Construction of molecular models of modified waste cooking oil rejuvenated bitumen and nanoscale analysis of thermodynamic and structural properties

Constructing more realistic molecular models can help reveal the nanoscale driving mechanisms of rejuvenators for the recovery of aged bitumen properties. In this study, based on various physicochemical characterization results, including changes in chemical interaction, four-component, and elemental contents before and after aging of bitumen, as well as identification of essential compounds in modified waste cooking oil (MWCO), the molecular models of virgin bitumen, aged bitumen, MWCO and rejuvenated bitumen with different MWCO dosages were developed by using a programming solver. A molecular dynamics approach was used to predict the thermodynamic and structural properties of various bitumen systems and to elucidate the molecular mechanisms of the regenerative effect of MWCO on aged bitumen. The molecular simulation results indicated that the predicted density ρ , glass transition temperature Tg, cohesive energy density (CED), solubility parameter δ , and radial distribution function (RDF) agreed with the actual measurement results and published literature. In other words, the molecular models constructed in this study possess properties similar to those of asphalt materials, and the proposed simulation method is feasible. The rejuvenation process reduced ρ , CED, δ , RDF curve peak, non-bonding energy, and van der Waals energy of the aged bitumen and increased its free volume fraction and diffusion coefficient. It demonstrated that MWCO attenuated the intermolecular interactions of aged bitumen and increased the migration and activity space of the molecules, resulting in improved workability, uniformity, and relaxation properties. This study adds insights into MWCO rejuvenated bitumen at the nanoscale.