An empirical model for modified bituminous binder master curves

Abstract

Modeling the mechanical behavior of asphalt binders and mixtures has been the subject of intensified research in recent decades. Master curves of the norm of the complex modulus |G*| in the linear viscoelastic domain are frequently used for modeling, while phase angle master curves are less frequently considered for this purpose. Therefore in this research, an empirical model is introduced for phase angle master curves of modified and neat bituminous binders. The model is based on a general form of a double-logistic (DL) mathematical function. The |G*| master curve was then modeled using a mutual relationship between the phase angle and |G*|. Master curves of three neat and seven modified binders were generated and used to validate the DL model. The results showed that the model is capable of properly predicting the plateau region of phase angle master curves. In particular, the asymptotic behavior of the master curves at high frequencies can be modeled correctly. The model also describes irregularities in the high temperature range of the phase angle master curve. In general, model outputs such as the phase angle value at the plateau, glassy modulus, rheological index and crossover frequency correctly predict the behavior of the neat and modified binders.