Shear behaviour of 0.6 % and 0.7 % steel fibre reinforced concrete beams without stirrups

Abstract

Concrete is a brittle material and respectively weak in tensile strength and tensile strain. Concrete technology is applied at which concrete is reinforced with steel fibre, as known as steel fibre reinforced concrete (SFRC) to produce a versatile structural material to exhibit superior strength properties in terms of ductility, fracture energy, toughness, strength and durability. The introduction of short, discontinuous and randomly oriented steel fibres into conventional concrete mixes possesses a strong bond with the concrete matrix with high elastic modulus. The goal of this study is to create a standard foresight in determining the potentiality of steel fibre as secondary shear reinforcement to partially or fully replace shear stirrups in conventional concrete. For this purpose, the series of SFRC beam specimens without stirrups which have the same concrete mixing ratios were produced with the inclusion of 0.6 % and 0.7 % steel fibre by volume fractions and compared with conventional normal weight reinforced concrete (NWRC) beam with stirrups. After the beam specimens had attained the target concrete characteristic strength of C25/30, four-point bending test was conducted to investigate the shear behaviour of reinforced concrete beams. The structural performance of shear beams was evaluated in the response of load-deflection, load-steel strain, crack patterns and failure modes. Test results indicated that with incorporation of steel fibres, the compressive strength and splitting tensile strength were improved, ultimate shear strength was improved up to 36 % at addition of 0.7 % steel fibre content, but water absorption was reduced. Besides, NWRC beam with stirrup increased 43 % in ultimate shear strength which possessed better performance in ductility.