Using viscosity models to predict the properties of rejuvenated reclaimed asphalt pavement (RAP) binders

The use of rejuvenators in mixes with high reclaimed asphalt pavement (RAP) content is becoming common practice. Rejuvenators are added to mixes containing RAP to reduce the stiffness of the RAP binders and improve their low temperature properties hence allowing for higher amounts of RAP to be included in the mix. For RAP mixes utilising more than 25% RAP, blending charts are often used to determine the proportions of the virgin and RAP binders based on their respective performance grades. Introducing rejuvenators into the blend changes the overall physical properties of the blend, hence the need to assess the validity of blending charts when rejuvenators are present. In this paper, the rheological properties of a soybean-derived rejuvenator are studied using a rotational viscometer. Asphalt blends made with an extracted RAP, a virgin PG58-28 binder, and a soybean-derived rejuvenator are prepared using different proportions. The performance grades of the extracted and recovered RAP and the resulting rejuvenated RAP blends are determined using a dynamic shear rheometer (DSR) and a bending beam rheometer (BBR). The results revealed that the rejuvenator successfully reduced both the high and low temperature performance grades of the control blend. The impact of the rejuvenator on the viscosity of the blend is studied and two different viscosity models were used to predict the blend viscosity. The models were shown to be valid for binder blends made with RAP binder and rejuvenated virgin binders. The models also provided a fair prediction of the viscosity of the 3% rejuvenated virgin binder but could not accurately predict the viscosity of the 6% rejuvenated virgin binder.