Assessment of Asphalt Aging Degree Using the Double Sigmoidal Rheological Master Curve Model

The master curve is widely used in the evaluation of rheological behavior asphalt. However, due to the complex rheological properties of high-viscosity modified asphalt (HVMA), its rheological properties change significantly after aging, and the existing master curve models cannot adequately fit the HVMA binder before and after aging. Therefore, this study first introduces the double sigmoidal model, which has shown good fitting results for polymer-modified asphalt binder in recent years, to evaluate HVMA at different aging levels and compares it with classical models such as the Christensen–Anderson–Marasteanu and sigmoidal models. The results indicate that the double sigmoidal model demonstrates stronger universality in fitting asphalt before and after aging. Based on the double sigmoidal model, the parameters γ1 and β1 of the master curve model are proposed to evaluate the aging of HVMA, respectively. The results show that γ1 can characterize the hardening of the asphalt phase, with lower values indicating more severe asphalt aging, while β1 gradually decreases during the aging process, reflecting the degradation of the polymer. Further calculation of the phase angle extreme point reveals that due to the destruction of the polymer cross-linking network caused by aging, the temperature sensitivity of HVMA increases, and the phase angle extreme point shows an increasing trend. Finally, the changes in the carbonyl index (ICA) of asphalt before and after aging are calculated using semiquantitative analysis by infrared spectroscopy and correlate IB/S index with the aging evaluation indicators based on the model parameters mentioned above. The two evaluation methods have a significant correlation.