AFM analysis of rejuvenated graphene nanoplatelets for nanoscale reinforcement and microwave-induced healing in asphalt binders

Understanding nanoscale mechanisms governing reinforcement and healing in asphalt binders is essential for developing durable pavements. This study investigates graphene nanoplatelets (GnP) and rejuvenator-infused graphene (GnP-Rej) in a PG 67–22 binder using PF-QNM atomic force microscopy under unaged, PAV-aged, and microwave-treated conditions. GnP refined binder morphology, reducing surface roughness from ∼2.1 nm to ∼1.44 nm at 0.24 wt% and increasing stiffness through molecular confinement, with saturation beyond ∼0.1 wt% due to agglomeration. Aging increased peri- and para-phase modulus by ∼68% and ∼61%, respectively, while GnP and GnP-Rej mitigated these effects. GnP-Rej exhibited dual-function behavior, enhancing local compliance and interfacial mobility. Microwave activation increased adhesion by up to ∼51% without significant modulus change. The adhesion-based healing index confirmed consistent nanoscale recovery, with maximum healing observed at 0.24 wt% GnP-Rej. These results indicate that healing is governed by adhesion-controlled nanoscale recovery and provide mechanistic insight into the relationship between nanoscale behavior and improved asphalt performance.