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Scopus İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395

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Author: search.filters.author.Uzal, BurakWoS Q: search.filters.wosQuartile.Q1

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Now showing 1 - 6 of 6
  • Article
    Citation - WoS: 12
    Citation - Scopus: 14
    Role of Inclusion Size Distribution of Titanium Dioxide on the Nitrogen Oxides Reduction Capability and Microstructural Characteristics of Cementitious Systems
    (Elsevier Sci Ltd, 2022-02) Bahsi, Emrah; Sahin, Oguzhan; Ilcan, Huseyin; Uzal, Burak; Gunal, Muhammed Faruk; Yildirim, Gurkan; Sahmaran, Mustafa
    This paper explores the effect of the inclusion size of titanium dioxide (TiO2) particles on a variety of performance properties of cementitious systems via experimental studies. In addition to comprehensive microstructural analysis including pore size distribution and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) analyses, particular consideration was given to the effect of particle size distribution (PSD) of TiO2 particles on mechanical and photocatalytic properties and hydration kinetics of cementitious systems. Nano-sized, submicron-sized and micron-sized anatase-phase TiO2 powders were utilized as photocatalysts at a dosage of 5% by total weight of powder material. In addition to the single use of TiO2 particles with three different size ranges (nano, submicron and micron), they were also used in combination by adjusting their PSDs with three different PSD moduli (q): 0.1, 0.5, and 0.9. Test results show that techniques for achieving optimal microstructural characteristics of cementitious systems also help design and improve their performance in favor of multifunctionality. As a result of PSD optimization of TiO2 particles with three different size ranges, which was significantly influential on the microstructure of the cementitious systems, superior photocatalytic degradation results were obtained from mixtures containing lower amounts of nano-sized TiO2 particles. Cementitious composites with denser microstructure showed lower performance in terms of being able to maintain photocatalytic degradation capability for a prolonged period, whereas the opposite was the case for compressive strength.
  • Article
    Citation - WoS: 10
    Citation - Scopus: 10
    Reaction Kinetics and Properties of Pumice-Based Geopolymer Systems Cured at Room Temperature
    (Elsevier Sci Ltd, 2023-12) Kucukyildirim, Enver; Yorulmaz, Hediye; Durak, Ugur; Ilkentapar, Serhan; Uzal, Burak; Karahan, Okan; Atis, Cengiz Duran
    This research investigated the kinetics of pumice-based geopolymer systems and their physical and mechanical properties. The effect of the Na2SiO3/NaOH ratio of geopolymer systems on the rate of heat evolution and total heat of reaction were examined via isothermal calorimetry of geopolymer pastes prepared with Na2SiO3/NaOH ratios of 2.5, 3, and 3.5. Hardened pastes were also studied with thermo-gravimetric analysis to determine weight loss. In addition, the unit weights and compressive strengths of the pastes prepared using pumice were measured. Although the hydration process starts the earliest in pumice-based geopolymer pastes with a Na2SiO3/ NaOH ratio of 2, they have the lowest total hydration temperature. Na2SiO3/NaOH ratio of 2.5 by mass, shows higher weight loss obtained from TGA results. The compressive strength of the paste sample, prepared with a Na2SiO3/NaOH ratio of 3.5 by mass, was the highest, with 36.30 MPa at 28d. Depending on the Na2SiO3/NaOH ratio, it is thought that as the amount of Na2SiO3 increases in the samples, silica gel formation increases in later ages.
  • Article
    Citation - WoS: 22
    Citation - Scopus: 23
    Practical Charts to Identify the Predominant Clay Mineral Based on Oxide Composition of Clayey Soils
    (Elsevier, 2017-01) Sivrikaya, Osman; Uzal, Burak; Ozturk, Yunus Emre
    This study proposes some useful practical charts representing the relationships between oxide composition and the type of predominant clay mineral present in clay soils. In order to produce the charts, the data set are collected from published literature. Some useful classification schemes for predominant clay mineral type were obtained by using binary and ternary graphs of oxide composition data. The most successful relations indicating the type of clay mineral have been found on SiO2 versus Al2O3 + Fe2O3 + FeO, SiO2 versus MgO + CaO + Na2O + K2O binary plots, SiO2 Al2O3 Others and SiO2 - Al2O3 - K2O ternary plots. (C) 2016 Elsevier B.V. All rights reserved.
  • Article
    Citation - WoS: 19
    Citation - Scopus: 21
    Effect of Characteristics of Natural Zeolites on Their Geopolymerization
    (Elsevier, 2021-12) Ozen, Sevgi; Uzal, Burak
    The properties of clinoptilolite-based geopolymers are investigated with a focus on the parameters affecting the reactivity of clinoptilolite in a geopolymer binder. A complete characterization of raw materials was carried out as well as a determination of the mineralogical composition, microstructure and mechanical properties of geopolymers. The results of the investigation show that of the investigated materials, geopolymer made with clinoptilolite-bearing tuff from Bayburt has the highest compressive strength. The chemical and mineralogical characteristics of a raw material are important parameters that potentially control the geopolymeric reaction, whereas physical properties (particle size and BET specific surface area) are mainly influential at early stages of geopolymerization. Geopolymeric gel was found to be the main reaction product through characterization by XRD and SEM analysis. The geopolymer produced with the raw material from Bayburt had a narrow range of Si/Al ratios and possessed a geopolymer binder structure with an advanced nature. Lastly, in addition to clinoptilolite, feldspar has an additional effect on the geopolymeric reaction and enhances the process, especially at later ages.
  • Article
    Citation - WoS: 10
    Citation - Scopus: 10
    Characterizing Boron-Enhanced One-Part Alkaline-Activated Mortars: Mechanical Properties, Microstructure and Environmental Impacts
    (Elsevier Sci Ltd, 2024-05) Orklemez, Ezgi; Ilkentapar, Serhan; Durak, Ugur; Gulcimen, Sedat; Uzal, Nigmet; Uzal, Burak; Atis, Cengiz Duran
    Since alkali activators negatively effect the environmental impact assessment, it is necessary to develop the alternative activators from natural sources with low environmental impact. Therefore, in this study, the usage of boron refined products colemanite, ulexite and boron pentahydrate as activators in slag-based alkali-activated mortar systems was investigated in detail. Flexural and compressive strength tests, isothermal calorimetry measurement, thermogravimetric and differential thermal analysis, inductively coupled plasma mass spectrometry analysis, field emission scanning electron microscopy, and energy dispersive analysis and elemental mapping and X-ray diffraction analysis were carried out on the samples. In addition, sample production was subjected to life cycle analysis (LCA) with a cradle-to-gate approach using two different transportation scenarios. According to the results obtained, it was determined that colemanite, ulexite and boron penta hydrate, when used in optimum proportions, had a positive effect on strength (up to increase 40% compressive strength by 20% ulexite replacement) and could be used as an activator in slag-based alkali-activated systems. The positive results obtained in strength as a result of using boron-refined products are also supported by other test results conducted within the scope of the study. Furthermore, according to the LCA results, it was observed that there was a significant decrease in global warming potential with the substitution of 20% colemanite, ulexite or boron pentahydrate as activators, not only compared to the reference sample but also traditional cementitious systems.
  • Article
    Citation - WoS: 36
    Citation - Scopus: 40
    A New Parameter Influencing the Reaction Kinetics and Properties of Fly Ash Based Geopolymers: A Pre-Rest Period Before Heat Curing
    (Elsevier, 2021-03) Durak, Ugur; Ilkentapar, Serhan; Karahan, Okan; Uzal, Burak; Atis, Cengiz Duran
    In this study, the influence of a pre-rest period before heat curing (as a new parameter), on the physical properties, flexural and compressive strength, and microstructure of geopolymer mortars and pastes produced with alkali activation of fly ash were investigated. In this context, geopolymer mortar and paste samples were prepared and pre-rested under laboratory conditions for 0, 1, 2, 3, 7, 14, and 28 days before heat curing. After the pre-rest period, the samples were subjected to heat curing at 75 degrees C in an oven, for 2 days. Mortar and paste samples exposed to a pre-rest period while in the fresh state before heat curing were compared with control samples without pre-resting. Water absorption, porosity, specific gravity, capillarity, flexural strength, compressive strength, and abrasion resistance tests were conducted on the geopolymer mortar samples. A reaction kinetics study using an isothermal calorimeter, XRD, and SEM analyses were performed on the geopolymer paste samples for microstructural investigations. Based on the results obtained, it was observed that the mechanical strength of the samples subjected to the pre-rest period before heat curing increased considerably compared to the reference (without pre-resting) samples. In addition, because of pre-resting, the capillarity coefficient, water permeability, and porosity of the samples decreased compared to the reference samples, and it was concluded that pre-resting improves durability-related properties. Moreover, the reaction kinetics and SEM analysis results, supporting the above findings, showed that a pre-resting period increases the geopolymeric reaction products and causes a denser microstructure.