Use of Highly Modified Asphalt and Rejuvenators to Restore the Rheological and Mechanical Properties of Aged Polymer-Modified Bitumen

Hot recycling is a common solution to reuse reclaimed asphalt pavement (RAP) due to its considerable environmental and economic advantages. However, when a new mix with polymer-modified bitumen (PmB) has to be produced, the lack/degradation of the styrene–butadiene–styrene (SBS) in the RAP bitumen has to be managed. To this aim, a highly modified asphalt (HiMA™) binder, including an asphalt recycling agent (ARA), was investigated. A blend containing 50% of RAP bitumen and 50% of rejuvenating HiMA was compared with a virgin PmB and a blend of 50% PmB, 50% RAP bitumen, and an ARA. The experimental program involved the frequency sweep test, the multiple stress creep recovery (MSCR) test, and the linear amplitude sweep (LAS) test using a dynamic shear rheometer. The results showed that the ARA allowed obtaining adequate stiffness of the recycled blend but did not fully restore the rheological properties and the resistance to fatigue. In the HiMA, the high dosage of SBS polymers and the presence of the ARA entailed suitable stiffness at all service temperatures, marked elastic features and ductility, and an excellent performance against permanent deformations.