Creep Damage Characteristics of Two Types of Dense-Graded Polyurethane Mixtures

Because of their better resistance to rutting, polyurethane mixtures have been used on certain road sections to replace pavement asphalt mixtures. However, the understanding of the corresponding mechanical mechanism behind it is not fully understood. In this work, a viscoelastic–elastoplastic mechanical model was developed to analyze changes in viscoelastic plasticity and damage development in two types of dense-graded polyurethane mixtures with different polyurethane binders. A constitutive equation for creep compliance was derived, with a damage variable defined based on creep compliance. Creep and creep recovery tests were conducted on the two types of dense-graded polyurethane mixtures to obtain changes in their creep mechanical properties under varying stress and temperature levels. The mechanical parameters of the established model were determined using graphical and fitting methods, which were then used to investigate the impact of creep damage on the creep and creep recovery rate of the mixtures under different influencing factors. The proposed damage variable was employed to represent the viscoelastic–plastic mechanical behavior of the mixtures at varying stress levels. Subsequently, the evolution characteristics of creep damage in the viscoelastic–plastic mechanical properties of the mixtures were examined, along with the differential impact of creep damage on the viscosity and elasticity of the mixtures.