Mechanical properties evaluation of crumb rubber asphalt mixture for elastic trackbed

As a new type of railway structure, the elastic trackbed can avoid the inherent limitations of railway ballast tracks and slab tracks. Therefore, it is of great significance to provide excellent materials for the elastic trackbed. In this paper, the feasibility of applying crumb rubber asphalt mixture (CRM) to the railway trackbed is preliminarily investigated by evaluating the mechanical properties of CRM. The static modulus, vertical deformation and lateral stability of CRM for the elastic trackbed are characterized via the uniaxial compression test as well as the interfacial shear test. In addition, via the dynamic creep test, the temperature susceptibility, the viscoelastic behaviours as well as the creep compliance master curve of CRM are studied. The uniaxial compression results show that the stiffness of CRM with 3 wt% and 6 wt% crumb rubber particles decreases compared with the ordinary asphalt mixture. And the vertical deformation can also meet the requirements of the elastic trackbed. Furthermore, it is shown from the shear test that the interfacial strength, which presents a linear relationship with temperature, can provide satisfactory lateral stability of the elastic trackbed. Additionally, the dynamic creep test results reveal that the addition of 3 wt% crumb rubber will not lead to excessive accumulation and the increased temperature susceptibility of permanent deformation at high temperature. The viscoelastic parameters gained from the dynamic creep test also show that asphalt mixture with 6 wt% crumb rubber particles shows the worst resistance to deformation despite having the best recovery performance. Finally, the creep compliance master curve of CRM between 10-2 to 109 domain can be obtained by horizontally shifting the creep curves at high temperature. And the horizontal shift factors can be gained. Then, the long-term deformation of the elastic trackbed under the dynamic train load can be predicted by using the equivalent conversion loading time from the short-term dynamic creep test results at 25 ℃ and 0.25 MPa.