Analysis of nonlinear viscoelastic response of asphalt through multiple stress creep recovery test

The mechanical response of asphalt obtained from the multiple stress creep recovery (MSCR) test is of great significance to characterize its high-temperature performance. However, existing studies struggle to accurately determine the critical stress value for differentiating the linear viscoelastic and nonlinear viscoelastic stages of asphalt at different temperatures. To address this issue, this study conducts the MSCR test on five types of asphalt at different temperatures and employs the Schapery's nonlinear viscoelastic theory to analyze the mechanical behavior of each type of asphalt under varying temperatures and stress levels. Eventually, the critical stress at the linear viscoelastic, nonlinear viscoelastic, and damage stages of asphalt is distinguished according to the calculated nonlinear viscoelastic parameters. The results show that the critical stress for the transition from linear to nonlinear viscoelasticity can be initially identified by the overlap of the recovery creep compliance J_r under different stresses with that at the reference stress. When the calculated nonlinear viscoelastic parameter g₂ starts to decrease, the corresponding stress represents the critical stress between the linear and nonlinear viscoelastic stages. Furthermore, g₂ decreases with increasing stress and is closely related to the stress ratio. The nonlinear viscoelastic parameter g₁ tends to increase with the stress level, and when it reaches its maximum value, it indicates that the asphalt is about to enter the damage state. The critical stress σ_L-NL between the linear and nonlinear viscoelastic stages of asphalt shows an exponential function relationship with temperature, which can be used to predict the viscoelastic properties of asphalt at different temperatures.