Characterization of the shear-thinning behavior of asphalt binders with consideration of yield stress

Abstract

This study focused on characterizing the shear-thinning behavior of asphalt binders. The first objective was to identify the existence of yield stress behavior and to employ a rheological model to describe the flow curve of asphalt binders. The second objective was to verify the applicability of the Cox–Merz rule to asphalt binders with consideration of yield stress. A Dynamic Shear Rheometer (DSR) was employed to perform the frequency sweep test and the shear rate sweep test on three types of neat asphalt binders at 50, 60 and 70 °C. The test results of both tests confirmed the yield stress behavior of selected asphalt binders. The asphalt binders were then classified as the shear-thinning liquids with yield stress. As a result, the zero shear viscosity (ZSV), which was utilized as a rutting indicator, was not an indicator of the shear viscosity at zero shear rate but corresponded to the shear viscosity of a Newtonian plateau at low shear rates. A modified Carreau model was employed to characterize the shear-thinning behavior of asphalt binders, which demonstrated the ability to account for the yield stress behavior. The applicability of the Cox–Merz rule was examined by establishing the flow curve and the log–log plot of complex viscosity versus angular frequency in the same graph with respect to each replicate at each temperature. It was demonstrated that the Cox–Merz rule was followed in part of the ZSV region and part of the shear-thinning region but not followed in the yield stress region.