A viscoelastic model and structural properties of Sasobit-modified asphalt

Sasobit is an additive to produce asphalt mixes suitable for the use at lower construction temperatures without sacrificing the mix properties. However, Sasobit damages the time–temperature superposition principle (TTSP) of asphalt. Therefore, it is difficult to characterize the constitutive equation of Sasobit-modified asphalt. This study has modeled the rheological response of Sasobit-modified bitumen (two types) using a combination of two different models that describe gel-asphalt and sol-asphalt, respectively. Sasobit-modified asphalt is cooled after heating, the wax forms a crystal network structure, and gel-asphalt is obtained. The creep process of Sasobit-modified asphalt can be described by a nonlinear model, which is accompanied by the damage of the network structure, and thus, sol-asphalt is obtained. The network structure change of the wax in the asphalt may explain the mechanism of deviation from TTSP, and the structural characteristics of Sasobit-modified asphalt could be clearly described by the combined model. This will provide a foundation for accurately acquiring the rheological properties of Sasobit-modified asphalt.