(123c) Thermorheological Behavior of Model Asphalt

Molecular simulations of asphalts provide a method to understand how the structure and modes of molecular motions contribute to the Asphalt viscoelastic response to applied strain or stress.  Results from equilibrium molecular dynamics simulations of AAA-1 model asphalt using two different models (prior AAA-1 model and new AAA-1 model) have been investigated by calculating storage and loss moduli from stress relaxation modulus G(t) data from molecular simulation. Storage and loss moduli have been exploited to calculate complex modulus and phase angle, which are more typical for civil engineers. All models in different temperature show similar phase angle at very high frequency, with the slope of the lower frequency side of the peak increasing with temperature. The slope of complex modulus with frequency shows an opposite temperature dependence, with a faster rise with frequency at higher temperature.  To have better understanding of rheological behavior of new AAA-1 model asphalt, van Gurp-Palmen plot of complex modulus vs. phase angle has been plotted for this model asphalt which shows deviations from thermorheological simplicity over this temperature range. The prior AAA-1 model system, composed of smaller molecules, shows a quantitatively lower complex modulus.