Interpretation of Modulus of Elasticity of Normal Strength Concrete with Hook-end Steel Fibres

Abstract

The brittleness characteristic of a plain concrete or the concrete embedded with longitudinal ferrous reinforcements possess a low tensile strength, limited ductility and little resistance in cracking. This inherent deficit in the property of concrete can be overcome by the addition of multidirectional and closely spaced short discontinuous steel fibres distributed randomly. Short, discrete steel fibres provide discontinuous three-dimensional reinforcement that picks up load and transfer stresses at micro-crack level. This fibre reinforcement provides tensile capacity and crack control to the concrete section prior to the establishment of visible macro-cracks thereby promoting ductility or toughness. Addition of fibres plays an important role in the improvement of the mechanical properties of concrete like increase in elastic modulus, decrease in brittleness, increases tensile strength, energy absorption and control of crack initiation and propagation. In the present study, the effect of steel fibres on the modulus of elasticity of Normal Strength Concrete (NSC) is evaluated. Hook-end steel fibres of diameter 0.75mm and with an aspect ratio of 80 were used at different fibre volume fractions of 0%, 0.5%,1.0% and 1.5%.Cylinder specimens of standard size 150mm diameter x 300mm height were prepared and then subjected to uniaxial compression. From the test results, it was shown that Steel Fibre Reinforced Concrete (SFRC) specimens exhibited ductile behavior after reaching their compressive strength. Further, it was shown that the compressive strength generally increased along with an increased in fibre volumetric ratio, while the elastic modulus decreased.