Effect of steel fibres on the tensile behaviour of self-consolidating reinforced concrete blocks

This paper reports the recent findings of an experimental investigation on the influence of steel fibres in RC blocks under quasi static direct tensile loading. Structural blocks were designed with rebar reinforcement ratios of 0.40, 0.63 and 1.00%. A structural direct tensile testing system was developed at the COPPE laboratories resulting in a state-of-the-art in house apparatus. The RC blocks were reinforced with 1.25% volume fraction of steel fibres and without any type of fibre reinforcement and then tested until a strain level of approximately 0.0015mm/mm. The results show that the steel fibres improved the stress transfer efficiency between the rebars and the concrete matrix. By partially replacing the rebars by steel fibres the ductility of the concrete block was augmented and the post-crack stiffness increased. These results and possible mechanisms are discussed on the basis of the observed crack patterns, deformation measured on the steel rebars, computed deformation of the concrete matrix and on the overall mechanical behaviour of the composite concrete block.