Development of the generalised SPD model for linear viscoelastic characterisation of asphalt binders

This study intended to develop an analogical model to better characterise the phase angle master curves of asphalt binders, especially polymer-modified asphalt binders. Seven PAV-aged and two unaged asphalt binders were subjected to frequency sweep tests in the temperature range of 10-70 degrees C using a discovery hybrid rheometer. Four distinctive shape patterns were identified from the resulting phase angle master curves. The CAM model and the 2S2P1D model were first evaluated in terms of phase angle fitting accuracy. However, neither the CAM model nor the 2S2P1D model could accurately characterise the phase angle master curves of all shape patterns. Afterwards, a new analogical model was developed based on the generalisation of the 2S2P1D model, referred to as the generalised SPD model, which consists of a spring and multiple 1S2P1D models in parallel. It was found that the generalised SPD model outperformed the CAM model and the 2S2P1D model in its ability to precisely characterise the phase angle master curves of different shape patterns. It is recommended to use the generalised SPD model for master curve construction when the measured phase angle decreases significantly with decreasing frequency at high temperatures; in other cases, the 2S2P1D model remains applicable.