1,720,986 research outputs found
Characterization of trace elements and radionuclides and their risk assessment in red mud
No full textRed mud is a waste and tail material from primary aluminum production, and is named for its color, coming from its iron oxide content. The quantity of red mud is almost equal to the primary aluminum production and leads to a considerable environmental issue. Red mud of the ETI Seydisehir Aluminum Plant is considered as detrimental waste for storage due to its content of various metal oxides, elements and caustics. This detrimental effect is classified into two groups: first, environmental health and second, the cost of storage. In order to minimize the negative effect of red mud, there have been or are presently many investigations carried out on usage of red mud in building materials. However, no effective way of utilizing red mud has yet been found. in this study domestic red mud was investigated and chemical analyses were performed by EDAX and XRF techniques. Radioactivity of the samples was also measured with gamma spectroscopy. The concentrations of elemental Na, Al, Si, Ca, Ti, Fe, S and K were determined by EDAX and XRF. In addition, Cr, Zr, Sr, Ni and Y were also identified as impurities. According to gamma spectroscopy results radium, uranium, thorium and potassium were determined as radioactive elements. It was observed that the amounts of the radioactive elements present in the red mud are within safe limits. Therefore, if domestic red mud originated from Seydisehir could be utilized as reinforcement material in composites, and in building materials, it can be considered safe in terms of environmental and human health. (c) 2007 Elsevier Inc. All rights reserved
Electrical resistivity of porcelain bodies with natural zeolite addition
No full textIn this study, the effect of natural zeolite addition on the electrical properties of porcelain bodies was investigated. Clinoptilolite, which is a type of natural zeolite, was added partially or fully in replacement of quartz in selected electro-porcelain compositions. Samples were fired in an electric furnace with a heating rate of 10 degrees C/min at 1200 and 1250 degrees C with a period of 60 min. The electrical resistance measurements of samples were performed at 50, 200, 400 and 600 degrees C. It was shown that the resistivity of samples increased at 50 degrees C temperature after zeolite addition, while it was decreasing after zeolite addition at higher temperatures. At the same time, it was recognized that the resistivity of samples depends on sintering temperature. The activation energy of electrical resistivity of samples was found to be in the range of 0.79-0.87 eV. (C) 2009 Elsevier Ltd and Techna Group S.r.l. All rights reserved
Sustainability for Blast Furnace Slag: Use of Some Construction Wastes
No full textBlast furnace slag is a by-product from blast furnaces which is used to produce iron. Blast furnace slag has been used extensively as a successful replacement material for Portland cement in concrete materials to improve durability, produce high strength and high performance concrete, and brings environmental and economic benefits together, such as resource conservation and energy savings. Construction wastes define as relatively clean and heterogeneous building materials which are generated from various construction activities. Among them, ceramic, brick, and marble wastes can be included. These kinds of wastes can be used successfully as replacement materials in the cement mortar or concrete mixing. The use of alternative aggregate is a natural step towards solving part of the depletion of natural aggregate, and the alternative aggregate processed from waste materials which would appear to be an even more sensible solution. Recycled aggregates, such as ceramic, brick, and marble wastes, in the blast furnace slag concrete have been investigated in the limited number of studies to date. In the literature, use of these wastes in the concrete produced by blast furnace slag, as replacement materials in cement have not found adequate attention. Therefore, in the present study, the effects of ceramic, brick, and marble wastes used as fine/coarse aggregates on the properties of blast furnace slag investigated. Thus, the contribution of these wastes on the sustainability of blast furnace slag concrete was presented in a detailed manner. Consequently, construction waste aggregates and blast furnace slag can be used to improve the mechanical properties, workability, and chemical resistance of the conventional concrete mixtures. Since the construction waste and blast furnace slag wastes are available in vast amounts in Turkey, it is economically and environmentally suitable to use these materials as aggregates in the production of more durable concrete mixtures. (C) 2015 Published by Elsevier Ltd
Properties of Hardened Concrete Produced by Waste Marble Powder
No full textMarble is industrially processed by being cut, polished, and used for decorative purposes, and thus, economically valuable. In marble quarries, stones are cut as blocks through different methods. During the cutting process, 20-30% of a marble block becomes waste marble powder. Marble powder is a waste material generated in considerable amounts in the world. Marble waste leads to a serious environmental problem as well. Therefore, the use of waste marble in the concrete production as an admixture material or aggregate has increasingly become an important issue. In the present study, effect of different usage areas of waste marble on the hardened concrete properties was investigated based on previous studies. In this context, (1) compressive, flexural, and splitting tensile strength, (2) modulus of elasticity, (3) ultrasonic pulse velocity, (4) Schmidt surface hardness, and lastly (5) sorptivity coefficient/porosity of the hardened concrete, were examined. Comparing all results, the proposition the marble waste can be used in the production of concrete was discussed in a detailed manner. As a result, the use of waste marble powder in (1) conventional concrete mix, (2) self-compacting concrete mix, and (3) polymer concrete mix, was revealed. Consequently, it was found out that the use of waste marble in the conventional concrete mix as an admixture material or aggregate is suitable as it can improve some properties of the hardened concrete. However, the use of waste marble in the self-compacting and polymer concrete mixes as an admixture material or aggregate is not affected positively in terms of hardened properties of concrete. (C) 2015 Published by Elsevier Ltd
Coating properties of 1H,1H-perfluorooctylamine-terminated polyimides based on hexafluoroisopropylidene diphthalic anhydride and 1,4,5,8 naphthalenetetracarboxylic dianhydride
No full textThis study attempted to prepare polyimide coatings (PIs) containing 6FDA (hexafluoroisopropylidene diphthalic anhydride) and/or NTDA (1,4,5,8 naphthalenetetracarboxylic dianhydride) in various ratios. 1% of these polyimide chains were terminated with 1H,1H-perfluorooctylamine (PFOA) and PFOA, and terminated polyimide coatings (PIFs) were prepared in the same ratios as PIs. Coatings were produced on aluminum substrates by a 75-mu m wire-wound applicator and thermally imidized. Finally, thermal, wear, and physical properties of PIFs and PIs were compared to each other. PIFs exhibited higher abrasion resistance than PIs due to the presence of PFOA. The increase in 6FDA content also resulted in elevated abrasion resistance. Both NTDA and 6FDA compounds improved thermal stability. The increase in NTDA content raised the T-g values of the polyimides. PIFs exhibited higher static water contact angle values than PIs, but the existence of microcracks decreased their hydrophobicity. The gloss values of PIFs were excellent. Improved values were obtained for pencil hardness, crosscut adhesion, and MEK (methyl ethyl ketone) rubbing properties for all coatings. In addition to the pencil hardness test, a pendulum hardness test was also carried out. The presence of PFOA affected pendulum hardness values positively, and the increase in the amount of 6FDA on polymer backbone improved the pendulum hardness values despite the rigidity of NTDA
Durability Properties of Concrete Produced by Marble Waste as Aggregate or Mineral Additives
No full textIn recent years, the growth in the industrial production and the consequent increase in the corresponding consumption have led to a fast decline in available natural resources. However, a high volume of the industrial production has generated a considerable amount of waste materials which have a number of adverse impacts on the environment. In this regard, the marble industry produces a huge amount of waste in the last decades and grows significantly in time. The marble waste is generally a highly polluting type of industrial wastes due to its highly alkaline nature and its manufacturing and processing techniques, all of which impose serious health threats to the surroundings. In this study, effects of waste marble on some durability properties such as water absorption and permeability, chloride penetration and carbonation, sulphate attack and abrasion resistance, and lastly performance at high temperature and freezing and thawing cycles of conventional or self-compacting concrete were investigated. As a result, it was found out that the use of waste marble in the conventional or self-compacting concrete mix as an admixture material or aggregate is suitable as it can improve durability properties of the concrete. Especially, properties of water absorption & permeability and resistance of chloride penetration & sulphate attack were improved by incorporation of waste marble in concrete. (C) 2016 The Authors. Published by Elsevier Ltd
Effect of Subsequent Aging in SiC P Reinforced AA2124 Aluminum Metal Matrix Composite
No full textThe present study is focused on the evaluation of the aging behaviour and microstructure characterization of AA2124/SiC/25p composite under the aging temperatures of 180, 185 and 190 °C for various dwelling time ranging from 0 up to 100 hours. The microstructure was characterized by means of scanning electron microscopy. The hardness, energy dispersive spectroscopy analysis and X-ray diffraction measurements were also performed to evaluate the characteristics of aged AA2124/SiC/25p composite. The results show that the hardness values of as-received composite were considerably improved up to two third by the subsequent aging. The hardness increasing was attributed to the presence of CuAl 2 , Al 4 SiC 4 and precipitation phases in aged AA2124/SiC/25p composite
Effect of natural zeolite addition on sintering kinetics of porcelain bodies
Get PDFThe aim of this study was to investigate the effect of natural zeolite addition on the sintering kinetics. Clinoptilolite which is a type of natural zeolite was added partially or fully in replacement of quartz at selected electro-porcelain composition. Samples were fired in an electric furnace with a heating rate of 10 degrees C/min at 1150, 1200 and 1250 degrees C with a period of 5, 10, 20, 30, 60 and 90 min. The sintered samples were characterized by XRD and SEM. Sintering activation energies were determined according to the bulk density results. It was found that the sintering activation energy decreased with increasing zeolite addition. (C) 2007 Elsevier B.V. All rights reserved
Waste to shield: Tailoring cordierite/mullite/zircon composites for radiation protection through controlled sintering and Y2O3 addition
No full textIn this study, investment casting shell waste successfully utilized to produce cordierite/mullite/zircon composites. Green pellets, consisting of investment casting shell waste, alumina, and magnesia, were prepared and sintered at temperatures between 1250 and 1350 °C. The influence of the sintering temperature on the crystalline phase composition, densification behavior, flexural strength, microstructure, and radiation shielding properties of the cordierite/mullite/zircon composites is investigated. Phase analysis showed that characteristic cordierite peaks appear at 1250 °C, but the complete conversation of silica from investment casting shell waste into cordierite requires a sintering temperature of at least 1300 °C. Notably, the cordierite/mullite/zircon composite sintered at 1350 °C exhibited a sixfold increase in flexural strength compared to the ceramic composite directly fabricated from investment casting shell waste at the same sintering temperature. Furthermore, the effect of Y2O3 addition on composites\" radiation shielding properties is investigated. The results show that the Y2O3 addition improves densification behavior, enhancing the shielding capabilities of the composites against fast neutron and gamma radiation. Our findings suggest that the developed ceramic composites show significant potential for gamma-ray and neutron shielding applications
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