Effect of SARA fractions on the physical, structural and dynamic properties of bitumen using molecular dynamics simulation

The utilization of molecular dynamics simulation on bituminous materials usually adopts three classical bitumen models (AAA-1, AAK-1, AAM-1). However, the chemical compositions of bitumen, namely SARA fractions, vary significantly in reality, depending on the source of bitumen. In this regard, this study investigated the influence of SARA fractions on the simulated properties of bitumen. To this end, 21 bitumen models with different SARA fractions collected from the literature were established. The radial distribution function (RDF), density, and self-diffusion coefficient (SDC) were derived to characterize the structural, physical, and dynamic properties, respectively. Results indicated that the SARA fractions would not significantly influence the density and radial distribution function of bitumen models. However, the influence of heavy components on the equilibrium of dynamic sampling was pronounced. In the MSD analysis, the temperature variation contributed little to the self-diffusion capability of bitumen when the asphaltene index was close to one. The correlation between SDC and asphaltene index varied depending on the value of the asphaltene index. Specifically, the correlation was positive when the asphaltene index was larger than one, and negative when it was smaller than one.