Issue 42

A. Jadidi et alii, Frattura ed Integrità Strutturale, 42 (2017) 249-262; DOI: 10.3221/IGF-ESIS.42.27 249 Experimental evaluation of steel fiber effect on mechanical properties of steel fiber-reinforced cement matrix Ali Jadidi, Milad Amiri , Ehsanollah Zeighami Department of Civil Engineering, University of Islamic Azad, Arak, Iran alijadidi1369@gmail.com, Ehsanollahzeighami@gmail.com , Miladamiri1374@gmail.com A BSTRACT . This paper investigates the possibility of combining steel fibers with different weight percentages along with their functions in increasing compressive strength, indirect tensile strength and bending strength. In this study, two types of steel fibers, hooked and crimped, have been employed in the preparation of samples. These fibers have a length to diameter ratio of 30 mm and 50 mm (L/D=30 and L/D=50). Further, the combination of these fibers caused a reduction in concrete flow and reduced its efficiency. The combination of these fibers caused considerable increase of concrete bending strength compared to fibreless and single-fiber type concretes. In this research, tensile strength and bending strength of samples with 1.5%, 2% and 2.5% fibers were investigated in which the tensile strength and bending strength of all samples increased. However, there were very considerable increases in tensile strength and bending strength of samples made with hybrid crimped fibers. The results indicated that steel fibers did not have much impact on concrete compressive strength . K EYWORDS . Mechanical properties; Fiber concrete; Hybrid concrete; Steel fibers; Indirect tensile test. Citation: Jadidi, A., Zieghami, E., Amiri, M., Experimental evaluation of Steel Fiber Effect on Mechanical properties of steel fiber- reinforced cement matrix, Frattura ed Integrità Strutturale, 42 (2017) 249-262. Received: 20.05.2017 Accepted: 13.08.2017 Published: 01.10.2017 Copyright: © 2017 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION oncrete, considering its structure, has advantages and disadvantages among which tensile strength and low bending strength versus its high compressive strength can be mentioned. This accounts for the brittleness of concrete and is considered a major cause for the sudden failure and destruction of concrete structures. Since mid- eighteenth century, steel round bars were used to improve the brittle behavior of concrete under tensile forces. However, in many cases, tensile forces could not precisely be spotted, and distribution of steel round bars all throughout the concrete is not possible. Therefore, nowadays, the use of various fibers is one of the solutions to improve concrete brittle behavior and reduce its permeability [ 1 ] . In 1960s, Baston and Ramualdi made the first attempt to reinforce concrete using steel fibers in the United States. Since then, countless researches and industrial applications have been carried out on steel fiber reinforced concrete [ 2 ] . Qureshi et al., investigated the properties of high strength concrete by adding steel fibers. Test results revealed adding steel fibers increases tensile strength in a linear manner, with the increase rate higher in C