Strengthening of reinforced concrete members using high-performance concrete (HPC) and fiber reinforced plastic (FRP)

Abstract

Strengthening of concrete structures has become very important, not only for retrofitting deteriorated structures, but also for strengthening new concrete structural members to be able to perform better under service loads. The performance of strengthening techniques using High-Performance Concrete (HPC), as well as Fiber-Reinforced Concrete (FRP) has been extensively investigated by many researchers. In this study, strengthening normal concrete (NC) beams using High-Performance Concrete (HPC) plates on the sides and at the bottom of the beam and fiber-reinforced polymer (FRP) wraps at the bottom along with (HPC) plates on the sides was studied. For that purpose, two different types of beams were prepared; the first type with weak shear and bending reinforcements and the second type with strong shear and bending reinforcements. For each beam type, six beams, in which one is non-strengthened, were cast and strengthened differently. The HPC plates were composed of a mix containing 1.5% steel fibers per mass of HPC mortar. The FRP wraps consisted of stitched, unidirectional, carbon and glass fiber fabrics, and impregnating resins. The strengthening technique was done by bonding either the HPC plates or FRP wraps by an epoxy adhesive. The beams were tested under a two-point loading test. The results showed that all strengthened beams were stiffer and stronger than the non-strengthened beams, while the failure mode of the beams shifted from shear failure to flexural failure with the addition of either HPC plates on the sides and at the bottom or FRP wraps at the bottom with HPC on the sides. In addition, a comparison between the HPC plates and the FRP wraps at the bottom of the beam was provided to present the best results. The experimental results showed that both configurations resulted in a high load capacity, however the FRP failed in a brittle behavior. In addition, the continuous side plates performed better than the discontinuous side plates in terms of shear strengthening, load capacity, deflection, and crack pattern. Therefore, it can be concluded that the application of the HPC plates on the sides and at the bottom improved the mechanical properties and behavior of the beam, as well as increasing the load capacity with less deflection. For further studies, it is recommended to study the effect of HPC on largescale beam to confirm its consistency and generalize HPC plates as an effective strengthening method for RC beams.