Retrofitting of different types of reinforced concrete beams after exposed to elevated temperature

Abstract

The development of the concrete industry has facilitated the use of nonconventional concrete types, such as high-strength concrete (HSC) and self-compacting concrete (SCC). Normal concrete (NC) beams experience a significant reduction in their strength after fire exposure. An experimental program is designed to investigate the effect of different levels of temperature on the most common concrete types and the effect of different retrofitting techniques to restore the capacity of reinforced concrete beams. Thirty-one beams were casted using NC, SCC, and HSC. Twenty-eight beams were subjected to temperatures of 400 °C and 600 °C for 60 min and 120 min to evaluate the beam behaviour under indirect fire conditions. Carbon fibre reinforced polymer (CFRP) laminates, bonded steel plates, and concrete jacketing have been used for beam capacity retrofitting. The exposure time at a high temperature level had a significant effect on the behaviour of the different beams, especially those with NC, which underwent a dramatic reduction in strength after being subjected to 600 °C for 2 h. The SCC beams had an acceptable behaviour under elevated temperature conditions. All the retrofitting techniques had a positive effect on SCC and HSC beams, but the bonded steel plate and CFRP techniques did not produce a noticeable effect on NC at 600 °C. The reinforced concrete jacket had a satisfactory effect in the drastically deteriorated beams.