Civil Engineering / İnşaat Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/13
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Article Citation - WoS: 7Citation - Scopus: 8Enrichment of Trace Element Concentrations in Coal and Its Combustion Residues and Their Potential Environmental and Human Health Impact: Can Coal Basin, Nw Turkey as a Case Study(Inderscience Enterprises, 2016) Baba, Alper; Gürdal, Gülbin; Şanlıyüksel Yücel, DenizIn this study, the variation of trace element concentrations ( total of 48 trace elements including rare earth elements) in coal, coal ash and fly ash were examined and compared with coal Clarke values. Results showed that the average concentrations of trace elements including As, B, Cu, Ce, Co, Cs, Gd, Hf, La, Lu, Mo, Nd, Nb, Pr, Pb, Sc, Sm, Ta, Tb, Th, U, V, W, Y, Yb, Zn and Zr in the Can Basin coals are higher than their respective Clarke values for world low-rank coals. The elements As, Cu, Co, Cs, Mo, Nb, Sc, Pb, Pr, Th, U, V, Zn and Zr are enriched in coal ashes, whereas As, Co, Nb, Sc, U and V are enriched in fly ashes. Among the elements, maximum enrichment in coal was observed for As, with the average concentration of 253.5 ppm As in the Can Basin coals, while the coal Clarke value is 14 ppm and world average value is 8.3 ppm. From the ecotoxicological point of view, combustion residues formed by indoor combustion of coal and/or in thermal power plants may be a hazard to the environment and to aquatic and terrestrial life including human beings, particularly As, trace elements and released radioactive elements.Article Citation - WoS: 1Citation - Scopus: 1Generalized Regression Neural Network and Empirical Models To Predict the Strength of Gypsum Pastes Containing Fly Ash and Blast Furnace Slag(Springer Verlag, 2020) Erdem, Tahir Kemal; Cengiz, Okan; Tayfur, GökmenGypsum is widely used in constructions owing to its easy application, zero shrinkage, and excellent fire resistance. Several parameters can affect the properties of gypsum pastes. To study the strength of the gypsum pastes experimentally by trying all these parameters is time-consuming and costly. Therefore, artificial intelligence methods can be very useful to predict the paste strength, which, in turn, can reduce the number of trial batches. Based on experimental data, the generalized regression neural network (GRNN) and empirical models were developed to predict strength of gypsum pastes containing fly ash (FA) and blast furnace slag (BFS). Gypsum content, pozzolan content, curing temperature, curing duration, and testing age constituted the input variables of the models while the paste strength was the target output. The trained and tested GRNN model was found to be successful in predicting strength. Sensitivity analysis by the GRNN model revealed that the curing duration and temperature were important sensitive parameters. In addition to the GRNN model, empirical models were proposed for the strength prediction. The same input variables formed the input vectors of the empirical models. The same dataset used for the calibration of the GRNN model was employed to establish the empirical models by employing genetic algorithm (GA) method. The empirical models were successfully validated. The GRNN and GA_based empirical models were also tested against the multi-linear regression (MLR) and multi-nonlinear regression (MNLR) models. The results showed the outperformance of the GRNN and the GA_based empirical models over the others.Article Citation - WoS: 5Citation - Scopus: 7Experimental and Modeling Study of Strength of High Strength Concrete Containing Binary and Ternary Binders(Foundation Cement, Lime, Concrete, 2011) Erdem, Tahir Kemal; Tayfur, Gökmen; Kırca, ÖnderSilica fume (SF), fl y ash (FA) and ground granulated blastfurnace slag (S) are among the most widely utilized mineral additions for normal strength concrete (NSC) and high strength concrete (HSC). High Reactivity Metakaolin (HRMK) is a relatively new mineral addition, produced by calcination of highly pure kaolin. The replacement of cement with HRMK increases the strength, especially at early ages, and improves durability of concrete. (1-3). Pumice (P) is a porous volcanic glass containing 60-75 SiO2% and 13-17% Al2O3. When fi nely ground, it shows pozzolanic characteristics but it is generally used as a lightweight aggregate in the concrete industry (4, 5). HRMK and P have white color and, therefore, are useful for production of white concrete when applied with white Portland cement (WPC)Article Citation - WoS: 47Citation - Scopus: 53Effect of Sustained Flexural Loading on Self-Healing of Engineered Cementitious Composites(Japan Concrete Institute, 2013) Özbay, Erdogan; Şahmaran, Mustafa; Yücel, Hasan Erhan; Erdem, Tahir Kemal; Lachemi, Mohamed; Li, Victor C.This paper aims to clarify the effects of sustained flexural loading on the self-healing behavior of Engineered Cementitious Composites (ECC). Prismatic specimens of ECC mixtures with two different levels of Class-F fly ash content were cast. Flexural loading was applied to the specimens at 28 days age to generate severe amount of microcracks. The specimens were then stored under continuous water or air exposures with or without sustained mechanical loading, for up to 90 days. For specimens under sustained mechanical loading, the applied sustained load level was 60% of the ultimate flexural strength. The extent of damage was determined as a percentage of loss in mechanical properties. The influences of different exposure regimes and sustained mechanical loading on mechanical properties of ECC mixtures were investigated. Microstructural changes within the microcracks were also analyzed.Article Citation - WoS: 75Citation - Scopus: 87Use of Spent Foundry Sand and Fly Ash for the Development of Green Self-Consolidating Concrete(Springer Verlag, 2011) Şahmaran, Mustafa; Lachemi, Mohamed; Erdem, Tahir Kemal; Yücel, Hasan ErhanIn the United States alone, the foundry industry discards up to 10 million tons of sand each year, offering up a plentiful potential resource to replace sand in concrete products. However, because the use of spent foundry sand (SFS) is currently very limited in the concrete industry, this study investigates whether SFS can successfully be used as a sand replacement material in cost-effective, green, self-consolidating concrete (SCC). In the study, SCC mixtures were developed to be even more inexpensive and environmentally friendly by incorporating Portland cement with fly ash (FA). Tests done on SCC mixtures to determine fresh properties (slump flow diameter, slump flow time, V-funnel flow time, yield stress, and relative viscosity), compressive strength, drying shrinkage and transport properties (rapid chloride permeability and volume of permeable pores) show that replacing up to 100% of sand with SFS and up to 70% Portland cement with FA enables the manufacture of green, lower cost SCC mixtures with proper fresh, mechanical and durability properties. The beneficial effects of FA compensate for some possible detrimental effects of SFS.Article Citation - WoS: 61Citation - Scopus: 69Leaching Characteristics of Fly Ash From Fluidized Bed Combustion Thermal Power Plant: Case Study: Çan (çanakkale-Turkey)(Elsevier Ltd., 2010) Baba, Alper; Gürdal, Gülbin; Şengünalp, FatmaIt is known that the concentration of elements of fly ash varies due to the used-coal and the used-lime qualities varying in different periods. In the Çan Thermal Power Plant (CTPP) located at northwestern Turkey, Çan (Çanakkale) basin coals, which are classified as lignite to sub-bituminous C coal with high total sulphur (0.4-12.22%) and a broad range of ash contents (3.2-44.6%) are mainly used. Performed studies reveal that some toxic elements exit in the coal, including As, U and V. Also, while the As, Cu, Co and Hg contents in coal increases, the sulphur contents in coal also increase. Additionally, trace elements that have inorganic compounds in coal are mobilized into air during the combustion process. This poses a big risk for human health and keeping the environment when Çan Basins low quality lignite is burned, it's the fly ash that contains several toxic elements which can leach out and contaminate the water resources. In this study, toxicity tests were conducted on the fly ash samples that were obtained from the fluidized bed combustion of Çan Thermal Power Plant. The results showed that water temperature, pH and the quality of the limestone used were the most important factors affecting the leaching properties. Concentration of some toxic elements found in the fly ash, such as; As, Cd, Cr, Pb, Se and Zn were analyzed. Concentration richness of some heavy metals were attributed to the increase of water temperature, especially when pH is lower than 5. At pH=5 value, there is no clear explanation of each heavy metal presence in the fly ash from fluidized bed combustion thermal power plant. © 2010 Elsevier B.V. All rights reserved.