Experimental study on the shear behavior of RC beams reinforced by natural composite materials (flax fibers)

The context of this study is the shear strengthening analysis of a concrete beam using a new natural material. This paper presents the experimental results of the shear reinforcement of concrete beams with a flax fiber reinforced polymer (FFRP) using the External Bonding method (EB) and the Near Surface Mounted method (NSM). A total of 16 beams were tested with three point bending tests. The beams had rectangular sections and a 2-meter span and a T sections with a 2.5 m span. The following parameters were investigated: (i) the percentage of flax reinforcement (continuous vs non continuous), (ii) the percentage of transversal steel (stirrups), (iii) the method of reinforcement (EB vs NSM), (iv) and the interaction between the FFRP and the stirrups. The results obtained showed that the ultimate load increased by 10% to 35% for these reinforced beams; however, this type of reinforcement did not contribute to a modification of the type of failure or the behavior of post failure. The results also showed that the NSM method is more efficient than the EB method. In addition, the presence of transversal reinforcement reduces the contribution of flax fibers in the shear resistance of the beam. Finally, the experimental results obtained are compared succefully to different design code equations.