with a solubility of approximately 28.66 exhibited the highest interfacial binding energy, reduced phase separation, and improved storage stability, whereas excessive desulphurization decreased interfacial binding energy and increased the tendency for phase separation.

Molecular dynamics (MD) simulations and density functional theory (DFT) calculations were performed using Materials Studio 2023. MD simulations were carried out with the Forcite module using the COMPASS III force field. Following geometry optimization and annealing, the systems were equilibrated under the NPT and NVT ensembles, and the solubility parameter, interaction energy, mean square displacement, and fractional free volume were calculated. DFT calculations were performed using the DMol³ module with the BLYP functional within the generalized gradient approximation (GGA) to investigate the intermolecular interactions. Desulphurized crumb rubber with different solubility was prepared by a twin-screw extrusion process, and the simulation results were validated using the separation softening point difference and multi-stress creep recovery (MSCR) tests.