Towards very high RAP content asphalt mixes: A comprehensive performance-based study of rejuvenated binders

Abstract

Hot recycling of reclaimed asphalt pavement (RAP) from replacement of deteriorated asphalt pavements is a widespread technique, and able to ensure clear economic and environmental benefits. For this reason, paving industries, agencies and researchers are spending significant efforts in order to maximize such advantages by increasing the amount of RAP within new asphalt mixtures. Nevertheless, adequate performance of recycled mixtures must be guaranteed despite the re-use of high amounts of RAP which involves the presence of aged, oxidized and stiffened binder. In this perspective, the present study aimed at evaluating the rheological properties at mid-service and high-service temperatures of bituminous blends composed by 40% of virgin binder and 60% of aged rejuvenated bitumen (simulating the aged hard bitumen coming from the RAP). Such proportion was selected to represent a high recycling rate of RAP (about 60% of the total weight of aggregates, RAP included). A chemical commercial additive at the liquid state was selected as rejuvenator; it was dosed at the optimum content based on empirical and rheological preliminary characterization. The performance of the recycled blend was then compared to that of a virgin reference bitumen. Dynamic shear rheometer tests were carried out to determine the master curves and the failure characteristics (at mid and high service temperatures) of the selected binders. The effect of aging (related to the durability over the material lifetime) was also studied analyzing binders’ responses in unaged, short-term and long-term aged conditions. Overall, experimental findings demonstrated the efficacy of the rejuvenation of recycled binders containing very high amount of aged bitumen.

Keywords

• Pavement engineering
• Hot recycling
• Reclaimed asphalt
• Rejuvenation
• DSR
• Rheology