Abstract
The mechanical behavior of asphalt mixture under high stresses presents nonlinear viscoelasticity and permanent deformation. In this paper, a nonlinear fractional viscoelastic plastic (NFVEP) creep model for asphalt mixture is proposed based on the Nishihara model, with a Koeller spring-pot replacing the Newton dashpot. The NFVEP model considers the instantaneous elasticity, viscoelasticity with damage and time-hardening viscoplasticity with damage concurrently, and the viscoelastic response is modeled by fractional derivative viscoelasticity. To verify the model, uniaxial compressive creep tests under various stresses ranging from 0.4 MPa to 0.8 MPa were carried out at room temperature. The NFVEP model predictions are in good agreement with the experiments. The comparison with the modified Nishihara model and the Burgers model reveals the advantages of the NFVEP model. The results show that the NFVEP model, with the same set of parameters, can not only describe the primary and steady-state creep stages of asphalt mixture under low stress levels but also the whole creep process, including the tertiary creep stage, of asphalt mixture under high stress levels.
Highlights
Hot mixed asphalt (HMA) mixture is one of the most widely used pavement materials and has remarkable viscoelastic properties [1]
The aim of this paper is to propose a nonlinear viscoelastic-plastic creep model to analyze and describe the creep behavior of asphalt mixtures at different stress levels by taking the viscoelasticity, viscoplasticity and stress-induced damage evolution into consideration
The curves indicate that when the stress level is relatively low, the creep presents only two stages: the primary creep stage and the steady-state creep stage
Summary
Hot mixed asphalt (HMA) mixture is one of the most widely used pavement materials and has remarkable viscoelastic properties [1]. Its mechanical behavior exhibits obvious time dependency, temperature dependency and load frequency dependency. Theoretical and experimental studies on its creep, stress relaxation and dynamic mechanical behaviors have provided a crucial foundation for pavement design. The viscoelasticity of materials can be divided into two categories: linear viscoelasticity and nonlinear viscoelasticity [1,2,3]. It can be distinguished by creep tests at different stress levels. If the creep compliance curve is independent of the applied creep stress, that is, the creep strain is proportional to the creep stress, the material is linearly viscoelastic; otherwise, the material is nonlinearly viscoelastic
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