Method for Evaluating Compatibility between SBS Modifier and Asphalt Matrix Using Molecular Dynamics Models

To further evaluate the compatibility between asphalt matrix and styrene-butadiene-styrene (SBS) modifier using a molecular dynamics (MD) method, MD models of asphalt matrix, SBS modifier, and SBS-modified asphalt were first established. Solubility parameters and interaction energy were utilized to discuss the compatibility between asphalt matrix and SBS modifier. The simulated results indicate that asphalt is compatible with SBS modifier, and the compatibility at 160 degrees C is much better than that at 120 degrees C. The interaction between SBS modifier and asphalt matrix increases their compatibility, and the van der Waals potential energy predominates in the intermolecular potential energy, playing an important role in forming a stable blending system of SBS-modified asphalt. Further, interactions among asphalt components and SBS modifier cannot inhibit the molecular diffusion of each component, lowering the compatibility between asphalt and SBS modifier at 120 degrees C. However, the higher temperature at 160 degrees C inhibits SBS diffusion and increases the interaction and compatibility between SBS and asphalt. This study reveals the segregation mechanism of SBS-modified asphalt.