Experimental Study on Bond Performances of Track Slab and Mortar Based on DIC Technology

In order to guarantee the normal long-time service performance of CRST II slab track, it is necessary to study the interface parameters between track slab and CA mortar layer of CRTS II slab track. Thus the splitting and shearing model test of concrete and mortar bonded composite specimens were conducted. Based on the Digital Image Correlation (DIC) technology, the stress-strain relationship and cohesion model parameters were obtained from the interface displacement and distribution of strain. The results showed that: The displacement and the strain field distribution of the composite specimens as well as the whole interlaminar cracking process of initiation, propagation and failure can be well described with DIC. The bond failure between the track slab and the CA mortar layer is part of the brittle failure, and the normal and tangent interface tension-displacements are both bilinear. The shear strength between the track slab and the CA mortar layer is 1.82 MPa with the peak strain of 2.49 x 10(-4) and the secant modulus of 7.30 x 10(3) MPa; While the shear strength is 2.40 MPa with the peak strain of 6.17 x 10(-3) and the secant modulus of 3.89 x 10(2) MPa. When the shear strain is about 7.5x10(-4), the shear stress-strain curve tends to remain stable. At this point, the shear strain is 0.12 times of the peak strain. Parameters of the cohesive zone model between the track slab and the CA mortar layer are suggested as follows: the normal cohesive strength is 1.792 MPa with the interface stiffness of 708.485 MPa/mm and the critical fracture energy of 0.0252 mJ/mm(2); the tangential cohesive strength is 0.956 MPa with the interface stiffness of 63.039 MPa/mm and the critical fracture of 0.018 mJ/mm(2).