MODIFICATIONS OF INTERNAL MOLECULAR STRUCTURES OF ASPHALT COMPONENTS DUE TO PHYSICAL AGING

The internal structure of a molecule can be presented in terms of intra-molecular (i.e., inter atomic) and inter-molecular energies such as van der Waals, bond and bending, torsion, and inversion energy. In this study, changes in molecular energies of individual asphalt components are evaluated as a function of physical aging factors. The factors for physical aging such as temperature and pressure are considered in a molecular dynamics simulation framework. The simulations are carried out by varying temperatures within the range from -35oC to 75oC and pressures within the range from 0.95 atm to 1.1 atm. The outputs of the simulations give a clear idea about the internal structure of molecules in liquid state. Simulation results show that physical aging process causes increase in bond stretching, angle bending, and torsion energy. Application of high temperatures results in high stretching of asphalt atoms. At high temperature intermolecular van der Waals repulsion increases. Pressure variation has negligible effects on intra and inter-molecular energy changes. From inversion energy values, the geometry of the molecules is found.