On the rejuvenator dosage optimization for aged SBS modified bitumen

The rejuvenator dosage in bituminous binders is critical, as it has to be balanced to ensure the restoration of rheological properties without over-softening the recycled binders. In this study, the impact of dosage of different rejuvenators on a polymer modified bitumen was evaluated by conducting rheological tests at low, medium and high temperatures using a dynamic shear rheometer. This paper also presents the results from a differential scanning calorimetry in an effort to assess the glass transition of new recycled binders. The results indicate that the complex modulus and phase angle, Glover-Rowe parameter and glass transition temperature can be successfully used to evaluate the effectiveness of rejuvenators. Moreover, the maximum and minimum rejuvenator dosage was selected by performing multiple stress creep recovery and frequency sweep tests, respectively, and particularly by balancing between creep compliance and complex modulus results. Compared with the commercial rejuvenators, the lab prepared rejuvenator can effectively recover the cracking and fatigue resistance, without dramatically scarifying the rutting resistance. Overall, a procedure was proposed to select the appropriate dosage and type of rejuvenator for polymer modified binders toward engineering durable and long-lasting recycled pavement materials.