— The main dehydration of the calcium sulphate dehydrate part of synthetic gypsum occurs between 95 and 170°C (heating rate 5°C min −1) and seems to proceed …
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temperature dehydrated gypsum rock was treated with different hydration time, and the gypsum rock samples in three states were subjected to ultrasonic test, density test and uniaxial compression test. The results show that the main components of natural gypsum minerals were gypsum dihydrate (71%), dolomite (27%) and potassium chloride (2%). …
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— In cases that the core of a gypsum board might contain magnesium and calcium carbonate, a reduction of gypsum mass is observed, at the temperature range between 600 and 800 °C, which corresponds to the decomposition of magnesium carbonate [9], [22], [23] and calcium carbonate [3], [9], [24], [25]: (2.6) MgCO 3 (s) ↔ MgO (s) + …
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— Methods. The dehydration process of FGD gypsum was performed with simultaneous TG/DSC analysis (NETZSCH STA 409 Luxx, Selb/Bavaria, Germany) at N 2 atmosphere with a gas flow of 20 mL min −1.Non-isothermal analysis was carried out at different heating rate (2−20 K min −1).Isothermal analysis was conducted in the …
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The thermal behavior of gypsum boards was investigated by means of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and thermal conductivity …
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Calcium sulfate dihydrate (gypsum) is a commonly found mineral in the nature, and it is an important building ... produced only when the decomposition occurred at high P H 2O and below 115 C, while the anhydrite was formed above 115 C and at low P H ... focused on the FGD gypsum dehydration behavior until now [26]. The origin, i.e., different ...
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— Gypsum of chemical formula CaSO 4 ·2H 2 O, also called calcium sulfate dihydrate, is a versatile material used in several sectors of activity such as cement industry, plaster manufacturing and agriculture [1, 2].It is also found in the formulation of many useful products like paper, glass and paints [3, 4].Gypsum production is carried out in two …
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4-1 Temperature Change in Drying and Dehydration of Gypsum in a Fluidized Bed Fig. 2 illustrates a typical change of interior tempera-tures with time during the drying and …
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— The specimens tested exhibited the thermal and gravimetric profiles typical of calcium sulfate dihydrate decomposition into the temperature range of ambient to 250 …
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— The performance of composite gypsum at elevated temperatures depends on the treatment temperature and reflects the combined effects of gypsum phase change and the filler effects of silica flour or talc powder. ... There was tremendous pore water loss, and gypsum dehydration happened at 100 °C and 200 °C, leading to a porous structure that ...
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Figure 1 shows the TG/DTA results for dihydrate gypsum. A 30mg sample was placed in a semi-hermetically sealed container, which was a hermetically sealed aluminum container with a pinhole in the lid. The atmosphere was 200ml/min of air …
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— Abstract The dehydration of gypsum CaSO4.2H2O has been studied, at negligible water vapour pressure, by in situ infrared (IR) spectroscopy and by thermogravimetry to determine whether intermediate phases (CaSO4.nH2O) exist, other than the hemihydrate with n=0.5, and also to compare the mechanism of the dehydration …
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This article investigates the thermal performance of gypsum boards in the dehydration temperature region, where pronounced chemical reactivity is anticipated. Gypsum board samples were gradually heated up to 300°C, using a low heating rate.
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— Mass losses vary between 13.7 and 16.5% and heat of dehydration values between 377 and 420 J g−1 for the dehydration of ground and mixed inhomogeneous gypsum samples. As for the dehydration of ...
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The formation of beta-hemihydrate is an endothermic reaction as well. During the phase decomposition of dihydrate to hemihydrate, the temperature inside of the crystal should not increase above the decomposition temperature in …
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— At higher temperatures the super-saturation is lower and the expected reaction speed is lower. However, as the ions can move faster at higher temperature, the speed of the hydration reaction is increased. With a higher temperature fewer seeds are formed and the gypsum crystals can grow larger (Figure 3d - f).
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— Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate (CaSO4·2H2O). ... 190°C (300°F to 375°F), it loses some or all of its water content. This process is called calcination. The degree of …
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THE differential thermograms of calcium sulphate dihydrates (gypsums) show two relatively large endothermic effects in close sequence below 250° C. There is general agreement1,2 that these two effects represent the two-step decomposition of the dihydrate to hemihydrate and to soluble anhydrite. A third small endothermic effect, which is always associated …
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— The structure and composition of the gypsum at elevated temperatures were studied by means of scanning electron microscopy, X-ray diffraction (XRD) and thermogravimetry (TG). The gypsum paste samples were heated to the temperatures from 50 to 1000 °C. The changes in the structure of gypsum were in good accordance with …
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— Semantic Scholar extracted view of "The thermal dehydration of synthetic gypsum" by C. Strydom et al. ... An in situ dehydration kinetics study of gypsum under water-saturated condition was performed in the temperature and pressure ranges of 383–423 K and 343–1085 ... calcium sulphate dihydrate undergoes dehydration as …
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— In general, it seems not necessary to decompose the 0.3-hydrate, which is only possible at temperatures of about 180 °C, since the decomposition at lower pressure takes place with monohydrate as intermediate phase which decomposes at much lower temperatures. This is beneficial for a thermochemical storage since the decomposition …
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— 1. Introduction1.1. General context. Gypsum plaster is an inorganic binder that is prepared in a two-step process. The first step is dehydration: heated to 100–200 °C, gypsum (CaSO 4 ·2H 2 O) releases water as vapor [1, 2] and, depending on temperature and water vapor partial pressure (p H2O) [3, 4] forms either hemihydrate (CaSO 4 •½H 2 …
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— The plot of the solubility product values against pressure and temperature according to Eqs. 2 to 4, for both gypsum and anhydrite, is shown in Fig. 5.
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— We studied the kinetics and mechanism of the dehydration reaction of calcium sulfate dihydrate to hemihydrate under controlled temperature and water vapor partial pressure.
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— Introduction. Gypsum products are created from two simple reactions [1]: the calcination reaction − CaSO 4 ·2H 2 O + heat → CaSO 4 ·½H 2 O + 3/2H 2 O (g), and the rehydration reaction − CaSO 4 ·½H 2 O + excess water → CaSO 4 ·2H 2 O + excess water (g). An ore of calcium sulfate dihydrate should exhibit four distinct thermal …
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— This article addresses the thermal properties and the microstructure of gypsum boards produced from β-hemihydrate by studying its dehydration process. …
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— The thermal decomposition of zinc acetate dihydrate was studied by TG–DSC to better understand its thermal stability and decomposition temperature. Fig. 4 (a) shows typical TGA and DSC curves of zinc acetate dihydrate in an air flow of 100 sccm at a heating rate of 2 °C min −1. The process starts with an endothermic reaction …
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— The calcium sulphate dihydrate gypsum (CaSO 4 ·2H 2 O) is the most common sulphate evaporite mineral on our planet 1.Sulphate evaporites play an important role in Earth's sulphur cycle and are ...
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— We studied the kinetics and mechanism of the dehydration reaction of calcium sulfate dihydrate to hemihydrate under controlled temperature and water vapor partial pressure. From kinetic and reaction …
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— In this work, the dehydration pathways of gypsum and the rehydration mechanism of soluble anhydrite were mainly investigated by thermodynamic modeling and MC simulations. The dehydration pathways of gypsum are largely determined by …
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— Dehydration experiments revealed that the most important variables that control the rate of the gypsum-to-bassanite transformation are temperature and water vapour pressure (Ball & 2 Norwood, 1969 ...
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— In 1903, Jacobus Henricus van't Hoff and his co-workers gave a transition temperature for the gypsum–hemihydrate reaction of 107 °C and proposed the existence of a soluble anhydrite form in the wrong assumption of a direct dehydration of gypsum without the intermediate hemihydrate step at 93 °C, which was confirmed and revised ...
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This subhydrate material is mixed with water at a construction site to form dihydrate (gypsum) again. Therefore, the dehydration process of gypsum and the rehydration of hemihydrate were investigated in several studies; the given references will give an overview of the research conducted up to now [3–15].
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— Engbrecht & Hirschfeld (2016) carried out an investigative research on the thermal behavior of calcium sulfate dihydrate and in their studies it was proven that the gypsum sample investigated ...
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