Study on the interface damage of CRTS II track slab under high- and low-temperature cycles based on acoustic emission

China Railway Track System (CRTS) II slab tracks have been widely used in high-speed railway construction. Interface debonding between the track slab and cement-emulsified asphalt (CA) mortar is one of the typical diseases of the CRTS II slab tracks. Properly evaluating the interfacial strength of the track slab and CA mortar under high-and low-temperature cycles is crucial for optimizing the repair in engineering practices. In this study, the track slab and CA mortar (TSCAM) composite specimens were prepared for high-low temperature cycle (HLTC) tests. Then, the shear and tensile tests were carried out to study the interlayer bonding properties of TSCAM under different HLTCs. In addition, the acoustic emission (AE) technique was employed to monitor the signals generated in the specimen during the tests. Furthermore, the AE parameters were analyzed, including ringing counts, energy, b-value and amplitude-frequency. The results show that the number of HLTCs signifi-cantly contributed to the deterioration of the interface bond strength between the track slab and the CA mortar. The interface normal bond strength showed a higher decrease than the tangential bond strength with the increase of HLTCs. In addition, the relationships of the shear and tensile bond strength of the TSCAM composite specimen with HLTC were deduced. The tangential and normal bond strength degradation properties of the composite were well fitted by the function of quadratic polynomial and power exponents, respectively. The AE activities of the composite specimens in the shear and tensile tests were gradually reduced with increased HLTC. The AE signals were the strongest when the specimen failed along the interface. Furthermore, the intensity of AE events during the shear test was higher than that during the tensile test under the same HLTC. The overall b-values of the shear and tensile specimens without HLTC were the largest and did not change significantly with the increase of HLTC. The amplitude range of the peak frequency gradually decreased as the HLTC increased. The amplitude and peak frequency of the tensile test was smaller than that of the shear test under the same HLTC. This indicates that the AE technique can monitor the interface damage evolution pattern of the TSCAM composite specimen throughout the tests.