LAUSR

Abstract Phase separation and thermal stability of polymer modified asphalt are the most challenging issues that significantly affect the performance of asphalt in engineering applications. This paper employed phase field method to study phase separation behavior of styrene-butadiene-styrene (SBS) modified asphalt, aiming to reveal the key parameter controlling the phase separation process and evaluate the influences of various styrene-butadiene structures on phase behavior. Combined with the observation from fluorescence microscopy (FM), phase field model related to polymer structure was established for each SBS modified asphalt. The model parameters shed lights on interaction and swelling among SBS and asphalt. Furthermore, the coupled Navier-Stokes equations phase field model (NSPFM) was developed to simulate thermal stability of SBS modified asphalt. The simulated stability was compared with stability observed from experimental test. The results indicated that the block ratio of SBS significantly affects the phase behavior of modified asphalt, which explains the changes of morphology. The diffusion and swelling of SBS molecule as well as the interaction among polystyrene blocks, polybutadiene blocks, and asphalt component mainly control the phase separation process. By comparison with microscopy images, it was proved that NSPFM is an effective approach to track the phase separation process during storage. The simulated stability results were consistent with experimental results of tube tests.