Analysis of viscoelastic response and creep deformation mechanism of asphalt mixture

Asphalt mixture is a typical viscoelastic material. Its mechanical response and deformation behavior depend on the role of time, temperature conditions and stress levels. Three kinds of asphalt mixture (i.e. AC-13, AC-16, AC-20) were used for the static creep test in different temperature conditions and stress levels. According to the creep curve, The Burgers viscoelastic parameters including E1, η1, E2, η2 and the steady-state creep rate K were obtained. The effects of test temperature, stress level and aggregate gradation on the viscoelastic parameters of asphalt mixture were analyzed. Based on the relationship between the steady-state creep rate and the experimental temperature & load stress, the stress index and creep activation energy of asphalt mixture were proposed. By analyzing the relationship between the creep activation energy and the rutting depth, the creep mechanism of the asphalt mixture was discussed. The results show that with the increase of temperature, the four parameters of E1, η1, E2 and η2 of the three kinds of asphalt mixtures generally decrease. But at different temperatures, the viscoelastic parameters of these three kinds of mixtures are not the same. The stress level has a significant effect on the viscoelastic properties of the asphalt mixture. The four viscoelastic parameters have the largest differences when the stress level is at the intermediate load level of 0.5 MPa, but the responses of the different gradation asphalt mixture to the stress level are different. With the increase of temperature and load stress, the steady-state creep rate increases gradually, but the stress indexes of these three kinds of asphalt mixtures stress index are not different. All of them are less than 3, and belong to the diffusion creep under the control of aggregate interface dislocation mechanism. The asphalt mixture that has larger creep activation energy has better stability under high temperature. AC-16 mixture has the highest creep activation energy. Nominal particle size is not a decisive factor for the performance in high temperature.