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    Bond Performance of GFRP Bars in Glass and Basalt Fiber-Reinforced Geopolymer Concrete Under Hinged Beam Tests
    (MDPI, 2025) Erturkmen, Duygu; Urunveren, Husamettin; Beycioglu, Ahmet; Ibadov, Nabi; Aruntas, Hueseyin Yilmaz; Garbacz, Andrzej
    In recent years, researchers have focused on the usability of fiber-reinforced polymer (FRP) bars due to their lightweight, corrosion-resistant, and eco-friendly characteristics. Geopolymers, as low-carbon alternatives to traditional binders, aim to reduce CO2 emissions in concrete production. The bond strength between FRP bars and concrete is critical for the load-bearing capacity and deformation characteristics of reinforced elements. The objectives of this work are to investigate the bond performance of GFRP bars in chopped glass and basalt fiber-added geopolymer concrete using hinged beam tests. Since the hinged beam test accurately represents the behavior of real bending elements, this test method was selected as a main bonding test. Initially, three geopolymer mixtures with Ms modulus values of 1.2, 1.3, and 1.4 were prepared and tested. The mixture with a modulus of 1.2 Ms, achieving a compressive strength of 56.53 MPa, a flexural strength of 3.54 MPa, and a flow diameter of 57 cm, was chosen for beam production due to its optimal workability and strength. After mechanical and workability tests, SEM analysis was performed to evaluate its internal structure. For evaluating the bond performance of GFRP bars, 12 geopolymer beam specimens were prepared, incorporating varying fiber types (chopped glass fiber or basalt fiber) and embedment lengths (5 & Oslash; or 20 & Oslash;). Hinged beam tests revealed that the bond strengths of glass and basalt fiber-added mixtures were up to 49% and 37% higher than that of the control geopolymer concrete, respectively. It was concluded that incorporating fibers positively influenced the bond between geopolymer concrete and GFRP bars, with glass fibers proving more effective than basalt fibers. These findings enhance the understanding of bond mechanisms between GFRP bars and geopolymer concrete, emphasizing their potential for sustainable and durable construction in both industrial and scientific applications.
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    Effect of Glass and Basalt Fibers on the Bond-Slip Behavior of Steel Rebar in Eco-Friendly Fly Ash-Based Geopolymer Concrete: A Relative Comparison Using the Hinged Beam Approach
    (ASCE-AMER Society of Civil Engineers, 2025) Erturkmen, Duygu; Urunveren, Husamettin; Beycioglu, Ahmet
    Geopolymers, a type of concrete extensively researched in recent years, demonstrate mechanical properties comparable to conventional concrete. It is widely acknowledged that the main aim of adding fibers to conventional or geopolymer concrete is to improve its flexural and tensile strength. However, there remains a notable gap in the literature regarding the impact of fibers on the bond between reinforcement bars and geopolymer concrete. This paper presents the findings of an experimental investigation of the effect of glass and basalt fibers on the bond stress behavior of eco-friendly fly ash-based geopolymer concrete. The study explores the bond performance of fiber-reinforced geopolymer concrete specimens, considering fiber type and amount as experimental variables. To this end, beam samples with different fiber types (basalt or glass), fiber amounts (2 kg/m3 or 4 kg/m3), and embedment lengths (5 & Oslash; or 20 & Oslash;) were produced. Hinged beam bending tests were conducted on the prepared specimens after heat curing at 100 degrees C for 24 h. The experimental results reveal that both types of fibers positively influence the bond behavior of the geopolymer concrete. Additionally, the bond stress values of glass fiber-reinforced geopolymer concrete specimens were found to be slightly higher than those of basalt fiber-reinforced counterparts. Furthermore, it was observed that maximum bond stress values decrease with increasing fiber content and embedment length for both glass and basalt fiber specimens.
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    Öğe
    Investigation of the behavior of carbon fiber reinforced polymer confined standard cylinder concrete specimens under axial load
    (Pamukkale Univ, 2017) Erturkmen, Duygu; Dundar, Cengiz; Tokgoz, Serkan
    The use of fiber reinforced polymer composites for strengthening in concrete structures has become quite prevalent in recent years. Especially, to provide ductile behavior from the structural elements that produced by using the high strength concrete under the load effects, the externally wrapping of these elements with using the fiber reinforced polymer materials comes into prominence as an alternative method for strengthening. These materials with high tensile strength can often be preferred due to their lightweight and easy to apply. In this study, cylinder-shaped concrete specimens with compressive strengths range between 53.13 similar to 74.87 MPa, are wrapped one or two layer with using bi-directional carbon fiber reinforced fabric (CFRP). These wrapped specimens were tested under the axial comprehensive loads and the effects of the CFRP wrapping on concrete strength and ductility was investigated. In addition, stress-strain relations obtained from the tested specimens were compared with the results of existing models for strengthened cylindrical specimen with CFRP in literature. As a result a significant increase was obtained in the compressive strength and deformation capacity of CFRP wrapped specimens. Especially, it was observed that the stress-strain values obtained from the two layers CFRP wrapped specimens show good agreement with the values obtained from the models.