A series of pull-out tests were conducted to examine the bond deterioration of epoxy resins at elevated temperatures through the relationship between the critical temperature and bond stress. The steel rebars investigated were deformed bars with varying diameters of 12 mm, 16 mm, 20 mm and 25 mm. Two different types of epoxy resins were used. The test results show that the critical temperature for both types of epoxy resins tends to decrease with the increasing bond stress. In addition, the critical temperature is significantly lower for steel rebar with larger diameters. Meanwhile, the effect from varying types of epoxy resins on the bond characteristics is negligible. In order to illustrate the effect of rebar size, a mechanical model for the adhesive bonding stress between steel rebar and concrete interface at elevated temperatures is presented. The model provides good prediction of the bond stress at failure temperature.