Experimental Evaluation of Bond Behavior between Corroded Reinforcing Bars and Concrete under Elevated Temperatures

The bond performance of corroded reinforced concrete (RC) subjected to fire has a significant influence on evaluating the structural load-bearing capacity and early warning for structure collapse. However, the bond deterioration mechanism of corroded RC subjected to fire has not been sufficiently studied. Therefore, in this study, the bond behavior between corroded reinforcement and concrete at elevated temperatures was systematically investigated by testing 76 corroded specimens obtained by the accelerated corrosion method. Eccentric pull-out tests were performed immediately when the temperature at the interface of the reinforcement and concrete reached the target values. The main parameters include the degree of corrosion (i.e., 0%, 2%, 5%, 10%, and 20%), concrete cover thickness (20, 30, and 40 mm), and temperature (20 degrees C, 100 degrees C, 200 degrees C, 400 degrees C, 500 degrees C, 600 degrees C, and 800 degrees C). The test results indicated that when exposed to temperatures below 400 degrees C, the bond strength at elevated temperatures is less than that after natural cooling. The bond strength changed minimally at elevated temperatures between 200 degrees C and 400 degrees C, while a significant reduction was observed after natural cooling. Moreover, the bond strength increased by 8.7% at less than 3.4% corrosion degree. However, severe corrosion (with a corrosion degree exceeding 13.2%) and high temperature (exceeding 500 degrees C) decreased the bond strength by 16.3% and 29.6%, respectively. In addition, methods for calculating the bond strength and residual bond strength based on the deterioration of concrete compressive strength at elevated temperatures are proposed.