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: 6Citation - Scopus: 6The Influence of Cement Kiln Dust on Strength and Durability Properties of Cement-Based Systems(Springer Heidelberg, 2022-06-06) Hakkomaz, Hadiye; Yorulmaz, Hediye; Durak, Ugur; Ilkentapar, Serhan; Karahan, Okan; Atis, Cengiz DuranThere are very few studies in the literature on the usage of CKD in cementitious systems. This article presents the laboratory study results on the influence of cement kiln dust (CKD) on the properties of mortar made with cement kiln dust and Portland cement. The article aims to prevent CKD's (known as a hazardous waste product) damage to nature by utilizing CKD in cementitious systems and contributing to sustainability by reducing cement amount in the cementitious system. For this purpose, 5%, 10%, 15%, and 20% of CKD were replaced with cement and binary cementitious systems were formed. For all mortar mixes, the water/binder ratio was kept constant at 0.5, and the sand/binder ratio was 3. Workability, dry unit weight, water absorption ratio and porosity, flexural strength, compressive strength, abrasion, carbonation, and high-temperature resistance tests were performed on the mortar specimens. Based on the results of laboratory work, it was observed that the replacement of CKD with cement reduces the workability of fresh mortar. Compressive and flexural strengths of CKD-added mixtures were found to be equivalent or insignificantly lower than that of the control sample. The addition of CKD had a negligible effect on water absorption and porosity of samples. Besides, the residual compressive strength determined after the elevated temperature test for the sample made with CKD were found to be equivalent or higher compared to the control sample. Present laboratory studies showed that utilization of CKD in cementitious mortar system is feasible in terms of testing conducted.Book Part Citation - Scopus: 2Properties of Alkali-Activated Lightweight Concrete(Elsevier, 2022) Top, S.; Altiner, Mahmut; Vapur, HüseyinThis chapter presents a brief overview of the properties of alkali-activated lightweight concrete. Nowadays, the production of lightweight concrete has great attentions due to its extraordinary advantages such as reduced mass, improved sound and thermal insulation properties. Furthermore, the low gas emissions and the utilization of waste materials increase the importance of alkali-activated lightweight concrete. In this chapter, the strengths of lightweight concrete were examined by considering the aggregate type and density, the alkali activator type and concentration, the type of fiber reinforcements and foaming agents, which are the factors that have the most impact on the strengths. Thermal conductivity, fire resistance, acoustic performance, and durability properties have been explained considering the key points in the literature. In addition to porosity, it has been determined that one of the most important factors directly affecting the fire resistance is the precursor type. It has been concluded that the fire resistance of the concrete prepared by using K-based precursors is higher. Acoustic performances of alkali-activated lightweight concrete vary. It is necessary to use a high amount of aggregate in order to obtain concretes with wide frequency ranges and high absorption coefficient. Contrary to concrete produced from Portland cement, alkali-activated concrete is more resistant to acid and sulfate attacks, since the formation of gypsum and strength is less. © 2022 Elsevier B.V., All rights reserved.Conference Object Citation - Scopus: 1On the Variation in Several Rock Properties due to Magnesium Sulfate Weathering Tests ‒ A Case Study for Limestones(International Multidisciplinary Scientific Geoconference, 2019-06-20) Köken, E.Contributions to the behavior of rock materials under various conditions provide a practical knowledge about issues relating the performance and long-term serviceability of rocks. In this study, various limestones with varying textural features were investigated in terms of their resistance against magnesium sulfate weathering tests. For this purpose, initial physico-mechanical properties of limestones were determined. Then, rock materials were subjected to magnesium sulfate weathering tests (up to 20 cycles) and the variation in physico-mechanical properties were determined for each rock type. As a result of laboratory tests, compared to initial rock properties, effective porosity (ne, %) increased in the range of 3% ‒ 14% and 12% ‒ 35% after 10th and 20th magnesium sulfate weathering cycles, respectively. Uniaxial compressive strength of rocks (UCS, MPa) decreased by 9% ‒ 24% after 10th cycles and by 32% – 58% after 20th cycles. Brazilian tensile strength of rocks (BTS, MPa) decreased in the range of 7% ‒ 19% and 20% ‒ 49% after 10th and 20th cycles, respectively. Similar to the variations in UCS and BTS, Tangential Young Modulus (Eti, GPa) also decreased at a rate of 13% ‒ 28% and 23% ‒ 64% after 10th and 20th cycles, respectively. However, the values of Tangential Poisson’s Ratio (vti) fluctuated with progressive accelerated weathering cycles, which could be linked to varying axial and lateral strain rates at 50% of UCS values for the limestones investigated. Furthermore, the variation in crack initiation stress σCI (MPa) due to progressive magnesium sulfate tests were also evaluated considering two strain-based methods and the findings showed that σCI of limestones slowly decreased with increasing weathering test cycles. It could be claimed that cyclic magnesium sulfate tests performed on rock materials would be beneficial for assessing the long-term serviceability of rocks. In this context, mud-supported limestones seem to have a greater resistance against magnesium sulfate weathering tests compared to the grain-supported ones. However, the number of samples should be increased in order to achieve a comprehensive understanding about the degradation processes of limestones. © 2021 Elsevier B.V., All rights reserved.Article Citation - WoS: 9Citation - Scopus: 11Evaluation of Diatomite Substitute With Thermal Power Plant Waste Fly Ash in Sustainable Geopolymer Through Life Cycle Assessment(Springer, 2025-02-28) Ilkentapar, Serhan; Orklemez, Ezgi; Durak, Ugur; Gulcimen, Sedat; Bayram, Savas; Uzal, Nigmet; Atis, Cengiz DuranThis research demonstrates the potential of diatomite as a fly ash replacement to improve mechanical properties and environmental sustainability and presents it as a viable alternative for sustainable construction. Additionally, a life cycle assessment (LCA) was conducted on the produced mortars to quantitatively compare their environmental impacts using a cradle-to-gate approach. In mixtures, it was used by replacing the diatomite in the ratios of 1%, 2%, 3%, 4%, and 5% by weight of the fly ash. Workability, unit weight, flexural and compressive strength, abrasion resistance, elevated temperature resistance and microstructure analysis were carried out. The results indicated that replacing 1%, 2%, and 3% diatomite increased the compressive and flexural strength of mortars due to their higher specific surface area. Two percent replacement of diatomite provided the best results. FESEM results of 3% diatomite inclusion showed more intense and compact microstructure of geopolymer. Diatomite inclusion increased the abrasion resistance of geopolymer. Since 2% diatomite replacement was found to be optimum, the LCA results showed that geopolymer mortar with 2% diatomite has 25% lower impacts in terms of global warming potential and 10% lower impacts in terms of terrestrial ecotoxicity than conventional Portland cement mortar.Article Citation - WoS: 8Citation - Scopus: 10Compatibility and Biomineralization Oriented Optimization of Nutrient Content in Nitrate-Reducing Microbial Self-Healing Concrete(MDPI, 2021-08-11) Kardogan, Beyza; Sekercioglu, Kadir; Ersan, Yusuf CagatayMicrobially induced calcium carbonate precipitation (MICP) can be mentioned among the popular approaches to develop a self-healing concrete. The production of dissolved inorganic carbon through microbial activity is the main precursor for MICP in concrete and it is limited by the bioavailability of the nutrients. When nutrients are added to the mortar as admixtures, their bioavailability becomes more significant for crack repair because nutrients disperse in the mortar and considerable fraction stays far from a single crack. Therefore, the determination of bioavailability of nutrients and its variation with the initial nutrient content and crack age is essential to optimize a recipe for bacteria-based self-healing concrete. This study presents the optimum nutrient content defined for nitrate-reduction-based self-healing bioconcrete. In the tests, calcium nitrate (CN) and calcium formate (CF) were combined with a CF:CN w/w ratio of 2.50. Mortar properties and bioavailability of nutrients were analysed at different nutrient doses. Moreover, the bioavailability of nutrients at different crack ages changing between 3 and 56 days was monitored. Finally, resuscitation, microbial activity and the MICP performance of nitrate reducing biogranules were tested at defined nutrient bioavailabilties. The optimum nutrient content was determined as 7.00% (CF 5.00% and CN 2.00%). The leaching rates of formate ions were twice the leaching rate of the nitrate ions at similar initial concentrations, which led to a bioavailable HCOO-/NO3-N ratio of 23 g/g in cracked mortar. Under optimum nutrient conditions, the CaCO3 precipitation yield of nitrate reducing biogranules was recorded as 1.5 g CaCO3/g HCOO- which corresponded to 68% C precipitation efficiency.Article Citation - Scopus: 2Comparison of Mechanical and Physical Properties of Screed With and Without Expanded Polystyrene (EPS) Particles(Yildiz Technical University, 2022-12-31) Kiliç, Fikret Merih; Yorulmaz, Hediye; Özuzun, Sümeyye; Durak, Uğur; İLkentapar, Serhan; Karahan, Okan; Atis, C. D.In this study, in order to observe the mechanical and physical properties of ordinary screed, sandy-lightweight screed and lightweight screed samples, expanded polystyrene (EPS) was used as fine aggregate and lightweight screed systems were produced by replacing sand at 100%, 50% and 0%. Samples of cement dosages of 250, 300, 350 kg/m3 were produced for lightweight screeds, sandy-lightweight screeds and ordinary screeds. Unit weight, water absorption capacity, flexural strength, compressive strength, fire resistance, abrasion and thermal conductivity tests were performed on the produced screed systems. As a result of the research, it was determined that as EPS ratio increases in screed system; unit weights decreased, water absorption rates increased. Besides, the flexural and compressive strengths, fire and abrasion resistance are also decreased. However, it was observed that the thermal conductivity coefficient reduced with the increment of EPS particles in the screed. In normal, sandy-lightweight and lightweight screeds, it was determined that as the cement dosage increased; the unit weights, flexural and compressive strengths, fire and abrasion resistance increased, water absorption capacity and the thermal conductivity coefficient decreased. © 2022 Elsevier B.V., All rights reserved.Article Citation - WoS: 4Citation - Scopus: 4Characterization of Limestone Calcined Clay Cement Made With Calcium Sulfoaluminate Clinker(Springer int Publ Ag, 2024-07-02) Atasever, Muhammet; Erdogan, Sinan TurhanThis study concentrated on producing limestone calcined clay calcium sulfoaluminate cement by replacing portland cement in limestone calcined clay cement with calcium sulfoaluminate cement, with the goal of increasing the early strength of limestone calcined clay cement. The mineralogy and microstructures of hydrating pastes were investigated using x-ray diffraction and scanning electron microscopy. Heat evolution was studied using isothermal calorimetry. Strength development and workability were assessed on mortar samples. The 1 day strengths of limestone calcined clay calcium sulfoaluminate cement samples exceeded those of limestone calcined clay cement by similar to 30-80%, though its strength gain slows significantly after 1 day due to the lack of calcium silicates, affecting pH and clay dissolution. Despite this, the strength development of limestone calcined clay calcium sulfoaluminate cement, when adjusted for CO2 emissions, is comparable to limestone calcined clay cement. Additionally, limestone calcined clay calcium sulfoaluminate cement provides a 10-15% higher flow and exhibits a lower heat of hydration beyond 12 h, while maintaining a production cost similar to that of limestone calcined clay cement.Article Citation - WoS: 8Citation - Scopus: 9A New Quantitative Welding Degree Classification for Ignimbrites(Springer, 2023-06-28) Akin, Mutluhan; Topal, Tamer; Dincer, Ismail; Akin, Muge K.; Ozvan, Ali; Orhan, Ahmet; Orhan, AyseAs a pyroclastic rock type, ignimbrites may reveal varying degrees of welding depending on the temperature (> 535 celcius) and overburden pressure conditions during its formation. The welding degree of ignimbrites increases as the formation temperature and the thickness of the overburden deposit in the depositional environment escalate, which are the most crucial factors controlling the rate of welding in ignimbrites. With the increasing temperature, plastic deformation is observed in ignimbrites and the glassy minerals are being welded. Furthermore, the thickness of the overburden causes the deformation of the ash matrix in ignimbrites at the lower sections and the pumice grains are flattened at different rates. An increase in the degree of welding of ignimbrites causes an improvement in the physical and mechanical properties of the rock material as well. Within the scope of this research, petrographical, mineralogical, and geochemical studies were carried out on a total of 16 different ignimbrite types, which have different color and texture properties, obtained from three different regions of Turkey (Kayseri, Nevsehir, Ahlat) where ignimbrites extensively crop out, and the physical and mechanical properties of these samples were revealed. Consequently, a new welding classification was developed for ignimbrites considering the uniaxial compressive strength and dry unit weight. The proposed welding classification consists of six classes ranging from non-welded to highly welded. When the welding degrees of the selected ignimbrites are evaluated, Kayseri ignimbrites mostly exhibit moderate welding characteristics. Nevsehir ignimbrites, on the other hand, have a low welding degree whereas the degree of welding in Ahlat ignimbrites may vary from low to high. Additionally, long and short axis lengths of pumice grains in the ignimbrite specimens were determined by measuring under the microscope, and shape ratios were determined by different shape parameter evaluation methods. As a result, it has been concluded that the pumice grains in Kayseri and Ahlat ignimbrites have a more lenticular structure than the pumice grains in Nevsehir ignimbrites. Eventually, the welding degree classes of ignimbrites and the classification developed by using threshold values of the oblateness ratio (OR) values of pumice grains at different welding degrees are quite compatible. The proposed welding degree classification is of great importance in the selection of ignimbrites widely used as dimension stone and in terms of engineering classification of this rock type as well as it will guide to the scientific studies to be performed on ignimbrites with varying physical and mechanical properties.