摘要 :
Turkey has the world's largest boron reserves. Colemanite is one of these minerals. A large amount of waste is produced during the production of boric acid from colemanite. In this study, usability of boron wastes (BW, borogypsum)...
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Turkey has the world's largest boron reserves. Colemanite is one of these minerals. A large amount of waste is produced during the production of boric acid from colemanite. In this study, usability of boron wastes (BW, borogypsum) and barite as a radiation shielding materials was investigated. Six compositions were shaped with various ratios of borogypsum and barite. After drying, shaped samples were sintered at 1050 degrees C. Sintered samples were evaluated for density, water absorption, porosity and gamma ray radiation shielding. The best attenuation coefficients were 0.225678, 0.148848 and 0.142652 cm(-1) at 662, 1173 and 1332 keV photon energies, respectively.
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Gypsum is a dihydrated calcium sulfate, with the composition of CaSO4 center dot 2H(2)O, with large application interest in ceramic industry, odontology, sulfuric acid production, cement, paints, etc. During calcination, a phase t...
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Gypsum is a dihydrated calcium sulfate, with the composition of CaSO4 center dot 2H(2)O, with large application interest in ceramic industry, odontology, sulfuric acid production, cement, paints, etc. During calcination, a phase transformation is observed associated to the loss of water, leading to the formation of gypsum or anhydrite, which may present different phases. The identification of the phases is not so easy since their infrared spectra and their X-ray diffraction patterns are quite similar. Thus, in this work, temperature modulated differential scanning calorimetry (TMDSC) was used to identify the different gypsum phases, which can be recognized by their different profiles.
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In this study, the influences of air-entraining, set accelerating and superplasticizer admixtures on the properties of borogypsum containing cement mortars were investigated. According to results, by using 3% borogypsum and water/...
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In this study, the influences of air-entraining, set accelerating and superplasticizer admixtures on the properties of borogypsum containing cement mortars were investigated. According to results, by using 3% borogypsum and water/binder ratio of 0.45, the compressive and flexural strength values were increased up to 196.38%. The usage of various ratios of air-entraining and set accelerating admixtures showed reverse effects on the compressive and flexural strength. However, 0.4% superplasticizer containing mortars had 65.39MPa compressive strength and 9.08MPa flexural strength which were 33.12% and 26.82% higher than the reference. Durability test results showed addition 3% borogypsum provided endurance to sulfate attacks up to 30 days.
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摘要 :
In Turkey, a large amount of borogypsum waste is discharged by the economically important boric acid industry. Calcination of this waste provides a promising technique not only for recovering an economic value but also for reducin...
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In Turkey, a large amount of borogypsum waste is discharged by the economically important boric acid industry. Calcination of this waste provides a promising technique not only for recovering an economic value but also for reducing its environmental impact. The aim of this work is to study the thermal behavior of borogypsum, which contains gypsum crystals, boron oxide and some impurities under nonisothermal conditions in air atmosphere by using thermogravimetry and differential thermal analysis techniques (TG-DTA). Experiments were carried out at temperatures ranging from ambient to 773 K at different heating rates. The temperatures of conversion from gypsum to hemihydrate and anhydrite states were determined. Various methods were used to analyze the TG and DTA data for determination of reaction kinetics. The activation energy and frequency factor were calculated for dehydration of borogypsum. Activation energy values of the main dehydration reaction of borogypsum were calculated to be approximately 95-114 kJ mol~(-1).
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A number of studies have been conducted recently to investigate the influence of randomly oriented fibers on some engineering properties of cohesive and cohesionless soils. However, few studies have been carried out on fine-graine...
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A number of studies have been conducted recently to investigate the influence of randomly oriented fibers on some engineering properties of cohesive and cohesionless soils. However, few studies have been carried out on fine-grained soils modified with discrete fiber inclusions and additive materials. This experimental study was performed to investigate the effect of randomly distributed Polypropylene fibers (PP) and some additive materials [e.g., Borogypsum (BG), Fly Ash (FA) and Cement (C)] on unconfined compressive strength of a fine-grained soil cured for 7,14 and 28 days. The Taguchi method was applied to the experiments and a standard L9 Orthogonal Array (OA) with four factors and three levels were chosen. A series of unconfined compression tests (7,14 and 28 days) were conducted on each specimen. 0-20% BG, 0-20% FA, 0-0.25% PP and 0-3% of C by total dry weight of mixture were used in the preparation of specimens. Experimental results showed that the most effective material for increasing the unconfined compressive strength of the samples was poly propylene fiber. The values of unconfined compressive strength for curing times of 7, 14 and 28 days in optimum conditions were 0.94 MPa, 1.25 MPa and 1.95 MPa, respectively.
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This work presents some results of studying the effect of ultrasonic treatment on the kinetics of the formation of calcium hydrosilicate from boron-containing mineral feedstock processing wastes, namely, borogypsum. Kinetic parame...
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This work presents some results of studying the effect of ultrasonic treatment on the kinetics of the formation of calcium hydrosilicate from boron-containing mineral feedstock processing wastes, namely, borogypsum. Kinetic parameters and rate constants were determined for the synthesis reactions of calcium hydrosilicate from borogypsum under ultrasonic treatment conditions and conventional stirring.
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The present work describes a study of setting and hardening of blends of borogypsum, fly ash, and Portland cement clinker (PC). The possibility of using borogypsum instead of natural gypsum in fly ash-cement matrix has been invest...
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The present work describes a study of setting and hardening of blends of borogypsum, fly ash, and Portland cement clinker (PC). The possibility of using borogypsum instead of natural gypsum in fly ash-cement matrix has been investigated through several tests. In addition, the effects of molasses on the setting times of cement and strength of the mortar were also studied. The setting times of the cement were retarded when the natural gypsum was replaced by borogypsum. Molasses exhibited a rather significant retarding effect when used in combination with borogypsum in cement. The inclusion of molasses to the system at a level of 0.1 percent resulted in a reduction in early strength of the mortar. However, it significantly enhanced the strength of the mortar after 7 days of curing age. In general, the cement prepared with borogypsum was found to have similar strength properties to those obtained with natural gypsum, and inclusion of molasses into the system significantly increased the strength of the sample after 7 days of curing age.
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摘要 :
Borogypsum, formed during the production of boric acid, is discharged improperly or dumped into privately constructed dams, which contributes to environmental pollution. On the other hand, production of fertilizers containing bori...
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Borogypsum, formed during the production of boric acid, is discharged improperly or dumped into privately constructed dams, which contributes to environmental pollution. On the other hand, production of fertilizers containing boric acid and boron is an expensive process. The utilization of the waste borogypsum in the production of boron-containing fertilizers was investigated in this study. Fertilizers obtained from wastes are highly beneficial for the environment, and additionally, they contain phosphorus, nitrogen, sulfur, calcium, and boron. Thus, industrial scale production of boron-containing fertilizers from borogypsum is an economically novel and environmental-friendly approach. This study aims at investigating the possible utilization of borogypsum for triple superphosphate production at the laboratory scale. The results of the study illustrate that it is possible to use waste borogypsum for production of triple superphosphate in a continuous-flow process. Thus, utilization of borogypsum is not only an alternative process but also allows the protection of the environment from fluorine and borogypsum wastes.
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摘要 :
Boron ores are used in the production of various boron compounds such as boric acid, borax and boron oxide, boric acid is produced by reacting colemanite (2CaO centre dot 3B_2O_3 centre dot 5H_2O) with sulphuric acid and a large q...
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Boron ores are used in the production of various boron compounds such as boric acid, borax and boron oxide, boric acid is produced by reacting colemanite (2CaO centre dot 3B_2O_3 centre dot 5H_2O) with sulphuric acid and a large quantity of borogypsum is formed during this production. This waste causes various environmental problems when discharged directly to the environment. Portland cement is the most important material in the building industry. This material is produced by adding about 3-5 percent gypsum (CaSO_4 centre dot 2H_2O) to clinker as a set retarder. The aim of this study was to stabilize borogypsum, and to produce cements by adding borogypsum instead of natural gypsum to clinker. Concrete using cement produced with borogypsum was tested to find the mechanical properties and the test values were compared with compared with those of concrete from cement with natural gypsum. Compressive strength of concrete from cement produced with borogypsum was found to be higher than that of natural gypsum. Also, the setting time of cement with borogypsum was longer than that of the Portland cement.
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Thermal dehydration of gypsum and borogypsum was investigated under nonisothermal conditions in air by using simultaneous thermogravimetric-differential thermal analyzer. Nonisothermal experiments were carried out at various linea...
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Thermal dehydration of gypsum and borogypsum was investigated under nonisothermal conditions in air by using simultaneous thermogravimetric-differential thermal analyzer. Nonisothermal experiments were carried out at various linear heating rates. Kinetics of dehydration in the temperature range of 373―503 K were evaluated from the DTA (differential thermal analysis)-TGA (thermogravimetric analysis) data by means of Coats-Redfern, Kissinger and Doyle Equations. Values of the activation energy and the pre-exponential factor of the dehydration were calculated. The results of thermal experiments and kinetic parameters indicated that borogypsum is similar to gypsum from dehydration mechanism point of view although it consists of boron and small amount of alkali metal oxides.
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