Dispersion, compatibility, and rheological properties of graphene-modified asphalt binders

Graphene is a 2D nanomaterial made of a monolayer, honeycomb lattice structure established by sp2-hybridized carbon atoms. Previous studies have indicated that graphene enhanced the high- temperature performance of neat asphalt binders. However, the intermediate- and low-temperature performance, dispersion, and compatibility of graphene-modified asphalt binders remain unclear. This study presents a comprehensive investigation on the above-mentioned research gaps of graphene-modified asphalt binders. A commercially available graphene was mixed with non-modified binder and SBS modified binder. The graphene dosage was varied as 0%, 0.3%, 0.65%, 1%, 1.5%, 2.5%, 5%, and 7% by the total weight of blends. The graphene dispersion was assessed by direct observation with an optical microscope and quantitative calculation through 2D image processing. The rotational viscosimeter was used to measure viscosity and to analyze the workability. The cigar tube test was conducted to examine the compatibility between graphene and asphalt binders. The Dynamic Shear Rheometer test was carried out on unaged, RTFO-aged, and PAV-aged specimens to obtain the rheological properties as well as to analyze the high- and intermediate-temperature performance. The bending beam rheometer was used to study the thermal cracking resistance at low temperature. The results showed that graphene up to 1.5% dosage was well dispersed in asphalt binders. The addition of graphene up to 1% dosage slightly increased the viscosity of asphalt binders. There was good compatibility between graphene and asphalt binders. Graphene significantly improved the rutting resistance, while had little adverse influence on the fatigue cracking and thermal cracking resistance up to 0.65% dosage addition. Thus, the optimum graphene dosage was 0.65% for both binder types. The findings showed the promising application of graphene in asphalt pavements.