Molecular simulation and experimental analysis of interaction and compatibility between asphalt binder and Styrene-Butadiene-Styrene

• Developed coarse grained models to study interaction between asphalt and SBS with different molecular structures. • Validated model results through asphaltene aggregation and diffusion coefficient. • Conducted complex viscosity tests and microscopy observation of SBS-modified asphalt. • Evaluated compatibility and stability through interaction energy and gyration radius of SBS from simulation. Asphalt binder modified by styrene butadiene styrene (SBS) has been widely used for improving pavement quality. However, compatibility issues between asphalt and SBS remain for phase separation and storage stability. This study aims to investigate the compatibility between asphalt and SBS with different molecular structures. Coarse grained models for asphalt binder were built based on Dissipative Particle Dynamics (DPD) and validated based on the calculated interlayer distance and diffusion coefficient of asphaltenes. The interaction energy and gyration radius were used as performance indicators of compatibility from molecular simulation; while complex viscosity tests and fluorescence microscopy were conducted for experimental evaluation. The results show that asphaltenes would aggregate more in SBS-modified asphalt than in virgin asphalt. The addition of SBS reduces diffusion coefficients of aromatics, resins, and saturates, but not asphaltenes. The SBS with less styrene shows the stronger interaction energy and the larger gyration radius intersecting with asphalt matrix, thus improves compatibility and stability of SBS-modified asphalt. These findings are in good agreements with the viscosity results of Cole–Cole plots and the observed phase morphology of SBS-modified asphalt. The analysis findings provide fundamental understanding of the interaction mechanisms between SBS polymer and asphalt at molecular scale.