Research On Rheological Characteristics And Fatigue Of Conductive Asphalt Concrete

Conductive asphalt concrete (CAC) is prepared by adding the conductive fillers, such as graphite and carbon fiber, into the ordinary asphalt concrete to make the ordinary asphalt concrete with the performances of electrical and thermal conductivity. With the original electrothermal effect of asphalt pavement, The CAC can melt snow and ice on the pavement to avoid traffic accident in winter.As the concuctive fillers are applied in the asphalt mixture, the interaction between graphite and carbon fiber will influence the pavement mechanical performaces, especially rutting and fatigue resistance because high specific surface area, excellent physical absorbing asphalt and lubrication of graphite will destroy performances of asphalt concrete while the enhancement of carbon fiber will improve performances of asphalt concrete. It is necessary to research mechanical properties of CAC if the CAC is applied in the practical projects. Around the fatigue and rheology performances of asphalt concrete, the related experiments were carried out in this paper, and the corresponding models were developed to provide mechanical parameters of materials for the mechanical calculation of pavement structure.In this paper, research on rheological performances of CAC was implemented by dynamic modulus and creep experiments. Under the conditions of temperature-10℃-60℃and frequency 0.1Hz-25 Hz, the dynamic modulus experiment was carried out to obtain the data which were used to model the dynamic master curve. The result indicates that the addition of conductive fillers not only improves the performace of rutting resistance of asphalt concrete at high temperature, but also enhances the performance of deformation resistance while causing flexible modulus decrease and crisp damage at low temperature. From shift factors for dynamic modulus masters curve, the addition of conductive fillers improves sensibility to temperature for asphalt concrete.The comparison were carried out between single axial static creep test and rutting test and the result shows that Burgers model can interpret viscoelastic behavior of asphalt concrete during loading phase accurately, after the conductive fillers are added, the parameters E1,E2,η2 of Burgers model are increased significantly whileη1 is not effected; the performance of rutting resistance is increased by the addition of conductive fillers.Research on the fatigue of CAC is conducted by four-point bending fatigue test. Based on the three exsisting fatigue models:Strain-dependent fatigue model, strain and initial mix stiffness-dependent fatigue model, dissipated energy-dependent fatigue model, the fatigue performance of asphalt concrete can be researched by the three fatigue models parameters which are modeled by nonlinear least square method. According to strain-dependent fatigue model, the CAC fatigue life is shorter than the control due to the addition of conductive fillers. According to strain and initial mix stiffness-dependent fatigue model, the fatigue lives decrease with increasing strain levels and initial mix stiffness; At low temperature(5℃), the fatigue life of CAC decreases more rapidly with increasing initial mix stiffness than the control, however, at middle temperature (15℃), the change of the CAC fatigue life is the opposite; According to dissipated energy-dependent fatigue model, the addition of conductive makes the energy of asphalt concrete dissipate more rapidly at low or middle temperature, the increased dissipated energy is not help to improve fatigue performace of asphalt concrete.