Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Failure Mechanisms and Damage Evolution of Geopolymer Concrete Beams under Flexural Loading: Experimental Investigation and Finite Element Analysis(SAGE Publications Inc, 2026) Ozbayrak, Ahmet; Aslanbay, Yuksel Gul; Aslanbay, Huseyin Hilmi; Altun, Fatih; Kucukgoncu, HurmetThis study investigates the failure behavior and damage mechanisms of geopolymer concrete (GPC) and ordinary Portland cement (OPC) reinforced concrete beams through a combined experimental and numerical approach. Flexural tests were conducted, and then displacement and crack development were monitored using high-precision total station measurements. Numerical analyses were performed using ABAQUS, and the consistency between experimental observations and numerical predictions was evaluated at yield and failure stages to characterize inelastic behavior and damage progression. The effects of key parameters, including tensile reinforcement ratio, geopolymer concrete formulations, and curing methods, on cracking behavior, stiffness degradation, and failure modes were investigated in detail. The results indicate that increasing the tensile reinforcement ratio enhances flexural stiffness and load-bearing capacity while reducing ductility at advanced damage stages. Compared to OPC beams, GPC beams exhibited narrower and more distributed crack patterns due to their distinct microstructural characteristics. Quantitatively, GPC beams exhibited approximately 15% greater deformation in the compression zone at failure, while tensile reinforcement strains were up to 23% higher at yield compared to OPC beams. In addition, the maximum crack width at failure in GPC beams was approximately 50% lower than that of OPC beams. These results indicate that, despite similar strength levels, GPC beams exhibit higher deformation capacity and more distributed damage behavior. The findings demonstrate that geopolymer concrete exhibits distinct failure characteristics compared to OPC and should be explicitly considered in structural design to improve damage control and failure prediction. Overall, the study highlights the potential of geopolymer concrete as a reliable and sustainable structural material.Article Citation - WoS: 3Citation - Scopus: 3Equivalent Stress Block Parameters for Fly Ash-Based Geopolymer Concrete Structural Elements(Ernst & Sohn, 2025-03-06) Ozbayrak, Ahmet; Kucukgoncu, HurmetResearch on the design of structural members made from geopolymer concrete (GPC) remains limited. This study investigates the applicability of equivalent rectangular stress block parameters, traditionally used for reinforced concrete design, in GPC structural elements. We conducted experimental tests on 20 columns (16 GPC, 4 Ordinary Portland Cement [OPC]) and 15 beams (12 GPC, 3 OPC) produced using fly ash-based GPC and standard OPC. These tests involved subjecting the specimens to various loading conditions to measure their ultimate compressive strength and strain. The findings demonstrate that these factors significantly influence the stress block parameters in GPC samples. Notably, parameters k(1) and k(3) were compatible with ACI 318 and Eurocode 2 standards, with deviations within acceptable limits, supporting GPC's potential for use in conventional reinforced concrete frameworks. The study also reveals that GPC columns and beams have higher balanced reinforcement ratios than OPC, due to GPC's increased deformation capacity and strain values. According to the results, the average balanced reinforcement ratio of GPC column specimens is 30% higher than that of OPC, while that of GPC beam specimens is 6% higher. Variations in alkaline activation and curing methods did not significantly impact the equivalent stress block parameters. The change between the average equivalent stress block parameters obtained from GPC and OPC beam samples varies between 1% and 5%, while the change in column samples is around 1%. Although the longitudinal reinforcement ratios in the tests are variable, the averages of the calculated equivalent stress block parameters are close. The experimental results align with numerical analysis, emphasizing GPC's suitability as an alternative material in structural applications. These findings provide a basis for incorporating GPC into existing design standards, with adjustments for its distinct mechanical behavior.