Modifications of Internal Molecular Structures of Asphalt Components Due to Physical Aging

Abstract

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