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    Effect of macro and micro fiber volume on the flexural performance of hybrid fiber reinforced SCC
    (Techno-Press, 2020) Turk, Kazim; Kina, Ceren; Oztekin, Erol
    The aim of this study is to investigate the flexural performance of hybrid fiber reinforced self-compacting concrete (HFRSCC) having different ratio of micro and macro steel fiber. A total of five mixtures are prepared. In all mixtures, the sum of the steel fiber content is 1% and also water/binder ratio is kept constant. The amount of high range water reducer admixture (HRWRA) is arranged to satisfy the workability criteria of self-compacting concrete. Four-point bending test is carried out to analyze the flexural performance of the mixtures at 28 and 56 curing days. From the obtained load-deflection curves, the load carrying capacity, deflection and toughness values are investigated according to ASTM C1609, ASTM C1018 and JSCE standards. The mixtures containing higher ratio of macro steel fiber exhibit numerous micro-cracks and, thus, deflection-hardening response is observed. The mixture containing 1% micro steel fiber shows worst performance in the view of all flexural parameters. An improvement is observed in the aspect of toughness and load carrying capacity as the macro steel fiber content increases. The test results based on the standards are also compared taking account of abovementioned standards.
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    Investigation of shear strength of SCC beams with hybrid fiber as experimental and statistical
    (Yildiz Technical Univ, 2023) Turk, Kazim; Bassurucu, Mahmut; Oztekin, Erol
    In this study, the effects of different blending and combination of macro and micro steel fibers on the shear strength, ductility, failure mode and crack propagation of hybrid fiber reinforced self-compacting concrete beams were investigated experimentally and statistically. In the design of concrete, straight steel micro and hooked steel macro fibers were used. For this purpose, twelve 200x200x1000 mm reinforced concrete beam specimens, which had same reinforcing bar details, were produced and tested under four-point bending to investigate ultimate shear strength, displacement ductility, crack patterns, mode of failure, energy absorption capacity and yield stiffness properties. In conclusion, the beam specimens produced from self-compacting concrete (SCC) with hybrid steel fiber prevented the shear failure while all SCC beam specimens containing hybrid steel fiber reached the ultimate bearing capacity with the mode of flexural failure. Also, it can be clearly emphasized that the SCC beam specimens with hybrid steel fiber had higher shear strength, energy absorption capacity and yield stiffness than those of beam specimens containing only macro or micro steel fiber.
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    Self-compacting concrete with blended short and long fibres: experimental investigation on the role of fibre blend proportion
    (Taylor & Francis Ltd, 2022) Turk, Kazim; Oztekin, Erol; Kina, Ceren
    In this paper, micro and macro steel fibres were used to understand the influences of blended fibre addition on the fresh and hardened properties of self-compacting concrete (SCC). Five mixtures containing micro and macro steel fibres were prepared in different combinations and in each mixture, the sum of the steel fibre content was kept constant as 1%. To measure the workability of fibre-reinforced self-compacting concrete (FR-SCC), slump-flow diameter, t(500) and J-ring tests were conducted. The results indicated that when the micro steel fibre ratio became more than 0.25%, the fresh properties of SCC were affected negatively. To determine the hardened properties of FR-SCC mixtures, compressive, splitting tensile and flexural tensile strength tests were performed and also ultrasonic pulse velocity (UPV) of the specimens was measured. The micro steel fibre inclusion had positive effect on compressive strength while it caused a reduction in splitting tensile and flexural tensile strength. With regard to the crack formation, in the mixtures having higher content of macro steel fibre, multiple crack behaviour was observed. Moreover, it was revealed from the results that the mixtures exhibited deflection-hardening response in the case of inclusion higher amount of macro steel fibre.