Enhancement of flexural behaviour of CFRP-strengthened reinforced concrete beams using engineered cementitious composites transition layer

Abstract

This paper aimed to develop and evaluate an efficient strengthening method for reinforced concrete beams, based on engineered cementitious composites (ECC) to be applied as a transition layer prior to the application of the carbon fibre-reinforced polymer (CFRP) strengthening sheet. The role of the proposed transition layer is to control the cracking of concrete and detain or even avoid premature de-bonding of the strengthening CFRP sheets. As the ability of the transition layer to exhibit a strain hardening behaviour is mainly dependent on the used fibre volumetric ratio, three ECC mixes with three different polypropylene fibre volumetric ratios were used (fibre volumetric ratio of 0.5%, 1% and 1.5%). The experimental results showed that while the used CFRP strengthening sheet can increase the ultimate load by about 28.8% compared with the control un-strengthened beam, this increase can reach about 48.5% by applying the same CFRP sheet to the proposed ECC transition layer that contains a fibre volumetric ratio of 1.5%. Moreover, this layer integrated with the mention ratio of the fibre content enabled the CFRP sheet to be in a complete contact with the strengthened beam without any de-bonding up the rupture of the CFRP sheet at failure.