Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Citation - WoS: 76Citation - Scopus: 81Influence of NaNo SiO2 and NaNo CaCo3 Particles on Strength, Workability, and Microstructural Properties of Fly Ash-Based Geopolymer(Ernst & Sohn, 2020-05-06) Durak, Ugur; Karahan, Okan; Uzal, Burak; Ilkentapar, Serhan; Atis, Cengiz DuranThe influence of nano SiO2(NS) and CaCO3(NC) particles on the properties of class F fly ash based geopolymer mortar activated with different sodium ion concentrations have been investigated. Mortar mixture proportions were 1:3:0.3 for binder, sand, and water, respectively. Nano SiO2 and CaCO3 particles were replaced with a binder by weight basis at the ratios of 1, 2, and 3% in the mixtures. Sodium concentrations amount used were 8, 10, and 12% Na+ of binder content. Geopolymer mortar samples were cured at 60, 75, and 90 degrees C in a furnace for 24, 48, and 72 hr. After the heat curing process, flexural, and compressive strength tests were performed. The changes in the microstructure of geopolymer due to influence of nanoparticles were examined by utilizing isothermal calorimetric studies on geopolymer paste, and field-emission scanning electron microscopy (FESEM). Based on laboratory work results, it was concluded that for all sodium ion concentrations, the addition of nano SiO2 and CaCO3 particles improved the flexural and compressive strengths after 24 hr heat curing. However, the favorable effects of nanoparticles on strength properties tend to disappear after 48 and 72 hr heat curing. The results of isothermal calorimetric studies showed that nano SiO2 and CaCO3 particles accelerated the geopolymeric reactions at an early age. FESEM results showed that additions of nanoparticles made the microstructure of geopolymer products more intense and compact.Article Citation - WoS: 7Citation - Scopus: 7Effect of Nano-SiO2 on Strength and Hydration Characteristics of Ternary Cementitious Systems(Springer Heidelberg, 2023-05-31) Yorulmaz, Hediye; Uzal, Burak; Karahan, Okan; Durak, Ugur; Ilkentapar, Serhan; Atis, Cengiz DuranThis paper shows results of laboratory study on the effects of nano-SiO2 on Portland cement-fly ash systems. It is aimed to improve performance of fly ash-cement systems, particularly at early age, with the inclusion of nano-SiO2. In order to observe the effects of nano-SiO2 particles on the strength and hydration kinetics of fly ash blended cementitious systems, binary and ternary systems were prepared by adding 0.25-1.5% nano-SiO2 by weight of blended cements. Workability, setting time, water absorption capacity, fire resistance, compressive strength and isothermal calorimeter tests were conducted on the cementitious systems. The results indicate that increasing quantity of fly ash increased workability, setting time, water absorption capacity of cementitious systems, whereas the increasing quantity of nano-SiO2 reduced these values. Significant increment in compressive strength were observed, especially at early ages of fly ash-cement systems with nano-SiO2 addition, compared to fly ash added systems, which may compensate for the decrease in compressive strength caused by fly ash. Nano-SiO2 addition accelerated hydration reactions at early age. By partially eliminating the negative effects of fly ash with nano-SiO2, high rates of fly ash can be used in cementitious systems, thus forming more sustainable systems.Article Citation - WoS: 32Citation - Scopus: 35A 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 DuranIn 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.