Rheological Properties and Mechanism of Asphalt Modified with Polypropylene and Graphene and Carbon Black Composites

The application of polypropylene (PP) to asphalt pavement construction, as one of the measures to dispose white waste, has suffered from many challenges. Meanwhile, the emerging nanomaterials for asphalt pavements has exhibited great potential and drawn the attention of many researchers. Therefore, in this study, the novel graphene/carbon black nanocomposite (GC) was selected to improve this dilemma by compounding with PP in different approaches. First, three kinds of asphalt binders incorporated with PP and GC were prepared by mechanical mixing. Subsequently, the temperature sweep, frequency sweep, multiple stress creep recovery (MSCR), and linear amplitude sweep (LAS) have been performed to evaluate the rheological properties of PP/GC composite-modified asphalt binders. In addition, the low-temperature tensile fracture behaviors of the different modified asphalt were investigated through the force-ductility testing machine (FDTM). Moreover, the microstructure and chemical composition of the different modified asphalt binders were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The experimental results confirmed that PP and GC synergistically increased the mechanical strength and high-temperature rutting resistance of the asphalt binder. As a result, the incorporation of GC significantly improved the stress sensitivity of the PP/CG composite-modified asphalt under repeated loading. Wherein, the polypropylene/GC masterbatch (PGC) modified asphalt, prepared by premixing process, exhibited superior fatigue-damage tolerance and low-temperature cracking resistance. SEM and FT-IR data revealed that the addition of GC facilitated the formation of a strong network structure of PP in the asphalt matrix by physical coblending. This study may cast some light on the application of PP and GC for asphalt modification.