Study on the microscopic characteristics and rheological properties of thermal-oxidative aged and virgin-old recycled asphalts

[Display omitted] •The virgin-old recycling slowed the thermal-oxidative aging by physical approach.•The change in molecules affects the viscosity more than the fatigue performance.•The increase in viscosity was mainly attributed to macromolecules weight increased.•The proportion of the dispersion medium affected the fatigue resistance potential. This study aimed to investigate the thermal-oxidative aging and virgin-old recycling behavior of SBS polymer modified asphalt. For the same, the four-component method, the Fourier transform infrared spectroscopy (FTIR), and the gel permeation chromatography (GPC) test were adopted for characterizing five types of asphalt binders. Besides, Brookfield rotary viscosity and time scan tests were conducted for measuring the rheological parameters of the asphalt samples. The results indicated the following: (i) Thermal-oxidative aging deteriorated the fluidity and performance stability of the asphalt. The aromatic ring index, IC=C, was able to reflect the change in the temperature sensitivity of the asphalt during the process of aging. (ii) After thermal oxidation, the increase in viscosity was mainly attributed to the increase of asphalt macromolecules weight. A reduction in the proportion of the dispersion medium in the asphalt colloid structure was observed to be the main reason for its decreased fatigue resistance potential. (iii) By adding fresh asphalt, the virgin-old recycling approach slowed the thermal-oxidative aging, primarily due to physical integration. (iv) In this study, the asphalt viscosity-temperature properties were more sensitive to molecular changes than fatigue properties.