Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Citation - WoS: 130Citation - Scopus: 157Thermal Conductivity, Compressive Strength and Ultrasonic Wave Velocity of Cementitious Composite Containing Waste PET Lightweight Aggregate (WPLA)(Elsevier Sci Ltd, 2013-02) Akcaozoglu, Semiha; Akcaozoglu, Kubilay; Atis, Cengiz DuranIn this study, the influence of waste PET as lightweight aggregate (WPLA) replacement with conventional aggregate, on thermal conductivity, unit weight and compressive strength properties of concrete composite was investigated. For this purpose, five different mixtures were prepared (the control mixtures and four WPLA mixtures including 30%, 40%, 50%, and 60% waste PET aggregate by volume). Thermal conductivity (TC) coefficients of the specimens were measured with guarded hot plate apparatus according to TS ISO 8302 [1]. The thermal conductivity coefficient, unit weight and compressive strength of specimens decreased as the amount of WPLA increased in concrete. The minimum thermal conductivity value was 0.3924 W/m K, observed at 60% WPLA replacement. From this result, it was concluded that waste PET aggregates replacement with conventional aggregate in the mixture showed better insulation properties (i.e. lower thermal coefficient). Due to the low unit weight and thermal conductivity values of WPLA composites, there is a potential of using WPLA composites in construction applications. (c) 2012 Elsevier Ltd. All rights reserved.Article Citation - WoS: 9Citation - Scopus: 9Reaction 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 DuranThis 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: 127Citation - Scopus: 138Influence of Admixtures on the Properties of Alkali-Activated Slag Mortars Subjected to Different Curing Conditions(Elsevier Sci Ltd, 2013-02) Bilim, Cahit; Karahan, Okan; Atis, Cengiz Duran; Ilkentapar, SerhanThis paper presents the influence of shrinkage-reducing (SHR) and superplasticizing and set-retarding admixtures (SSRe) on the properties of slag pastes and mortars activated by liquid sodium silicate with different dosage and modulus ratio. Properties in the fresh and hardened state for these binders were investigated by means of measuring some properties including setting time, flowability, flexural strength, compressive strength, carbonation and shrinkage. In this study, fifteen pastes and mortars were prepared. Liquid sodium silicate was used to activate the slag at two sodium concentrations, 4% and 6% by mass of slag. Liquid sodium silicate and sodium hydroxide were blended to obtain 0.75 and 1 modulus ratio of SiO2/Na2O. Results showed that although the higher percentage of sodium in the activator produced a higher strength, workability and setting times rapidly decreased with the higher sodium concentration due to instantaneous reaction and quick hardening of slag activated by liquid sodium silicate. None of the admixtures generally had an impact on the setting times of alkali-activated slag (AAS) pastes. SSRe admixture increased the flow rate of AAS mortars while SHR admixture partially affected the flow values of AAS mortars. SHR admixture exhibited a slight decrease in the carbonation depths of AAS mortars. SSRe and particularly SHR chemical admixtures reduced the shrinkage of AAS mortars. However, the shrinkage values of AAS mortars still were higher than those of ordinary Portland cement (NPC) mortars. Curing conditions had a significant effect on the mechanical behavior in the hardened state of AAS mortars compared to NPC mortars. (C) 2012 Elsevier Ltd. All rights reserved.Article Citation - WoS: 77Citation - Scopus: 92Effect of Granulated Blast Furnace Slag and Fly Ash Addition on the Strength Properties of Lightweight Mortars Containing Waste PET Aggregates(Elsevier Sci Ltd, 2011-10) Akcaozoglu, Semiha; Atis, Cengiz Duran; Akaözolu, Semiha; Ati, Cengiz DuranIn this work, the effect of Granulated Blast Furnace Slag (GBFS) and fly ash (FA) addition on the strength properties of lightweight mortars containing waste Poly-ethylene Terephthalate (PET) bottle aggregates was investigated. Investigation was carried out on three groups of mortar specimens. One made with only Normal Portland cement (NPC) as binder, second made with NPC and GBFS together and, third made with NPC and FA together. The industrial wastes mentioned above were used as the replacement of cement on mass basis at the replacement ratio of 50%. The size of shredded PET granules used as aggregate for the preparation of mortar mixtures were between 0 and 4 mm. The waste lightweight PET aggregate (WPLA)-binder ratio (WPLA/b) was 0.60; the water-binder (w/b) ratios were determined as 0.45 and 0.50. The dry unit weight, compressive and flexural-tensile strengths, carbonation depths and drying shrinkage values were measured and presented. The results have shown that modifying GBFS had positive effects on the compressive strength and drying shrinkage values (after 90 days) of the WPLA mortars. However, FA substitution decreased compressive and flexural-tensile strengths and increased carbonation depths. Nevertheless a visible reduction occurred on the drying shrinkage values of FA modifying specimens more than cement specimens and GBFS modified specimens. The test results indicated that, GBFS has a potential of using as the replacement of cement on the WPLA mortars by taking into consideration the characteristics. But using FA as a binder at the replacement ratio of 50% did not improve the overall strength properties. Although it was thought that, using FA as binder at the replacement ratio of 50% for the aim of production WPLA concrete which has a specific strength, would provide advantages of economical and ecological aspects. (C) 2011 Elsevier Ltd. All rights reserved.Article Citation - WoS: 108Citation - Scopus: 124Dual Effectiveness of Freezing-Thawing and Sulfate Attack on High-Volume Slag-Incorporated ECC(Elsevier Sci Ltd, 2013-02) Ozbay, Erdogan; Karahan, Okan; Lachemi, Mohamed; Hossain, Khandaker M. A.; Atis, Cengiz DuranThis study investigated the dual effect of freeze-thaw cycles with sodium sulfate solution on the performance of non-air-entrained Engineering Cementitious Composites (ECCs) with high volumes of slag. ECC specimens containing three different levels of slag content as a replacement for cement (55%, 69% and 81% by weight of total cementitious material) were exposed to aggressive sodium sulfate solution under freezing-thawing cycles. The load-deflection response associated with ultimate mid-span deflection and flexural strength/stiffness was determined, along with crack development behavior. For comparison purposes, the freezing-thawing resistance (in water) of control ECC specimens was also evaluated. Modified point count method air-void parameters, compressive strength, porosity, water absorption and sorptivity tests were also conducted on the virgin ECC specimens (those not exposed to freezing-thawing cycles in water or aggressive sodium sulfate solution). The test results for the virgin specimens revealed that increased slag content (S/PC) improved the ductility, hardened air content, water absorption, porosity and sorptivity of ECC, while marginally decreasing the compressive and flexural strengths. Freeze-thaw cycles in water or sodium sulfate solution showed that the ductility of ECC specimens decreased remarkably, irrespective of slag content and applied freezing-thawing process. Reduction in mass loss was at minimal levels and no significant behavior change was monitored between the specimens undergoing freeze-thaw cycling in water and the aggressive sodium sulfate solution. Moreover, the decrease in flexural stiffness was more evident than the reduction of the flexural strength for all ECC mixtures. Crown Copyright (c) 2012 Published by Elsevier Ltd. All rights reserved.Article Citation - WoS: 8Citation - Scopus: 8Characterizing 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 DuranSince 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: 81Citation - Scopus: 91Alkali Activation of Mortars Containing Different Replacement Levels of Ground Granulated Blast Furnace Slag(Elsevier Sci Ltd, 2012-03) Bilim, Cahit; Atis, Cengiz Duran; Ati, Cengiz DuranThe aim of the present study is to investigate some properties of alkali-activated mortars containing slag at different replacement levels. Ground granulated blast furnace slag was used at 0%, 20%, 40%, 60%, 80% and 100% replacement by weight of cement, and liquid sodium silicate having three different Na dosages was chosen as the alkaline activator. In this research, carbonation resistance measurements and compressive and flexural strength tests were performed on the mortar specimens with size of 40 x 40 x 160 mm. The findings obtained from the tests showed that carbonation depth values of the mortars decreased with the increase of activator dosage. Additionally, compressive and flexural strength values increased with the increase in activator concentration and slag replacement level. Portland cement/slag mortars activated by liquid sodium silicate exhibited lower strength than the slag alone activated by the same activator. (C) 2011 Elsevier Ltd. All rights reserved.