Developing Rules of Adhesive Properties and Mechanism of Ballastless-Track Sealants in Shear-Fatigue Loading

There is no method for evaluating the shear-fatigue resistance of sealants installed in the supporting layer of ballastless track, and the degradation mechanism of sealants under shear-fatigue loading has not been studied systemically. This study develops a shear-fatigue loading test method, and the adhesive properties of sealants are researched during shear-fatigue loading. The functional-group character at the failure interface is analyzed using infrared spectroscopy, and then the correlation between macromechanical behavior and the micromechanism is discussed. Results show that both maximum loads and failure displacements have a downward fluctuating trend during shear-fatigue loading, and sealants with lower hard-phase content present better shear-fatigue resistance. No new chemical bond forms in sealants, but more soft phases fuse into hard phases, which decreases the microphase separation degree of sealants. The developing rules for the hydrogen bonding index identify a trend similar to that of the mechanical behavior of sealants caused by the orientation of amorphous phases. The hydrogen bonding index degradation of higher R value sealants is deemed more significant, which agrees well with the results of the direct tension test.