Comparative Experimental Study of the Flexural Behaviour of UHP-SFRC and ECC Beams Reinforced with Smooth Bars

Research in seismic engineering continues to investigate the mechanical behaviour of various emerging and novel materials for application in a wide range of structural elements. This includes promising materials such as Superelastic Shape Memory Alloys (SE-SMAs) due to their self-centering properties, and high-performance concretes such as Ultra-High Performance Steel Fibre Reinforced Concrete (UHP-SFRC) and Engineered Cementitious Composites (ECC) due to their enhanced tensile deformation characteristics. Unlike traditional deformed reinforcing bars, the SMAs used in several studies for seismic applications are formed into smooth bars. This type of surface leads to reduced bond strength between the SMA and the surrounding concreting material used in a structural element. ECC and UHP-SFRC have demonstrated the ability to increase bond strength due to the presence of fibres in the matrix. This paper aims to quantify the effect of ECC and UHP-FRC on the flexural behaviour of beams reinforced with smooth bars based on increased bond capacity relative to beams with normal strength concrete. Two sets of beams consisting of ECC or UHP-SFRC reinforced with smooth bars were subjected to four-point loading. All beams were designed to ensure that flexural failure would occur in the constant moment region. Included in the experimental results was a set of control beams consisting of the same reinforcement but with normal strength concrete. The results demonstrated that the beams with ECC and UHP-SFRC provided improved flexural strength across all beams with deformed and smooth reinforcement relative to beams casted with normal strength concrete. In all tests, beams with UHP-SFRC provided higher flexural strength capacity than beams with ECC.