Improvement of bond behaviour between steel bar and concrete subjected to elevated temperature at early age.

In this paper, the bond behaviour of reinforced concrete exposed to high temperature at early age has been investigated. The influence of temperature, curing age before exposing to high temperature and repair agent on the ultimate bond stress and bond displacement of reinforced concrete are analysed. The ultimate bond stress of specimens decreases with the increase in temperature, while the ultimate bond displacement increases with the increase in temperature. After being subjected to the same temperatures, the ultimate bond stress of the specimen heated at a curing age of 28 d is found to be lower than that of specimens that were heated at curing ages of 3, 7 and 14 d. However, the ultimate bond displacement of the specimen heated at the age of 28 d is larger than that of specimens heated at the ages of 3, 7 and 14 d. The ultimate bond stress of the specimen using a repair agent is greater than the ultimate bond stress of the specimen without using the repair agent. On the contrary, the ultimate bond displacement of the specimen using a repair agent is found to be less than that of the specimen without using a repair agent. [ABSTRACT FROM AUTHOR]