New Predictive Models for Viscosity and Complex Shear Modulus of Asphalt Binders

Abstract

The main purpose of this paper is to present the development of a set of predictive models for the viscosity and complex shear modulus of asphalt binders. The model development was aimed at overcoming the limitations of current models used in the Mechanistic-Empirical Pavement Design Guide (MEPDG), which has been developed under NCHRP Project 1-37A and refined under NCHRP Project 1-40D. A comprehensive study was completed at Arizona State University to conduct a number of asphalt binder tests and to finalize a large binder characterization database containing 8,940 data points from 41 different virgin and modified binders. This database was used to develop the new models. The first of the models developed in this study is a fully revised version of the widely known ASTM Ai-VTSi viscosity model. This new, revised model takes into account the loading frequency applied on the binder while accurately predicting the viscosity at a specific temperature and loading frequency from the Ai and VTSi values of a binder. The other two new models developed are capable of accurately predicting the dynamic shear modulus (|G*b|) and associated phase angle (δb) of the binder at a specific temperature and loading frequency from the Ai and VTSi values of the binder. The models have been found to be rational, unbiased, accurate, and statistically sound. It is hypothesized that because of mathematical structures similar to those used in the MEPDG, the models developed in this study can be incorporated easily into a future revision of the guide.