Rheological Characterization of Recycled Asphalt Binders and Correlating the Zero Shear Viscosity to the Superpave Rutting Parameter

Abstract

The rheological behavior of recycled asphalt binders is important in the design of the optimum content of reclaimed asphalt pavement (RAP) material to be used in highway recycling projects. In this study, oscillatory tests were performed on recycled binders of varying RAP concentrations. The complex modulus master curves were constructed using the time–temperature superposition principle. The zero shear viscosities (ZSVs) were estimated using the Carreau–Yasuda model on the complex viscosity master curves for all the recycled binder combinations. It was found that the activation energy of flow changed linearly from 115.1 to 185.8 kJ/mol with an increase in the RAP content, whereas ZSV varied exponentially with an increase in the RAP content. A good correlation was found between the ZSV and the Superpave rutting parameter (G*/sinδ). An equation was derived to predict the G*/sinδ at any RAP concentration and temperature. For practical use, a G*/sinδ contour plot approach is introduced to calculate directly the maximum and minimum RAP content for any target binder grade suitable for the construction site. cA noticeable change in rheological behavior of recycled binders was observed on either side of the 40% RAP incorporation level.