Bond Performance of Seamless Steel Pipe Grouting Sleeves under Large-Deformation Repeated Tension and Compression after High Temperature

Grouting sleeves are widely used in the field of assembled construction. The present study aims to investigate the reliability of grouting sleeves under large-deformation repeated tension and compression after high temperature, considering the influences of steel bar diameter, the cooling method, and the protective layer. Through experimentation on 28 test pieces, we analyzed the bonding performance of the test pieces at different high temperatures. The results indicate that within the temperature range of 20-800 degrees C, the bond performance of the test pieces declines by no more than 9.8%. However, upon reaching a temperature of 1000 degrees C, the bond performance of the test pieces decreases by over 33.7%, with the compressive strength of the grout material reduced to only 27.50% of that kept at 20 degrees C. Employing larger-diameter steel bars is advantageous for maintaining the bond performance of the test pieces. Natural cooling shows relatively good bond performance, although its influence is not significant. Furthermore, the protective layer effectively attenuates the heating rate of the test pieces, thus safeguarding their bond performance. Scanning electron microscopy (SEM) analysis reveals that the decomposition of C-H and C-S-H phases is the primary cause of high-temperature degradation of the grouting material. Finally, a recommendation for the correlation coefficient (k) between the average bond strength and the compressive strength of the grout material is proposed, with a suggested value of k <= 2.58.