Time-temperature analysis of bond strength of a rebar after fire exposure

The extent of damage to a steel-reinforced concrete structure due to fire exposure must be evaluated before deciding whether to reuse, reinforce, or abandon the structure. Understanding the long-term effects of high temperature on steel-reinforced concrete structures is also important for predicting the service life of a structure in a high-temperature environment. These effects include changes in strength, stiffness, toughness, bond strength of the rebar, and so on. The change in the bond strength of rebars is studied herein. The experimental results of postfiring pullout tests show a substantial decrease in bond strength if the exposure temperature reaches 200 degreesC or higher. The current investigation proposes a procedure, based on a single function, to calculate changes in bond strength for predicting residual bond strength of a rebar due to exposure to constant or fluctuating high temperatures. This forecasting method is termed temperature-time analysis and offers excellent agreement with the experimental results. (C) 2003 Elsevier Ltd. All rights reserved.