Effect of Embedded Length and Bar Diameter of Reinforcement on Bond Strength Behavior of High Strength Concrete Subjected to Elevated Temperatures

Abstract

In case of accidental fire, sabotages reinforced concrete structures get exposed to elevated temperatures, which results in deterioration of its mechanical strength. The deterioration in concrete is due to, its inhomogeneous volume change of concrete ingredients, generation of vapour pressure and decomposition of cement hydration products. Hence, it is significant to study the bond strength between concrete and reinforcing steel.  In the present investigation a study has been carried out on bond strength between high strength concrete and reinforcing steel subjected to elevated temperatures. In order to find the variation in bond strength, various parameters were considered such as bar diameters, embedded length and different temperature levels with 1 hr retention period.  In this investigation 12 mm, 16 mm and 20 mm diameter with two different embedded lengths 150 mm and 300 mm were adopted.  Specimens were exposed to three different temperature levels 200°C, 400°C, 600°C with retention period of 1hr. The experimental results concludes that, under elevated temperatures, embedded length does not contribute more to change in bond strength, but bar diameter and temperature plays important role in change in bond strength and, which is also associated with statistical analysis. From experimental study an empirical formula is proposed to predict the bond strength by considering elevated temperatures, bar diameter and embedded length.

Keywords: Bond strength, Bar diameter, Embedded length, Elevated Temperatures