Research on the formation mechanism of bee-like structures in asphalt binders based on molecular simulations

To investigate the effect of the chemical composition of asphalt binders on its bee-like structure, aimed at three common direct distillation asphalt, considering the distribution characteristics of alkane with long chain, sulfide, condensed aromatics, and asphaltenes compounds, molecular dynamics simulation and test study of the formation mechanism of the microcosmic phase state of asphalt binders were carried out. Combining assembled asphalt molecular models using known representative components, the effectiveness of models was verified in element asphalt component, the distribution of four components, average molecular weight, and the micro morphology by atomic force microscope (AFM). The images of potential field of atom volume and surface characteristic from molecular models, as well as the trajectory charts of molecular dynamic were used to investigate the contribution of different molecules to the microcosmic phase state of asphalt binders. The results show that asphaltenes are one of the reasons for the white district formation in relatively high height of bee-like structure. Alkane with long chain can insert into the layers of asphaltene molecules or the gap of large curling asphaltene molecules which form subsidence area in honeycomb. However, sulfide and condensed aromatics with high polar and small steric hindrance can attach to the aromatic segments of asphaltene and lead to a subsidence areas with high value of adhesive force but low value of elastic modulus.