Thermo-physical Properties of Asphalt Predicted using Molecular Dynamics Simulation

Abstract

This study is an essential step to get thermo-physical properties of asphalt using molecular dynamics simulation. It deals with the validity of dreiding force field for asphalt binder model. Both all atom and united atom models of asphalt are considered in my study to find the better model for MD simulation applying dreiding force field potential function. The potential energy values at different time steps are compared to get the appropriate number of time steps for which the system reaches equilibrium. It is found that the cutoff radius exceeding 6 Å does not significantly improve the accuracy. Molecular dynamics method is employed here to compute the density, glass transition temperature, heat of vaporization, and cohesive energy density of asphalt model at different temperatures varying from 218.15 to 358.15 K. With increase in temperature, density, heat of vaporization, and cohesive energy density of asphalt model decrease. From the simulation outputs, density vs. temperature graph is plotted. The graph shows a sharp change in the slope at 258.15 K (–15ºC) which proves the presence of glass transition temperature in asphalt.

Keywords: Asphalt, molecular dynamics simulation, glass transition temperature, heat of vaporization, cohesive energy density