Experimental Investigation on Bond Strength of Concrete and Steel Bar of Conventional Concrete at Elevated Temperatures

An experimental investigation is done on bond strength of reinforcing bar and surrounding concrete at elevated temperatures. The conventional mix M25 is used and three different types of steel bars of 20 mm diameter are used. A total of 9 pull out specimens are prepared; 3 using plain polished bars, 3 using plain unpolished bars and 3 using deformed bars. Embedment of steel bar inside the concrete specimen is done. The pull out specimens are subjected to room temperature and two different elevated temperatures 100ºC and 300ºC. Comparisons are done between the different steel bars and temperatures. The results indicated that the pull out specimen with deformed bars at room temperature had the highest bond strength compared to the other bars with different temperatures. The plain bars have shown the least bond strength due to the chemical adhesion and friction. When temperature is taken into concern, there was decrease in bond strength for 300ºC compared to room temperature. In the deformed bars, there was a decrease in 14.94 % when subjected to 300ºC. In polished mild steel bars, when subjected to 300ºC decrease in 22.46 % than room temperature. Similarly, in unpolished mild steel bars there was a decrease of 40.86 %.