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chemical equation dehydration of gypsum

chemical equation dehydration of gypsum
Dehydration Pathways of Gypsum and the Rehydration

Some researchers have argued that gypsum undergoes a two-stage dehydration process, where β-CaSO 4 0.5H 2 O is formed first and then γ-CaSO 4 is obtained by further dehydration of β-CaSO 4 0.5H 2 O. McAdie studied the gypsum dehydration process at

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From atom level to macroscopic scale: Structural mechanism of gypsum ...

2022年4月1日  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

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Dehydration Pathways of Gypsum and the Rehydration Mechanism

2019年4月26日  In the high-temperature and low water vapor pressure region, gypsum dehydrates to form γ-CaSO 4 in a single-step process (CaSO 4 2H 2 O → γ-CaSO 4 );

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The Dehydration Kinetics of Gypsum in a Fluidized Bed Reactor

2000年10月1日  Common equations arebased on diffusion, phase boundary and nucleation steps being rate determining.At least ten different models and mechanisms have

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Kinetics of Gypsum Dehydration - Springer

2017年8月25日  According to the thermal curves, the gypsum dehydration comports two steps described by the following equations: CaSO 4 •2H 2 O( s )→CaSO 4 •1/2H 2 O( s

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Structural evolution of gypsum (CaSO42H2O) during thermal dehydration ...

2022年12月6日  Therefore, β-hemihydrate dehydration can be translated by the chemical formula CaSO4xH2O (0.5 ≤ x ≤ 0.8).

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Novel approach to thermal degradation kinetics of

2020年3月26日  It has been shown that the thermal dehydration of gypsum undergoes a two-step process at high PH2O, with the formation of an intermediate hemihydrate

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Structural evolution of gypsum (CaSO42H2O) during

Gypsum crystallizes in monoclinic space groups I2/a (Pedersen and Semmingsen, 1982) and C2/c (Boeyens and Ichhar- am, 2002), which are essentially the same space group

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Fast in-situ X-ray scattering reveals stress sensitivity of gypsum ...

2021年5月24日  The dehydration of gypsum to hemihydrate has been studied for decades because it is an important model reaction for understanding fluid-triggered earthquakes,

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Gypsum plasterboards under natural fire - Ex-perimental

2021年7月15日  gypsum plasterboards (like Type F or Type X) are examined using vari-ous testing methods and procedures. According to chemical formula-tion of gypsum plasterboards, the thermal properties vary.11 This results in different courses of the thermal properties, which leads to a limited comparability. In Figure 1, the functions for the

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Dehydration Pathways of Gypsum and the Rehydration

2019年4月4日  Over the past decades, many studies have proposed the existence of various subhydrates with a general chemical formula of CaSO 4 nH 2 O, where the numerical value of n ranges from 0 to 0.67. 25,28 If the dehydration product CaSO 4 nH 2 O occurs upon the heating of gypsum, then the dehydration reaction of gypsum can be

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(PDF) Dissolution and conversions of gypsum and

2000年4月1日  Gypsum dissolves by a simple two-phase dissociation. Anhydrite, when dissolved, forms a solution of calcium sulfate, which at common temperatures and pressures is in equilibrium with the solid ...

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Gypsum: a review of its role in the deterioration of ... - Springer

2006年12月2日  The deterioration of buildings and monuments by gypsum is the result of crystallization cycles of this salt. Although gypsum can dehydrate to a hemihydrate, the mineral bassanite, and to an anhydrate, the mineral anhydrite, this reaction occurs in nature on a geological time scale and therefore it is unlikely to occur when gypsum is found on

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Preparation of Plaster of Paris Class 10 - REMEDIAL CLASSES

2023年7月30日  Preparation method of Plaster of Paris. Plaster of Paris is prepared by heating gypsums at 373K, partial dehydration takes place and Plaster of Paris is obtained. Following is the Chemical equation for the preparation of plaster of Paris. 2C aSO4. 2H 2O 373K −→ 2C aSO4. ½H 2O + 3H 2O 2 C a S O 4. 2 H 2 O → 373 K 2 C a S O 4. ½ H 2

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Gypsum board reaction kinetics at elevated temperatures

2012年2月10日  Highlights. We study the gypsum board chemical reactivity at elevated temperatures. We perform DSC measurements at different heating rates. We define the ‘kinetic triplet’ of each of the reactions involved. Gypsum dehydration reaction found to be a three step reaction. Gypsum crystal structure reorganization reaction is a one step reaction.

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A 4D view on the evolution of metamorphic dehydration reactions

2017年7月31日  Gypsum dehydration has proven to be analogous to reactions involving silicate minerals 18 but is much more suitable for synchrotron study since it completes in hours rather than years and begins ...

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Temperature and humidity dependent formation of CaSO

2020年4月1日  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

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Calcium Sulfate Dihydrate - an overview ScienceDirect Topics

Gypsum is the name given to a mineral categorized as calcium sulfate mineral, and its chemical formula is calcium sulfate dihydrate, CaSO 4 ⋅ 2H 2 O. However, a broader definition includes all the calcium sulfates, including calcium sulfate hemihydrate, CaSO 4 ⋅ 0.5H 2 O, which is known as plaster or plaster of Paris (POP).

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Mechanism and kinetics of gypsum–anhydrite

2011年6月1日  In the present work, gypsum–anhydrite transformation in pure water was studied at 90 °C, 150 °C and 200 °C.The results showed that the transformation kinetics was significantly slower at 90 °C, such that in the absence of anhydrite seeds gypsum remained stable and no transformation was observed.Addition of 10 wt.% of anhydrite seeds

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Mechanism and kinetics of gypsum–anhydrite

2011年6月1日  In the present work, gypsum–anhydrite transformation in pure water was studied at 90 °C, 150 °C and 200 °C.The results showed that the transformation kinetics was significantly slower at 90 °C, such that in the absence of anhydrite seeds gypsum remained stable and no transformation was observed.Addition of 10 wt.% of anhydrite seeds

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Study of gypsum by PDSC Journal of Thermal Analysis and Calorimetry

2012年3月18日  The chemical formula is CaSO 4 2H 2 O (calcium sulfate dihydrate) [ 3 ]. Thermal analysis techniques, such as combined differential scanning calorimetry (DSC)/thermogravimetry (TG), are very suitable to characterize dehydration processes of gypsum [ 4, 5] and other mineral compounds [ 6 ]. On heating, gypsum undergoes two

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Thermal behaviour and kinetics of dehydration of gypsum in

2009年1月11日  Thermal behaviour and kinetics of dehydration of gypsum in air have been investigated using in situ real-time laboratory parallel-beam X-ray powder diffraction data evaluated by the Rietveld method. Thermal expansion has been analysed from 298 to 373 K. The high-temperature limits for the cell edges and for the cell volume, calculated using

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Thermo-poro-mechanics Modelling of Gypsum Dehydration

2017年7月12日  The governing equations are integrated numerically using the finite element method. The obtained results show a significant correlation between gypsum dehydration and creation of fluid pathways. The proposed model can be generalised to describe the effects of dehydration in other minerals carrying water in their crystal

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Thermal analysis application: Gypsum - Linseis Messgeräte

4 天之前  The double-step dehydration of calcium sulphate-dihydrate appears between 100°C and 300°C. The first step is the forming of half-hydrate (CaSO4 ∙ 2H2O to ... The chemical formula of Gypsum is CaSO4 ∙ 2H2O (Calcium Sulfate Dihydrate). There are a large number of uses for gypsum as a building material. Gypsum is a dry powder that is

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Dehydration Pathways of Gypsum and the Rehydration

2019年4月26日  Over the past decades, many studies have proposed the existence of various subhydrates with a general chemical formula of CaSO 4 nH 2 O, where the numerical value of n ranges from 0 to 0.67. 25,28 If the dehydration product CaSO 4 nH 2 O occurs upon the heating of gypsum, then the dehydration reaction of gypsum can be

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Experimental Study on Physical and Mechanical Properties of Gypsum

2021年1月5日  In order to study the physical and mechanical properties of gypsum rock samples in three states (natural, high-temperature dehydration and hydration time), natural gypsum rock was put into high-temperature condition of 220°C for dehydration treatment, and then the high-temperature dehydrated gypsum rock was treated with different

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Thermal Analysis of Calcium Sulfate Dihydrate Sources Used

2016年7月1日  The chemical formula of gypsum is CaSO 4 Á2H 2 O and in its thermal analysis turns into CaSO 4 Á2H 2 O by losing some of the water at 133°C and finally turns into anhydrite (CaSO 4 ) by losing ...

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Gypsum Board Reaction Kinetics at Elevated Temperatures

2012年2月1日  The chemical kinetics of three main reactions that take place when a gypsum board is exposed at elevated temperatures: evaporation of free moisture content, dehydration of chemically bound water ...

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