Understanding relationships between aging induced variation of asphaltene aggregation morphology and asphalt properties through molecular dynamics simulation

The distribution characteristic of asphaltene molecules in asphalt stays being debated, especially under the effect of asphalt aging. This work took visualization benefit of the molecular dynamics (MD) simulation into observing aging induced morphological variation of asphaltene aggregation and analyzing its relationship with asphalt property changes. The asphaltene aggregation of asphalt under different aging degrees was characterized by X-ray diffraction tests and self-diffusion examinations. Then, visualization analyses were conducted to depict the morphological variation of asphaltene aggregation induced by asphalt aging. Under external loadings, the evolution of asphalt mechanical responses and asphaltene aggregates deformation were investigated. Finally, the diffusion process of rejuvenators into asphalt influenced by asphaltene aggregation was analyzed. The results show that, asphaltene molecules construct three-dimensional network structures with clusters linked by scattered molecules. This results in the restricted self-diffusion model of asphalt. The effort of asphalt aging is gathering scattered molecules together to expand the cluster size without causing regular arrangements. This strengthens the resistance against external loadings but weakens the deformation ability of asphalt. Moreover, the further compressed space around asphaltene clusters retards the diffusion activity of both maltenes and rejuvenators. The findings provide evidences for microstructural model of asphalt and suggest the confinement sizes of asphalt self-diffusion for quantitatively estimating asphalt aging degrees and evaluating rejuvenation efficacies.