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    The use of high-volume hybrid steel fiber instead of compression rebar to improve the structural performance of high-strength SCC beams under bending
    (Elsevier Sci Ltd, 2025) Turk, Kazim; Katlav, Metin; Bitkin, Rifat Enes
    This article offers exhaustive experimental research on the effect of different fiber volumes (1.00 % and 1.50 %) and combinations (single and hybrid) instead of compression reinforcing bars on the structural performance of reinforced concrete (RC) beams fabricated from high-strength self-compacting concrete (SCC). Within the scope of the research, the fresh concrete properties of five different designed SCC mixes were determined in accordance with EFNARC guidelines. A total of ten full-scale SCC beams with the sizes of 200 x 300 x 2000 mm, two from each mix, were manufactured and tested under bending load after a curing period of 90 days. The test outcomes were compared and analyzed in detail with respect to key structural behavior parameters, such as the loadmidspan deflection relationship, toughness, ductility, crack patterns, and failure modes. Additionally, a design approach for predicting the nominal flexural capacity of high-strength SCC beams containing high-volume steel fibers is proposed with some assumptions as per the ACI 544. The experimental results indicate that the inclusion of steel fibers instead of compression reinforcing bars in high-strength SCC beams markedly improved the structural performance; specifically, the high-volume hybrid steel fiber reinforcement (1.20 % macro steel and 0.30 % micro steel by volume) resulted in outstanding structural performance compared to other fiber volumes and combinations reinforcement. That is to say, the peak load, toughness, and deflection ductility index values of the SCC beams incorporating this high-volume hybrid steel fiber were obtained at 1.36, 2.01, and 1.39 times higher, respectively, in comparison to the non-fiber Control SCC beams with compression reinforcing bars. All in all, the use of high-volume hybrid steel fiber in place of intensive compression reinforcing bars to cover long spans in RC beams can significantly cut time in the construction process, as well as reduce labor and material costs, allowing for a more eco-friendly and cost-effective design process.
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    Workability, strength and flexural toughness properties of hybrid steel fiber reinforced SCC with high-volume fiber
    (Elsevier Sci Ltd, 2021) Turk, Kazim; Bassurucu, Mahmut; Bitkin, Rifat Enes
    The purpose of this study was to investigate the effect of total volume fraction and combinations of macro and micro steel fiber on the workability and mechanical as well as flexural performance of hybrid reinforced self-compacting concretes (HFR-SCC). A sum of five fiber reinforced SCC mixtures containing a total volume fraction fiber of 1.00% and 1.50% were designed as two single fiber reinforced mixtures with only macro steel fiber and two hybrid fiber reinforced as well as the control mixture without fiber. To interpret the fresh properties of HFR-SCC, slump flow diameter, T-500 and J-ring test were performed. The compressive strength, splitting tensile strength, flexural strength, load-carrying capacity, flexural toughness and ductility were measured to evaluate the mechanical and flexural performance of HFRSCC. The attained test results for fresh properties revealed that although decrease in the workability of FR-SCC mixtures happened with the increase in total volume fractions of fibers, all steel fiber reinforced SCC mixtures provided the workability limits of EFNARC. The flexural toughness values increased with the total volume fraction of fibers from 1.00% to 1.50%. The hybrid reinforced SCC specimens were exhibited superior the compressive strength, flexural toughness and ductility compared to single fiber reinforced SCC specimens. Also, HFR-SCC mixture with 1.20% macro and 0.30% micro steel fibers gave the best results in terms of mechanical and flexural performance due to increase in macro steel fiber volume fraction and higher fiber reinforced index with 1.04 as well as synergistic blends of macro and micro steel fibers. (C) 2020 Elsevier Ltd. All rights reserved.