Bond performance of grouted tendons at elevated temperatures

Abstract

The bonding between the tendons and grout is crucial to the performance of bonded post-tensioned concrete structures. To study the bond performance of grouted tendons at elevated temperatures, pull-out tests were conducted on specimens, each of which comprising either a mono- or multi-strand tendon located centrally within a grouted duct inside a concrete cylinder, at test temperatures ranging from 20°C to 600°C. Results show that the bond strength deteriorates with the rise in temperature and the degradation of bond strength is more severe than that of the other mechanical properties of materials. Three types of failure mode of the specimens were observed, i.e. pull-out, partial splitting and through splitting. Using a smaller duct can improve the bond strength when the specimens fail in the pull-out mode. However, the influence of the strength of outer concrete is insignificant. Based on the distinct bond behaviour of different failure modes, a bond-slip model was proposed by regression of test results.