Flexural behaviour of MRBC beams (multi-reinforcing bars concrete beams), promoting the use of FRHPC

High performance concrete reinforced by short metallic fibers has been recently developed. These materials are of particular interest for civil engineering thanks to their high compression performance and to their enhanced durability. The addition of short metallic fibers provides the opportunity to obtain a more ductile material with more resistance to tension. Nevertheless, the use of reinforcement is still necessary for structural applications [1]. This paper presents results obtained on SFRHP concrete beams using mixed steel–CFRP rebar. Five beams with steel rebar or mixed CFRP–steel reinforcement were designed according to Eurocode 2. The goal is to optimize the reinforced concrete (RC) beam design by combining different reinforcement types in order to use the fiber reinforced HPC most efficiently. The first beam specimen uses a non-fibrous HPC and constitutes a reference for comparison. The tests carried out upon an FRHPC beam and reinforced by steel reinforcing bars allow the assessment of the short fiber’s effect against the bending and the shearing stresses. It is shown that the presence of short metallic fibers in the concrete does in fact contribute to the equilibrium of the beam. The sum of the internal moments in the tensile zone is increased by 10%. For the last three beams, the effect of incorporating carbon fiber reinforced polymer rebar mixed with usual steel reinforcement is studied. It is shown that beams using mixed CFRP–steel rebar are able to achieve a bending stiffness comparable to the beams reinforced by traditional steel reinforcement (in the elastic stage). A 50% increase in the failure load is observed.