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In this paper we present moisture, temperature, and dehydration profiles of gypsum. Gypsum was chosen as a benchmark material for different reasons. First, all of the above mentioned mechanisms such as boiling, and dehydration take place in gypsum. The dehydration reaction(s) take place at well defined and relatively low temperatures.
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When hardened gypsum is exposed to the elevated temperature, the dehydration starts at the temperature about 60 °C . The dehydration is usually two-step process; firstly, the calcium sulphate hemihydrate is formed and later anhydrite, usually at temperatures below 200 °C. Both steps take place in a relatively wide temperature range …
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The dehydration products of gypsum under different temperature and water vapor pressure were investigated by thermodynamic theory. Additionally, the rehydration mechanism of soluble anhydrite was ...
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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 ...
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The autoclave method operated gypsum dehydration under elevated temperature and pressure [19], resulting in high running cost. Nevertheless, the hydrothermal technique meant the preparation of α-HH from FGD gypsum by salt solution method under atmospheric pressure, and inorganic acids or their salts were used as the dehydration …
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Unlike gypsum plaster without filler, the heat flow is reduced even after gypsum dehydration and the temperature of the unexposed side after the isothermal stage is stabilized.
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temperature. The dehydration temperature depends on the measurement method, the gypsum origin (natural, FGD), the type of required calcium sulfate hemihydrate (β), and the conditions during the α, experiment (pH, humidity, etc.), and this temperature signicantly diers in the literature. For instance, val-ues in Table 2 can be found.
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Figure 1: (left) Mass vs. temperature curves of gypsum during heating as measured by TGA. Two experiments were performed: open and closed. ... The temperatures measured on this front are comparable to the temperatures related to the second dehydration of gypsum. This second front can therefore be identi fied as the second dehydration reaction.
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concrete and mortar. In order to regulate the cement binding duration, natural gypsum may be replaced with anhydrite [5, 6]. Synthetic anhydrite is obtained when gypsum is dehydrated at the temperature of 600 to 800ºC [7]. There is little knowledge about the influence of the dehydration temperature on
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The dehydration products of gypsum under different temperature and water vapor pressure were investigated by thermodynamic theory. Additionally, the rehydration mechanism of soluble anhydrite was also studied by Monte Carlo (MC) simulations. The …
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Influence of the Gypsum Dehydration Temperature and Alkali ...
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The thermodynamic calculation results reveal that the dehydration mechanism of gypsum significantly depended on ambient temperature and water vapor pressure. In the high …
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The first describes the process of water leaving the structure of gypsum to form hemihydrate or anhydrite. The second depicts the temperature-dependent solubility of the …
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The temperature and humidity dependent formation of different crystalline phases CaSO 4 ·xH 2 O with 0 ≤ x ≤ 2 was investigated by in situ X-ray powder diffraction using a Bruker D8 diffractometer equipped with an Anton Paar CHC + cryo−/ humidity chamber. By isothermal measurements over time ranges up to 60 h at temperatures between 76 °C and …
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The dependence of the solubility of gypsum on temperature is nonlinear, reaching a maximum at 43°C. ... the dehydration of gypsum due to the effects. of high pressure and temperature during ...
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The dependence of the solubility of gypsum on temperature is nonlinear, reaching a maximum at 43°C. ... the dehydration of gypsum due to the effects. of high pressure and temperature during ...
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Find the latest published documents for gypsum dehydration, Related hot topics, top authors, the most cited documents, and related journals
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The temperature at which the gypsum binder (calcium sulfate hemihydrate) is industrially produced, between 80 and 180 °C, is often mentioned in the literature …
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Hydrothermal AFM has been used to study the thermal dehydration reaction on gypsum (010) surfaces in solutions at different saturation states, and in the absence of a bulk liquid phase. ... surface energy related to kink sites or individual point defects seems to be insufficient to trigger dehydration. The temperature-dependent lateral pit ...
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Gypsum caprocks' sealing ability is affected by temperature–pressure coupling. Due to the limitations of experimental conditions, there is still a lack of triaxial stress–strain experiments that simultaneously consider changes in temperature and pressure conditions, which limits the accuracy of the comprehensive evaluation of the brittle plastic evolution and …
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The dehydration path gypsum–bassanite–anhydrite III was shown to have strong parallels to a physical drying process, which depends on many parameters beyond the burning temperature.
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This study examined the thermal dehydration characteristics of CaSO 4 ∙2H 2 O in a constant-volume rotary vessel. The experiment used CaSO 4 ∙2H 2 O particles obtained from the crushed waste gypsum board. The particle size ranged from 850 to 2000 μm, and the experiment was carried out at varying rotation speeds of 1, 10, and 35 rpm, with the vessel temperature …
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Cooling is necessary to limit the temperature rise of the cement. This is done by a mixture of both air-cooling and water-cooling, including spraying water inside the mill. ... Cement milling and gypsum dehydration. Because the cement gets hot due to the heat generated by grinding, gypsum can be partly dehydrated, forming hemihydrate, or ...
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The test results of water absorption during high-temperature dehydration gypsum rock immersion and hydration are shown in Figure 9a. It can be seen that the hydration water absorption rate increased rapidly within 0–20 min, and the water absorption amount and the water absorption time were in a logarithmic relationship; after 20 min, the ...
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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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The commercial rock gypsum studied generates both hemihydrate and anhydrite at 128°C, and its impurities do not dehydrate until the temperature is increased to 500°C.
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Conclusion The work undertaken has demonstrated how the Portland clinker-gypsum grinding temperature can influence the early hydration behaviour of Portland cement. This can be associated with a direct effect upon the …
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The unit- 806 LOW-TEMPERATURE DEHYDRATION OF GYPSUM SINGLE CRYSTALS 807 (a) (a) (b) Li a O2 O1 O1 O2 O2 OW O2 b O2 X O2 Z S Y H2 H1 O1 c (b) Li Fig. 2. (a) Projection of the gypsum structure on the (001) plane. The periodicity b is determined by two double layers, between which water molecules are concentrated. ...
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low-temperature dehydration of gypsum has been inves-tigated for many years. The rst analysis of the process is attributed to Flörke (1952), which indicated a two-step process CaSO 4 ·2H 2 O CaSO 4 ·0.5H 2 O -CaSO 4.An early study of the kinetics of dehydration of gypsum was performed, in vacuo, by Molony & Ridge (1968) whose
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Abstract. 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 MPa by using a hydrothermal diamond anvil cell and Raman spectroscopy. Kinetic analysis shows that the dehydration rate k increases with pressure, suggesting a negative pressure …
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