Jagdish Chand, S.M. Gupta and Babita Saini Department of Civil Engineering, National Institute of Technology, Kurukshetra – 136119, Haryana, India
Introduction
Concrete as a construction material is used on large scale all over the world in view of its compressive strength, structural stability, high mouldabilty and economic considerations. Also, it is very strong in compression; but, its tensile strength is comparatively very weak [1]. Ordinary conventional concrete has been replaced with high strength concrete due to improvement in physical properties in the construction industry from the last few decades. The development of new water reducing admixtures and the mineral admixtures is making it possible to produce more reliable high strength concretes in the recent years [2]. The direct compression test method is used to determine its compressive strength. However, there is no direct method to determine the tensile and/or shear strength concrete. Therefore, attempts have been made to predict the indirect split tensile strength of concrete by casting and testing cylinders and prisms [1, 3]. Concrete being a non-homogeneous, heterogeneous material and have non-linearity in its material response [4, 5]. As a result of this, it is not feasible to apply a shearing action (direct shearing force) in a plane, as a common practice is done in case of metals. Steel bars generally provided along a direction perpendicular to shearing force, act to resist shearing force. The shear resistance due to these longitudinal steel bars is commonly referred as dowel effect [5, 6, 7]. However, incorporation of such steel bars does not contribute much in the tensile strength of concrete [8, 9, 10]. A small amounts of fibers introduced in concrete may improve the shear properties of high strength concrete. The concept of introducing the natural fibers in brittle building materials is not new and had been used from ancient civilizations to reinforce deteriorating adobe bricks [5, 6, 11, 12, 13]. Although different types of natural, synthetic and steel fibers are available; but, more research has been performed using steel fiber in concrete and further investigations about material properties and behavior are still required to be studied. The introduction of steel fibers in concrete significantly improves its ductility and thereby improves
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