Morphological, Thermal, and Mechanical Properties of Asphalt Binders Modified by Graphene and Carbon Nanotube

Abstract

The mechanical behavior of asphalt concrete varies with temperature; therefore, researchers have been developing technologies to reduce temperature fluctuations in pavement overlays. Increasing the thermal conductivity of asphalt concrete is a key component in the realization of these technologies. Previous studies have introduced, among other additives, carbon nanotubes (CNTs), graphite, graphene nanoplatelets (GNPs), and copper slag to asphalt binders/concrete to enhance their thermal-physical properties. However, it has been challenging to assess the distribution of these additives in asphalt materials. In this paper, binary (i.e., binder/CNT and binder/GNP) and ternary (i.e., binder/CNT/GNP) composites were prepared by pretreating the additives with a surfactant and through sonication, before they were mixed into the hot binder using a mechanical shear mixer. Morphology and dispersion uniformity of CNTs and GNPs in the binders were evaluated using a digital microscope and scanning electron microscopy (SEM). The thermal conductivity of these samples was measured using Nanoflash combined with differential scanning calorimetry. The rheological properties were tested using rheometry. Results showed that our sample preparation method was able to uniformly disperse the CNTs and GNPs in the binder, as seen in the digital microscope images that offered more representative morphologies of asphalt binders than SEM. The addition of CNTs (0%–2% by weight) and/or GNPs (0%–15% by weight) improved the binder’s thermal conductivity at a limited degree, whereas the rheological properties of the CNT/GNP-modified binders remained very close to those of the control sample. Findings from this work may provide some insights into the development of new asphalt materials as well as other CNT/GNP-based composites.