Analysis Of Nonlinear Viscoelastic Creep Behaviour Of Hot-mix Asphalt

Recently, more and more researchers and engineers have a strong pull on the works about the pavement distresses, and try to predict the response of pavement to temperature, loading, frequency and other factors by employing some mathematical models. With the pavement distresses about rutting and upheaval related to the nonlinear viscoelastic property of HMA, well-established nonlinear models are theoretically significant and valuable in application.In this study, the viscoelastic creep behaviour of a hot-mix asphalt was experimentally investigated by creep tests and analyses, and several nonlinear viscoelastic models were compared in parallel. A static pressing and modelling machine is developed to prepare the certain cylindrical specimen with a larger ratio of hight to diameter. The uniaxial compressive creep tests, subjected to eight given stress levels from 0.1 MPa to 0.8 MPa, were conducted via a MTS 809 axial/torsional test system.The compressive creep compliance curves shows that the creep compliance magnitude and its increment tend to decrease as the applied stress increases, and that the HMA is a type of nonlinear viscoelastic material under given conditions. This were mainly caused by the compaction of specimens and the enlargement of the cross sectional area under compression. Besides, the instantaneous creep strain is proportional to the applied stress level, which is the so-called instantaneous elasticity.The Findley model, the simplified multiple integral model and the modified time-hardening model were then employed to describe the creep behaviour of HMA within the first two creep stages. Further, flexibility as well as goodness and workload were proposed to competitively evaluate the practicability of these models. It could be concluded that Findley model was superior to the others, and that the simplified multiple integral model was not so good to model the viscoelastic creep behaviour of the hot-mix asphalt. Moreover, the comparison between the time-hardening model and the modified one was done. In the case of short-term prediction, the modified time-hardening model is better than the time-hardening model in characterization of the nonlinear creep behaviour. In the case of long-term prediction, there is little difference. Besides, the Findley model was evolved to the case of linear loading, and the time-hardening model was used to predict the displacement of old cement concrete pavement with asphalt overlay.