Yazar "Gulsan, Mehmet Eren" seçeneğine göre listele

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    Effect of nano-silica on the chemical durability and mechanical performance of fly ash based geopolymer concrete (vol 44, pg 12253, 2018)
    (Elsevier Sci Ltd, 2019) Cevik, Abdulkadir; Alzeebaree, Radhwan; Humur, Ghassan; Nis, Anil; Gulsan, Mehmet Eren
    [Abstract Not Available]
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    Fresh and hardened state performance of self-compacting slag based alkali activated concrete using nanosilica and steel fiber
    (Sage Publications Ltd, 2021) Eren, Necip Altay; Alzeebaree, Radhwan; Cevik, Abdulkadir; Nis, Anil; Mohammedameen, Alaa; Gulsan, Mehmet Eren
    This study investigates the fresh and hardened state performance of slag-based self-compacting alkali-activated concretes (SCAAC) reinforced with steel fibers (SF) and nano-silica (NS), cured at an ambient temperature. Two different hooked-end SF with two fiber volumes and NS were used to examine the combined effect of the SF volume ratio, SF aspect ratio, and NS on the fresh and hardened state performance of SCAAC. In extension, the influence of specimen thickness to steel fiber length (d/F-L) ratio on the failure modes of the bending specimens was evaluated. The fresh state properties were evaluated via T-50 value, slump flow, V-funnel, and L-Box tests, while the hardened state properties were studied through compressive strength, splitting tensile strength, modulus of elasticity, and flexural tensile strength tests. The relationship analyses were carried out among fresh and hardened state properties, and scanning electron microscopy (SEM) was also conducted to examine the microstructure. The results indicated that fresh state performance was favorably affected by NS inclusion but adversely influenced by SF content and aspect ratio. The hardened state performances enhanced with a higher amount of SF volume and an aspect ratio. Also, the NS improved the splitting tensile and flexural strength but decreased the compressive strength and elasticity modulus of the specimens. The d/F-L ratio was found a significant parameter on failure modes, and the specimens having a d/F-L ratio of 3.33 showed flexural cracks. In contrast, the specimens having a d/F-L ratio of 1.25 exhibited inclined flexural-shear cracks, especially for 1% SF.
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    Mechanical and durability properties of fly ash and slag based geopolymer concrete
    (Techno-Press, 2018) Kurtoglu, Ahmet Emin; Alzeebaree, Radhwan; Aljumaili, Omar; Nis, Anil; Gulsan, Mehmet Eren; Humur, Ghassan; Cevik, Abdulkadir
    In this paper, mechanical and short-term durability properties of fly ash and slag based geopolymer concretes (FAGPC-SGPC) were investigated. The alkaline solution was prepared with a mixture of sodium silicate solution (Na2SiO3) and sodium hydroxide solution (NaOH) for geopolymer concretes. Ordinary Portland Cement (OPC) concrete was also produced for comparison. Main objective of the study was to examine the usability of geopolymer concretes instead of the ordinary Portland cement concrete for structural use. In addition to this, this study was aimed to make a contribution to standardization process of the geopolymer concretes in the construction industry. For this purpose; SGPC, FAGPC and OPC specimens were exposed to sulfuric acid (H2SO4), magnesium sulfate (MgSO4) and sea water (NaCl) solutions with concentrations of 5%, 5% and 3.5%, respectively. Visual inspection and weight change of the specimens were evaluated in terms of durability aspects. For the mechanical aspects; compression, splitting tensile and flexural strength tests were conducted before and after the chemical attacks to investigate the residual mechanical strengths of geopolymer concretes under chemical attacks. Results indicated that SGPC (100% slag) is stronger and durable than the FAGPC due to more stable and strong cross-linked alumina-silicate polymer structure. In addition, FAGPC specimens (100% fly ash) showed better durability resistance than the OPC specimens. However, FAGPC specimens (100% fly ash) demonstrated lower mechanical performance as compared to OPC specimens due to low reactivity of fly ash particles, low amount of calcium and more porous structure. Among the chemical environments, sulfuric acid (H2SO4) was most dangerous environment for all concrete types.
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    Mechanical Investigation and Durability of HDPE-confined SCC Columns Exposed to Severe Environment
    (Korean Society Of Civil Engineers-Ksce, 2018) Kurtoglu, Ahmet Emin; Hussein, Ali Khalid; Gulsan, Mehmet Eren; Altan, Mehmet Fatih; Cevik, Abdulkadir
    This paper aims at investigating the mechanical properties and short term durability performance of Self-Compacting Concrete (SCC) - filled High Density Polyethylene (HDPE) tubes with and without steel fibers. A total of 45 cylinder specimens were prepared and subjected to aggressive substances such as sulfate or acid contents. At the end of each exposure, the specimens were instrumented and tested under axial compression. Test variables included the environmental exposure conditions, tube thickness, inside diameter, tube height and steel fiber presence. The load-strain behavior was inspected to evaluate the effect of each exposure. The results indicated that peak load reduction in HDPE-confined specimens is only about 0.3-1% whereas this reduction is around 45-50% for unconfined specimens. In addition, increasing tube thickness by 30% results in up to 50% higher fracture energy. Results also indicate that steel fiber addition has little contribution (0.3-1%) in load capacity whereas the energy absorption capacity is increased up to 20%.
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    Mechanical performance of FRP-confined geopolymer concrete under seawater attack
    (Sage Publications Inc, 2020) Alzeebaree, Radhwan; Cevik, Abdulkadir; Mohammedameen, Alaa; Nis, Anil; Gulsan, Mehmet Eren
    In the study, mechanical properties and durability performance of confined/unconfined geopolymer concrete and ordinary concrete specimens were investigated under ambient and seawater environments. Some of the specimens were confined by carbon fiber and basalt fiber-reinforced polymer fabric materials with one layer and three layers under chloride and ambient environments to observe mechanical strength contribution and durability performances of these hybrid types of materials. These fiber-reinforced polymer fabric materials were also evaluated in terms of retrofit purposes especially in the marine structures. In addition, microstructural evaluation is also conducted using scanning electron microscope on geopolymer concrete and ordinary concrete specimens to observe the amount of deterioration in microscale due to the chloride attacks. Results indicated that confined specimens exhibited enhanced strength, ductility, and durability properties than unconfined specimens, and the degree of the enhancement depended on the fiber-reinforced polymer confinement type and the number of fiber-reinforced polymer layer. Specimens confined by carbon fabrics with three layers showed superior mechanical properties and durability performance against chloride attack, while specimens confined by basalt fabrics with one layer exhibited low performance, and unconfined specimens showed the worst performance. Both fiber-reinforced polymer fabric materials can be utilized as retrofit materials in structural elements against chloride attacks. The results also pointed out that seawater attack reduced the ductility performance of the geopolymer concrete and ordinary concrete specimens. Furthermore, geopolymer concrete specimens were found more durable than the ordinary concrete specimens, and both types of concretes exhibited similar fracture properties, indicating that geopolymer concrete can be utilized for structural elements instead of ordinary concretes.
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    Performance of FRP confined and unconfined engineered cementitious composite exposed to seawater
    (Sage Publications Ltd, 2019) Mohammedameen, Alaa; Cevik, Abdulkadir; Alzeebaree, Radhwan; Nis, Anil; Gulsan, Mehmet Eren
    Conventional concrete suffers from brittle failures under mechanical behaviour, and lack of ductility results in the loss of human life and property in earthquake zones. Therefore, the degree of ductility becomes significant in seismic regions. This paper investigates the influence of poly-vinyl alcohol fibers, basalt fiber-reinforced polymer (BFRP) and carbon fiber-reinforced polymer (CFRP) fabrics on the ductility and mechanical performance of low (LCFA) and high (HCFA) calcium fly ash-based engineered cementitious composite concrete. The study also focuses on the mechanical behaviour of the CFRP and BFRP materials using different matrix types exposed to 3.5% seawater environment. Cyclic loading and scanning electron microscopy observations were also performed to see the effect of chloride attack on mechanical performance and ductility of the specimens. In addition, utilization of CFRP and BFRP fabrics as a retrofit material is also evaluated. Results indicated that the degree of ductility and mechanical performance were found to be superior for the CFRP-engineered cementitious composite hybrid specimens under ambient environment, while LCFA-CFRP hybrid specimens showed better performance under seawater environment. The effect of matrix type was also found significant when engineered cementitious composite is used together with fiber-reinforced polymer materials. In addition, both fiber-reinforced polymer materials can be used as a retrofit material under seawater environment.