Research on the mesoscopic viscoelastic property of semi-flexible pavement mixture based on discrete element simulation

Semi-flexible pavement (SFP) mixture is a relatively new pavement material that combines the characteristics of the flexibility of asphalt mixtures and the rigidity of cement concrete. In this research, the discrete element method was used to reveal the viscoelastic mechanical behavior mechanism of the SFP mixture at a mesoscopic scale. First, the influence of the matrix asphalt mixture air voids on the viscoelastic performance of the SFP mixture was studied through laboratory tests to clarify its basic macroscopic mechanical properties. The results showed that the SFP mixture combines good high and low temperature performances when the air void is 25%. Then, the discrete element simulation software PFC3D was applied to establish an SFP mixture model, and the simulation of the dynamic modulus test and uniaxial compression creep test was conducted to study the mesoscopic mechanical composition and force evolution. The results demonstrated that when subjected to dynamic loading, each constituent inside the SFP mixture is subjected to compressive forces, most of which are borne by the internal contact of aggregate-aggregate, while the tensile forces are mainly borne by the contacts of asphalt mortar-asphalt mortar, cement stone-cement stone, and aggregate-asphalt mortar. When subjected to a constant static loading, the value order of the contact force in the SFP mixture is: aggregate-aggregate > cement stone-cement stone > aggregate-asphalt mortar > asphalt mortar-cement stone > cement stone-aggregate > asphalt mortar-asphalt mortar. As the creep progresses, the contact force of aggregate-aggregate increases slightly; the contact forces of cement stone-cement stone, aggregate-asphalt mortar, and cement stone-aggregate decrease slightly; and the contact forces of asphalt mortar-asphalt mortar and asphalt mortar-cement stone decrease rapidly.