Coarse grained modeling of nanostructure and asphaltene aggregation in asphalt binder using dissipative particle dynamics

This study aims to develop coarse grained models of asphalt binders and study nanostructure and aggregation behavior of asphalt binders using Dissipative Particle Dynamics (DPD). The coarse-grained models of asphalt binders with different SARA (asphaltene, aromatic, resin and saturate) fractions were built with the mapping of bead groups and the calculation of forcefield parameters. The simulation results were validated through the calculated molecular structure parameters including interlayer distance and diffusion coefficient of asphaltene. The ordered stacking structures (T shape, face-face, and offset face-face stacking) were observed and the aggregation patterns of asphaltene was more obvious between the same type of asphaltene molecules due to selfsimilarity. The aggregation rates of asphaltene of three asphalt binders were found positively correlated with the mass fractions of asphaltene, which can be used to better predict relative viscosity of asphalt binders. The colloid structure of coarse-grained asphalt binders was observed on the mesoscale platform with small variations of localized nanostructure in three asphalt models. On the other hand, asphaltene showed the lowest diffusion coefficient that was similar among different asphalt binders. The analysis findings indicated that coarse grained modeling with DPD enables large-size model asphalt systems for observation of morphology and aggregation of asphaltene, providing foundation to study complex molecular interaction in polymer modified asphalt binder.