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A. Namdar et alii, Frattura ed Integrità Strutturale, 26 (2013) 22-30 ; DOI: 10.3221/IGF-ESIS.26.03 22 An experimental study on flexural strength enhancement of concrete by means of small steel fibers Abdoullah Namdar, Ideris Bin Zakaria, Azimah Bt Hazeli, Sayed Javid Azimi, Abdul Syukor Bin Abd. Razak Department of Civil Engineering & Earth Resources, Universiti of Malaysia Pahang, Malaysia ab_namdar@yahoo.com G. S. Gopalakrishna Department of Earth Science, University of Mysore, India A BSTRACT . Cost effective improvement of the mechanical performances of structural materials is an important goal in construction industry. To improve the flexural strength of plain concrete so as to reduce construction costs, the addition of fibers to the concrete mixture can be adopted. The addition of small steel fibers with different lengths and proportion have experimentally been analyzed in terms of concrete flexural strength enhancement. The main objectives of the present study are related to the evaluation of the influence of steel fibers design on the increase of concrete flexural characteristics and on the mode of failure. Two types of beams have been investigated. The force level, deflection and time to failure of beams have been measured. The shear crack, flexural crack and intermediate shear-flexural crack have been studied. The steel fiber content controlled crack morphology. Flexural strength and time to failure of fiber reinforce concrete could be further enhanced if, instead of smooth steel fibers, corrugated fibers were used. K EYWORDS . Steel fiber; Flexural strength; Corrugated steel fiber; Flexibility of beam; Shear crack; Flexural crack. I NTRODUCTION he fiber reinforcement concrete mix design helps to construct high quality of concrete structure. To improve concrete strength, effect of fiber distribution on flexural strength of ultra-high strength concrete has been investigated. The ultimate flexural strength and time to first crack have been affected [1]. The placing methods control fiber distribution and mechanical performance of short-fiber reinforced concrete [2, 3]. The flexural behavior include cracking, failure pattern, deflection, ductility, and flexural strength have been studied. A prediction model for the flexural strength and deflection of ultra-high strength concrete beams under bending conditions has been proposed [4]. There is an analytical solution for calculation of flexural strength of strengthened composite beams. And experimental results from literature have been employed to validate results of both the analytical and finite element method [5]. A design method has been reported on ultimate strength criteria for small steel fiber reinforced concrete (SFRC) slabs. The slabs under flexure, with longer fibers and higher fiber content provide higher energy absorption [6-7]. The splitting tensile and flexural strengths have largely been improved with increase fiber volume [8]. The ductility of concrete with synthetic fibers has been investigated for analysis flexural stress-deflection [9]. The objectives of this research work are, to investigate effect of small steel fibers on flexural strength of small beam. The length and proportion of steel fibers have been investigated. The deflection, time of stability and crack morphology of the concrete beams have been discussed. T