Improved Oxidation of Graphite and Graphene Nanoplatelets: Application to the Modification of Asphalt Binder

Graphene oxide (GO) and its derivatives find application in fields such as biomedicine, electronics, energy, and the environment. They also play a significant role in the modification of infrastructure materials, such as asphalt and cement. In this study, we oxidized commercially available graphite (Gr) powder and graphene nanoplatelets (GNPs) using an improved Hummers' method. We first investigated the effects of particle sizes and specific surface areas of the Gr and GNP precursors on their oxidation, which have not been addressed in literature. The results from Fourier transform infrared and X-ray photoelectron spectroscopy analyses show that oxidized Gr (designated ox-Gr or simply GO) with a large surface area and small particle size has a higher degree of oxidation than that of oxidized GNPs (designated oxidized multilayer graphene) with about 9.8% carboxyl functional groups that provide favorable interactions with asphalt binder components. Next, we investigated the effect of this carboxyl-rich GO on the high-temperature performance of the asphalt binder through rotational viscosity, rheology, multiple stress creep and recovery (MSCR), and antiaging property measurements. Our results indicate that 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 (delta), at high temperatures. The MSCR tests show that the addition of GO to the asphalt binder effectively mitigates its permanent deformation and improves its elastic response, as demonstrated by a reduction of about 39% in the creep compliance (J( nr)) and an impressive 297% increase in the percent recovery (epsilon R) 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 antiaging properties of the binder.