ORAL REFERENCE: ICF100692OR EFFECT OF CRACKING ON SERVICEABILITY OF FIBROUS CONCRETE T. Ayano1, M. A. Wafa1 and K. Sakata2 1The Graduate School of Natural Science and Technology, Okayama University, 3-1-1, Tsushima-naka, Okayama 700-8530, JAPAN 2Department of Environmental and Civil Engineering, Faculty of Environmental Science and Technology, Okayama University, 3-1-1, Tsushima-naka, Okayama 700-8530, JAPAN ABSTRACT In many types of concrete structure loss the serviceability due to wide cracking or large deflection, and it should be repair it as early as possible. As very important structures, such as the tunnel of super express railway, which has a drop of concrete fragment, was a lead to severe social accident. The fiber is expected to be useful in order to improve the serviceability and to prevent a drop of concrete fragment. The performance of concrete with fibers is judged by the flexural toughness obtained by load-deflection curves. The flexural toughness of concrete is different by the different types of fiber and it can express well the toughness of RC members at failure. Sometimes, it is difficult to use the flexural toughness in order to judge the behavior of concrete structures under service load. From the result of cracking on concrete beam cyclic applied load, the necessity of adequate method to judge the performance of concrete with different types of fiber is discussed. KEYWORDS Cracking, serviceability, flexural toughness, polypropylene fibers, steel fibers INTRODUCTION There are several types of fiber for concrete. They have their own characteristic, such as, steel fibers has high dynamical performance, but it is rust [1, 2]. On the other hand, polypropylene fibers is elastic and flexible, it does not pierce the hands or the feet of the workers under construction. But concrete with polypropylene fibers can not be expected as high toughness at failure as concrete with steel fibers [3]. Because the Young’s modulus of polypropylene fibers is about one tenth that of steel fibers, almost it is the same as that of concrete. If the fibers is used in order to improve the toughness of concrete structures at failure, steel fibers may be the best and the flexural toughness obtained by load-deflection curves is good remarks to express the performance of concrete with fibers. The purpose of the usage of fibers is diversified. Sometimes, it is used to restrict the cracking due to drying, or it is used to prevent the spalling of concrete fragment [4, 5]. Recently, the fibers are also used in order to improve the serviceability of concrete structures. In these cases, it may be inadequate to use the flexural toughness to decide the type of fiber to be used.
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