Investigating the effectiveness of carbon nanomaterials on asphalt binders from hot storage stability, thermodynamics, and mechanism perspectives

Abstract

The utilization of carbon nanomaterials such as graphene oxide (GO) and carbon nanotube (CNT) to modify asphalt binders is an innovative process. The feasibility of modifying asphalt binder with carbon nanomaterials was evaluated from the perspectives of storage stability, thermodynamic property, thermal stability and chemical structure. Accordingly, a combination of the segregation tests, dynamic mechanical rheological analyses and micro-morphology observation methods were adopted to verify whether the carbon-based nanoparticles could possibly segregate in the asphalt binders. The sessile drop method based on the surface free energy (SFE) theory was utilized to calculate the thermodynamic parameters of carbon nanomaterials-modified binders and the aggregates, and the effect of aging on the thermodynamic characteristics of the modified binders was evaluated. Moreover, the thermal gravimetric analysis (TGA) was performed to assess the effect of GO and CNT on the thermal characteristics of the binders. Finally, changes in the chemical structure were detected via Fourier transform infrared (FTIR) spectroscopy. The physical tests of the softening point differences, the rheological responses and the microscopic morphologies showed that the carbon nanomaterial-modified binders could achieve storage stability characteristics. The results of the SFE and related parameters suggested that the carbon-based nanoparticles can promote the thermodynamic characteristics of the asphalt binder. The rolling thin film oven (RTFO) process promoted the thermodynamic properties of the modified binders while the 12-day ultraviolet aging had an adverse effectiveness on the thermodynamic properties of the modified binders. For TGA tests, three indicators such as the residues at 600 °C revealed that CNT enhanced the thermal stability of the binders while GO weakened the thermal characteristics of the binders. The FTIR data demonstrated that no chemical reactions occurred in the process of preparing carbon nanomaterial-modified binders.