Temperature and Moisture Impacts on Asphalt before and after Oxidative Aging Using Molecular Dynamics Simulations

Abstract

© 2017 American Society of Civil Engineers. Temperature and moisture impacts on unoxidized and oxidized asphalts' thermodynamic and rheological properties were studied using molecular dynamics (MD) simulations. Changes in asphalt property under different degrees of oxidation, temperature, and moisture content were investigated regarding density, isothermal compressibility, bulk modulus, and zero-shear viscosity. MD simulation results show that the density of asphalt before and after oxidation decreases at a similar rate with an increase in temperature. Bulk modulus (inverse of isothermal compressibility) of asphalt before and after oxidation also decreases with an increase in temperature but with different trends. Because of oxidative hardening, oxidized asphalt shows lower isothermal compressibility, but higher bulk modulus and zero-shear viscosity compared with unoxidized asphalt. When moisture is added, such trends become opposite. Specifically, the zero-shear viscosity of the oxidized asphalt becomes lower than that of the unoxidized asphalt above 5% moisture inclusion. This is true in the case of the density of asphalt with moisture as well, but this finding is not significant.