Carbon nanotube-modified bio-oil recycled asphalt: A laboratory study for efficient aged binder rejuvenation

To sufficiently improve the inadequate high-temperature performance of bio-oil recycled asphalt, carbon nanotube (CNTs) was used to modify the bio-oil regenerated aged asphalt in this research. First, the effects of bio-oil content, CNTs content, and shearing time were considered. Using softening point, ductility, penetration, and viscosity as response indicators, the best preparation process for carbon nanotube modified bio-oil recycled aged asphalt (CMBRA) was determined using the response surface methodology. Further verified its optimal blending ratio through rheological performance tests. The optimal contents of bio-oil and CNTs were 5.821% and 0.598%, respectively. The optimal shearing time was 29.675 minutes. Its water stability and storage stability were evaluated through water-boiling tests and storage stability tests. The modification mechanism, distribution state, and effect of carbon nanotubes in bio-oil recycled aged asphalt were investigated using Fourier transform infrared spectroscopy (FTIR), fluorescence microscopy (FM), and atomic force microscopy (AFM). The thermal stability of CMBRA was analyzed through thermogravimetric analysis (TGA). The results showed that carbon nanotubes effectively enhanced the rutting factor of bio-oil regenerated aged asphalt and improved its high-temperature performance, and exhibited excellent moisture stability and storage stability. However, an excessive dosage negatively impacted its low-temperature performance. The addition of carbon nanotubes formed a colloidal structure in bio-oil recycled asphalt, significantly improving its compatibility. Compared to bio-oil recycled aged asphalt, CMBRA did not generate any new functional groups. The honeycomb structure in CMBRA was significantly fewer than in bio-oil recycled aged asphalt, indicating that the adsorption force between the asphaltenes was notably enhanced. The colloidal structure formed by the addition of carbon nanotubes effectively improved the thermal stability of bio-oil recycled asphalt. This study provided a theoretical foundation and technical approach for the efficient recycling of aged asphalt using CNTs, demonstrating significant potential for sustainable pavement maintenance. • CNTs were used to enhance the high-temperature performance of recycled asphalt. • Response surface methodology optimized the preparation of CMBRA. • CNTs formed a stable colloidal structure and improved thermal stability.