Strengthening reinforced concrete beams weak in shear using in-house made HPFRC plates

Abstract

HPFRC (High-Performance-Fiber-Reinforced Concrete) is a new concrete technology which showed many impressive results and has been recently used in the construction industry due to many advantages in terms of performance, durability, and mechanical properties. In this study, the main objective was to investigate the effect of HPFRC plates on strengthening the shear properties of reinforced concrete (RC) beams. After conducting various experiments, an ultimate mix was reached consisting of cement, course and find sand, silica fume, superplasticizer, and 1.5% steel fibers per mass of HPFRC mortar. This mix showed an impressive result where a compressive strength of 110 MPa was attained in 28 days. Consequently, a beam with a length of 3m, a width of 0.15m, and a depth of 0.3m was prepared with weak shear reinforcement. The strengthening process consisted of four discontinuous side plates with length of 0.90m, width of 0.3m, and thickness 0.02m bonded on each side of the beam, and one bottom plate with length of 2.7m, width 0.15m, and thickness 0.02m, bonded to the beam that is weak in shear, using epoxy adhesive. A control beam, strong in both shear and flexure with similar dimensions was also cast for comparison. Both beams were tested under two-point load. The strengthened beam (with HPFRC plates) displayed higher shear load capacity and less deflection compared to the conventional NC beam.