Applicability of the Cox–Merz relationship for asphalt binder

Asphalt binder has a critical effect on the performance of asphalt mixtures. Thus, asphalt binder is of great concern to pavement engineers and researchers. Usually, asphalt binder is studied in dynamic space and steady-state space separately, and the property indices are researched separately. As researchers delved deeper, they found that it is important to combine the dynamic properties and steady-state properties, especially for establishing rheological curves and constitutive equations. The Cox–Merz relationship can connect the properties in dynamic space to those in steady-state space. This relationship is widely used in polymer system and shows good results. This study focused on the applicability of the Cox–Merz relationship as it pertains to asphalt binder. The Cox–Merz relationship was applied to six neat asphalt binders. Then, the applicability of the Cox–Merz relationship for asphalt binder was studied and the criterion to verify whether the Cox–Merz relationship is followed or not was established. Finally the viscosity functions when the Cox–Merz relationship used were studied, and the Cross model and the Carreau model were compared. The results show that the Cox–Merz relationship is followed in the shear-thinning region and not always followed in the zero-shear-rate-limiting viscosity region, and it is useful when obtaining the viscosity function.

► The Cox–Merz relationship is followed in the shear-thinning range. ► The Cox–Merz relationship is not always followed in the zero-shear-rate-limiting viscosity region. ► The criterion to check whether the Cox–Merz relationship is suitable for asphalt binder or not was established. ► The Cox–Merz relationship is useful for obtaining the viscosity function of asphalt binder. ► Both of the Cross model and the Carreau model can be used to analyze the viscosity of asphalt binder.