Synergistic effect of polymer‐modified rejuvenator and fresh asphalt on road performance of hot in‐place recycling styrene–butadiene–styrene‐modified asphalt mixtures

Abstract To enhance the road performance of hot in‐place recycling (HIR) styrene–butadiene–styrene (SBS)‐modified asphalt mixtures, this paper investigates the recycling effects of polymer‐modified rejuvenator (PMRA) and fresh SBS‐modified asphalt under synergistic conditions, comparing them with a conventional commercial rejuvenator. The rheological properties of the recycled asphalt binder were assessed using a dynamic shear rheometer and bending beam rheometer. Microscopic characteristics were examined through fluorescence microscopy, Fourier transform infrared spectroscopy and gel permeation chromatography. Road performance was evaluated at the mixture level using rutting tests, low‐temperature bending beam tests and semi‐circular bending tests. The results indicate that 6% PMRA not only enhances the low‐temperature performance and fatigue resistance of recycled asphalt binder but also maintains excellent high‐temperature performance with low stress sensitivity. Furthermore, PMRA recycled mixtures can reduce rutting depth and significantly improve maximum bending strain and fracture energy, compensating for the low‐temperature crack resistance deficiency of HIR mixtures. Despite being a form of physical regeneration, PMRA incorporates aromatic oil and softeners to replenish volatile light components and provides a swelling environment. The supplemental SBS helps reconstruct the damaged polymer network. However, adding fresh asphalt may dilute the recycling effect and reduce the degree of fusion between aged and new asphalt, ultimately decreasing fatigue life. Therefore, this paper recommends 20% fresh asphalt content and 6% PMRA. © 2024 Society of Chemical Industry.