Effects of Surface Area and Particle Size of Graphite and Graphene Nanoplatelets on Their Oxidation and Subsequent Use in the Modification of Asphalt Binder

Graphene oxide (GO) has gained significant attention for its unique physical and chemical properties. GO finds application in a wide range of fields, including biomedicine, electronics, energy, and the environment. It also plays a significant role in the modification of infrastructure materials, such as asphalt and cement, in civil engineering. In this study, we report on the synthesis of GOs from graphite (Gr) powder and graphene nanoplatelets (GNPs) using an improved Hummers’ method. We extensively investigated the effects of particle size and specific surface area of the Gr and GNP precursors on their oxidation, which have not been addressed in literature. The results from Fourier-transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses show that the GO made from Gr powder with a large surface area and small size has a higher degree of oxidation with about 9.8% carboxyl functional groups. This provides more opportunities for interactions with different molecules, including asphalt components. In this regard, we investigated the impact of carboxyl-rich GO (higher oxidation percentage) on the high-temperature performance of asphalt binder through rotational viscosity, rheology, multiple stress creep and recovery (MSCR), and anti-aging property measurements. Our experimental results indicate that GO obtained from the Gr powder precursor (designated ox-Gr) can significantly improve the high-temperature performance of asphalt binder. For example, the introduction of only 2 wt.% GO to a performance grade asphalt binder (PG 67-22) can dramatically increase its complex shear modulus (G*), as well as decrease the phase angle (δ), at high temperatures. The MSCR tests showed that the addition of GO to asphalt binder effectively mitigates its permanent deformation and improves its elastic response, as demonstrated by about 39% reduction in the creep compliance (J_nr) and an impressive 297% increase in the percent recovery (εR) of the GO-modified binder. Furthermore, the measured viscosity aging index and G* ratio of the GO-modified asphalt binder confirm the significant effect of GO on the improvement of the anti-aging properties of the binder.