SHEAR STRENGTH OF FIBRE BASED CONCRETE

Abstract

Steel fiber reinforced concrete is increasingly being used day by day as a structural material. Although considerable research has been done on the shear strength of Fiber Based Concrete (FBC), the debate as to the effect of major variables on the cracking and ultimate shear strength has yet to be unequivocally established. The present work is an experimental investigation on the shear performance of FBC beam elements and various structural properties of FBC viz. compressive strength, modulus of rupture, flexural toughness. In this study, four different types of steel fibers with different aspect ratio (1/d=33.5, 36, 45, 80) were used in volume fractions of 0.5, 1.0, 1.5, and 2.0 percent. Although the rate of increase in compressive strength of concrete was not found convincing, through the addition of fibers, yet the increase in modulus of rupture was found to be significantly large, nearly 40% for fiber addition of 1%. The drawn load deformation response (stress-strain profile) for fiber based concrete clearly indicate that sufficient amount of ductility induced in brittle concrete through the addition of fibers rendering the material tough from seismic point of view. The important aspect for the better performance of fibre based concrete (FBC) is the number of homogeneously distributed fibres available per unit volume of concrete. Also it was found that increase cracking strength, ultimate shear strength and improved ductility largely depend on the volume fraction of fibres The results of good number of FBC beam elements which were tested to investigate the influence of steel fibers on the shear and deformation characteristics have been presented. Variables considered in the present study include concrete strength, fiber content, tensile reinforcement ratio and aspect ratio. It was found that increased cracking strength, ultimate shear strength and improved ductility largely depend on the volume fraction of fibers. The beam elements with reinforcement ratio of 1.5% which failed in shear; exhibited shear-flexure failure at a fiber content of 1%. Nevertheless, the fiber based beams which failed in Flexure and Flexure-Shear mode exhibit sufficient ductility. The results were compared with Indian, British and American Codes and showed good agreement. The results of Indian Code were found to be much conservative side when compared with British and American Code and experimental results.