A review of experimental factors influencing bond strength at elevated temperatures

After a fire, engineers must determine if a building should be demolished or repaired based on its condition and ability to support future loads. Evaluating the structure’s strength post-fire is essential. High temperatures can degrade concrete properties—such as compressive and tensile strength, and the bond between re- bar and concrete. These properties are vital for assessing the building’s safety and design. Evaluating bond strength at elevated temperatures is complex, as the heating procedure, heating rate, and cooling process influence the bond after exposure to fire. Although researchers recognize these factors, the extent of their impact remains a topic of debate. After a fire, researchers typically evaluate residual bond strength using pullout and beam tests to assess material deterioration. This measurement is expressed as the ratio of bond strength at high temperatures (ranging from 20 °C to 800 °C) to the bond strength at ambient temperature, which is usually around 20 °C. This paper reviews the literature on bond strength at elevated temperatures, investigating the factors that affect this strength. It discusses the bond-slip curve and the impact of different experimental variables, including the heating procedure, rate and duration, cooling method, rebar properties, specimen characteristics, and the residual bond strength following high-temperature exposure.