Estimating the Dynamic Moduli and Viscosities of Bitumens via Oscillatory Strain-Controlled Molecular Simulations

Abstract

This study uses strain-controlled oscillatory deformations in all-atom Molecular Dynamics (MD) simulations to examine the viscoelastic properties of SARA fractions in bitumen. Frequency sweep tests revealed distinct moduli and viscosity ranges, aligning with experimental observations. Saturates were the softest and thinnest, while Asphaltenes were the stiffest and least thermally susceptible. MD simulations identified five viscoelastic regimes—Elastic, Glassy, Rubbery, Rubbery Flow, and Viscous—and highlighted accelerated dynamics, with faster relaxation times of simulations allowing exploration of equivalent Hertz-long oscillations in experimental tests. Ensuring that characteristic timescales in MD simulations correspond to comparable Deborah numbers is critical for accurately capturing stress-related phenomena—an insight that represents a previously unrecognized necessity in MD studies involving bitumens.