GRD Journals- Global Research and Development Journal for Engineering | Volume 4 | Issue 3 | February (2019) ISSN: 2455-5703
Flexural and Flexural Toughness of Fiber Reinforced Concrete- American Standard Specifications Review Ali Jihad Hamad Lecturer Department of Construction Materials Technology Engineering Northern Technical University / Engineering Technical College of Mosul / Iraq
Rami Joseph Aghajan Sldozian PhD Candidate Department of Applied Sciences University of Technology / Baghdad / Iraq
Abstract Fibers used to enhance the brittleness property of steel reinforced concrete and plain concrete, and modify the tensile strength by increasing work of fracture. Thus, the toughness measurements are valuable for assessing the post crack performance of fiber reinforced concrete (FRC). There are many international standard around the world, but this paper are focuses on review the American standard specifications via exclusive ASTM. The review involve the flexural strength testing methods and toughness testing methods for FRC. For flexural strength test, the ASTM C 78 and ASTM C 293 reviewed and compared between both, while for toughness the ASTM C 1018, ASTM C 1609, ASTM C 1399 and ASTM C 1550 reviewed. This paper also describes concisely the method for each testing and considerable advantages of these methods. Beside, abridged some limitation of these methods. All figures have been redrawn with inserted more details to be most obvious and more rich. Keywords- Flexural, Flexural Strength, Toughness, Flexural Toughness, Fiber Reinforced Concrete (FRC) __________________________________________________________________________________________________
I. INTRODUCTION Fiber reinforced concrete (FRC) is define as a concrete having dispersed randomly oriented fibers (ACI 116r) [1]. The addition of fibers to the concrete have wide range of usage due to their evident advantages over ordinary concrete. The function of the use of fibers in concrete is to enhance the mechanical properties of concrete. Fibers used to modify the flexural strengths, toughness, impact resistance, fracture energy, and restrain crack formation. The concrete with fibers as additives used widely in highways, tunnel linings, concrete pipes, reinforced concrete frames, reinforced concrete beam members, shell roof systems, skyscrapers, pre-stressed concrete, light shell constructions, domes and folded plates in recent years [2-5]. Plain concrete (unreinforced concrete) breakdown suddenly when the deflection corresponding to the ultimate flexural strength exceeded, oppositely FRC continues to withstand considerable loads even at deflections significantly in excess of the fracture deflection of the plain concrete [6]. The fractured specimens of FRC exhibits that failure takes place chiefly due to fiber pull-out or debonding. Therefore, FRC specimen does not break immediately after first crack as shown in Figure 1. This has the effect of increasing the work of fracture, which denoted to as toughness and represented by the area under the load-deflection curve [6].
II. FLEXURAL STRENGTH When the flexural strength test is characterize the evaluation of tensile strength of concrete; also, the flexural strength named as a modulus of rupture (MOR) or (MR) [6, 7]. The standard test methods of ASTM C 78 [8] and ASTM C 293 [9] used to determine the flexural strength. A. ASTM C 78 versus ASTM C 293 The standard test method ASTM C 78 [8] achieving simple beam by applying third-point loading (four-point bending) and ASTM C 293 [9] achieving simple beam by applying center-point loading (three-point bending). The specimen for a flexural strength test matching to ASTM C 78 [8] and ASTM C 293 [9] should be confirmed to the dimensions in Figure 2 (a and b), and shows the planning and arrangement for the flexural strength test. The common specimen used is 150×150×500 mm, but used 100×100×500 if the maximum aggregate size is less than 25 mm [6, 7]. In ASTM C 78 [8] the span length (L, distance between the two reactions or supports) of test specimen divided into three third L uniform and should be achieve the of ratio of any third to the depth of the specimen ( / d = 1) shall be equal 1. Beside, in ASTM 3 C 293 [9] the span length of test specimen divided in two portions and the ratio of the straight distance between the point of load
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