Time Dependent Properties of Steel Fibre Reinforced Concrete

Abstract

Plain cement concrete is one of the most widely used construction materials as it is with known properties and can be cast to any form and shape. The relatively low tensile strength of plain cement concrete is normally considered as an unavoidable deficiency of the material. Microcracks are inherently present in the material which further propagate due to loading,eventually leading to brittle fracture. The microcracks appear during volumetric and microstructural changes at the initial stages of setting and hardening. A discontinuous heterogeneous system thus exist even before the concrete is subjected to external load. On the application of load, initial microcracks start developing at about 30 to 40 percent of the ultimate compressive strength and subsequent loading leads to uncontrolled growth of cracks. This phenomenon results in the low fracture toughness and limited resistance to impact and shock loading. newlineTo overcome the above deficiencies, reinforcing and pre-stressing of concrete structures have been invariably used. newlineThe major limitation of the conventionally reinforced concrete is that the steel reinforcement in the tension zone does not improve the tensile properties of concrete. newlineConventional reinforced concrete is not a two phase material in the true sense of the word. The exist*nce of one phase i.e., steel or concrete does not improve the basic strength properties of the other phase and consequently overall performance of the composite material is dictated by the individual performance of the concrete phase and the steel phase. newlineThis inadequacy led to the innovation of reinforcing the weak matrix with a stiff and strong material to produce a composite of superior properties. Steel fibre reinforced concrete is one of the materials which overcomes a number of shortcomings of plain concrete. newlineFibrous concrete is a composite material of concrete matrix with an evenly distributed closely spaced steel fibres.