Experimental Study of High-Temperature Exposure Effect on Reinforcement-Concrete Bond in Corrosion-Damaged Reinforced Concrete

The object of this study is the bond between reinforcement and concrete after exposure to high temperatures and corrosion, which is critical for assessing the durability of reinforced concrete structures. The analysis of scientific sources revealed that at temperatures above 300°C, the bond deteriorates due to thermal expansion of the reinforcement, degradation of the cement matrix, and crack formation. Simultaneously, corrosion reduces adhesion and weakens mechanical interlocking, accelerating concrete deterioration. However, the combined effect of these factors remains insufficiently studied, and the existing bond models do not fully account for their simultaneous impact. In this experiment, concrete specimens with A500C reinforcement were subjected to electrochemical corrosion and heated to 400°C. Pull-out tests revealed a significant reduction in bond strength, attributed to the destruction of the adhesive layer and changes in the interaction mechanism: in unheated specimens, the bond was ensured by plastic deformations of concrete, whereas in heated specimens, it was maintained by friction against corrosion products. Comparison with previous studies on the influence of temperature, reinforcement types, and heating rates confirmed the consistency of the results and clarified the role of pre-existing corrosion. The obtained experimental data not only validates the existing studies, but also extends them by incorporating the effect of pre-corrosion, which was previously considered in a limited scope. The findings can be used to predict the consequences of thermal exposure, assess the residual strength of structures, and develop restoration methods.