Molecular dynamics study on influence of Nano-ZnO/SBS on physical properties and molecular structure of asphalt binder

The purpose of this study is to investigate the influence of nano-ZnO and SBS (styrene-butadienestyrene, SBS) modifiers on the physical properties and structure of asphalt using molecular dynamics(MD) method. In this study, the asphalt molecular model, nano-ZnO molecular model with different particle sizes, SBS molecular model and nano-ZnO/SBS/asphalt blends system were built in Materials Studio (MS) software. Then, the influence of nano-ZnO on the miscibility between SBS and asphalt, and the influence of SBS on the diffusion coefficient of nan-ZnO in asphalt system were researched through MD simulations. The influence of nano-ZnO/SBS on the physical modulus and the molecular structure of asphalt was studied. The results show that nano-ZnO particles decrease solubility parameter of asphalt and improve the miscibility between SBS and asphalt. However, the diffusion coefficient of nano-ZnO in asphalt blends decreases compare to that of blends with SBS. Moreover, nano-ZnO/SBS has a significant positive effect on the bulk modulus, shear modulus, and elastic modulus of the asphalt, especially the bulk modulus. It indicates that the nano-ZnO/SBS will improve the high-temperature and the shear resistance performance of asphalt. Also, nano-ZnO/SBS may alleviate the accumulation of strong polar components and reinforce the tractility of the branched chains in asphalt molecular, which resulting in the tightness of the asphalt molecular structure. All these changes in asphalt molecules contribute to a more stable colloidal structure and better physical properties of asphalt.