High-temperature effects on bond behaviour between concrete and corrosion resistant steel reinforcements

The construction industry's response to the rising demand for robust and enduring structures is evident in the growing emphasis on protective measures to enhance the durability of concrete structures. Application of these protection methods to reinforcing bars may influence the bond behaviour between concrete and steel reinforcements. Despite several studies have looked into this topic at room temperature, there is a big research gap concerning the bond behaviour between concrete and steel reinforcements protected from corrosion after exposure to high temperatures, such as those experienced in fires. In this study, pull-out tests were conducted on concrete specimens featuring unprotected, cold-galvanised, hot-dip galvanised, and stainless-steel bars after exposure to temperatures reaching up to 600 degrees C. Two rebar diameters were studied, 12 and 16 mm, for all the rebars. The results indicate that the use of corrosion protection methods for steel bars does not lead to catastrophic failures in terms of bond strength after exposure to high temperatures. The reduction in bond strength obtained with increasing temperature follows a similar trend as the reduction in concrete compressive strength at elevated temperatures, as stipulated in existing codes. Furthermore, the study proposes a modification of the existing predictive model from Model Code 2010 for the maximum bond stress between concrete and reinforcement, in order to incorporate the exposure to elevated temperatures, considering the protection methods or rebar materials studied.