cheCimentl equation dehydration of gypsum

Dehydration Pathways of Gypsum and the Rehydration

Their experimental results reveal that gypsum dehydration proceeds through only a single CaSO 4 2H 2 O → γ-CaSO 4 step when the ambient water vapor pressure is less than 26664 Pa; however, a two-step process of CaSO 4 2H 2 O → β-CaSO 4 0.5H 2 O → γ

Dehydration‐induced damage and deformation

2012.3.10 [56] We performed drained dehydration tests on Volterra gypsum in hydrostatic and creep conditions, while monitoring AEs and

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

2022.4.1 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

The dehydration process of gypsum under high pressure

2017.8.29 gypsum-anhydrite dehydration reaction sequences at simultaneous high-pressure and temperature conditions. Mirwald (2008) performed a study of CaSO 4 H 2O

The dehydration process of gypsum under high pressure

2011.9.30 Mirwald ( 2008) performed a study of CaSO 4 H 2 O system by differential pressure analysis (DPA), following the dehydration process up to 623 K and 3.5 GPa and

Dehydration of gypsum waste to recyclable anhydrite using

2023.10.3 Here, we report the first solid-like dehydration of gypsum to produce anhydrite at room temperature. Specifically, a 39 nm thick sulfuric acid film (NSF) was

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

2021.5.24 Our results open research avenues on the fundamental thermo-mechanics of crystal hydrates and the interaction of stress and chemical reactions in crystalline

Dehydration Pathways of Gypsum and the Rehydration Mechanism

2019.4.26 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);

Thermal behaviour and kinetics of dehydration of gypsum in

2009.1.11 Dehydration of gypsum has been investigated in isothermal conditions within the 348–403 K range with a temperature increase of 5 K. Dehydration proceeds

Thermal behaviour and kinetics of dehydration of gypsum in

2009.1.11 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

Structural evolution during the dehydration of

2009.6.1 (a) Surface plot of angle-dispersive diffraction patterns (collected at station 6.2, SRS, UK, using a wavelength of 1.4000(2) A ˚ ) obtained during the dehydration of a pure gypsum system within ...

Transition of anhydrite into gypsum - HYDRATION CAVES

The key temperature during the transformation of anhydrite into gypsum is 42 ° C, which is characteristic for a depth of approx. 900-1200 m (Mossop and Shearman 1973). However, this depth is not a factor in maintaining such a temperature, and the occurrence of anhydrite on the earth’s surface, despite the temperature drop, still occurs ...

Dehydration‐induced damage and deformation in gypsum

2012.3.10 Volterra gypsum in an evaporitic rock, and groups (up to centimeter scale) of neighboring grains with similar crystal orientations are commonly found (see Fusseis et al. for a detailed investigation of the fabric of Volterra gypsum). The onset of dehydration can thus be marked by the development of heterogeneities in elastic properties.

The thermal dehydration of natural gypsum and pure calcium sulphate ...

1996.7.10 The mean weight loss for natural gypsum was 7.39 0.91 % of the original reactant weight. On calculation it would appear that only - 35% of the sample is calcium sulphate dihydrate. The DSC curve for the dehydration of calcium sulphate dihydrate shows a double peak which was not present in the DSC curve for the dehydration of natural

Dehydration of gypsum waste to recyclable anhydrite using

2023.10.3 Here, we report the first solid-like dehydration of gypsum to produce anhydrite at room temperature. Specifically, a 39 nm thick sulfuric acid film (NSF) was fabricated to extract water of crystallization from gypsum and simultaneously enable a phase transformation from gypsum to anhydrite via recrystallization. Using density functional

Experimental Study on Physical and Mechanical

2021.3.12 of rehydration of gypsum rock after high-tempera-ture dehydration is an urgent topic, which is very important for the stability and airtightness of salt cavity storage. Scholars at home and abroad have done a lot of research on the physical and mechanical properties of gypsum rock and salt rock, and achieved more valuable results.

In situ IR spectroscopic and thermogravimetric study of

2009.11.4 Thedehydration of gypsum CaSO4.2H20 has been studied, at negligible water vapour pressure, by in situ infrared (IR) spectroscopy and by thermogravimetry to determine whether intermediate phases (CaSO4.nH20) exist, other than the hemihydrate with n=0.5, andalso tcompare th mecha-nism ofthe dehydration process when measured

Dehydration Pathways of Gypsum and the Rehydration

2019.4.4 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

Gypsum dehydration potential and mean residence time of a

The gypsum dehydration capability determined under the given test conditions of about 26% in the vertical stirred media mill can be considered as relatively low compared with the dehydration capability of ball mills (up to 100%). Comparable grinding trials in a semi-industrial horizontal SMM have shown that with fairly long operating times ...

An in situ real-time monitoring of the hydration and dehydration

2023.10.12 The molecular structure and the identified vibrational characteristic Raman bands can be used to monitor compounds' compositional and phase transformation [16].A series of Raman spectra of the gypsum powder (dihydrate CaSO 4 2H 2 O) and gypsum paste prepared are captured to monitor the hydration and dehydration process

(PDF) Dissolution and conversions of gypsum

2000.4.1 carbonate rocks. 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 ...

Dehydration reactions of gypsum: A neutron and X-ray

1990.3.1 The powder was prepared on a 0.02-mm-thick Al-sputtered Mylar foil. The dehydration reaction at a constant temperature of 335 (1) K was recorded with 10 dif-fractograms in time intervals of 12 min (6 range 5-25. Starting at ambient temperature, the 335 K level was reached in about 5 min. Results Figure 1 shows the three-dimensional

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

2022.4.1 Introduction. 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 O) or γ-anhydrite

An in situ real-time monitoring of the hydration and dehydration

2023.10.12 Section snippets Materials and methods. The gypsum specimens used in the study are laboratory-grade gypsum, with a density of 2.320 g/cm 3 and molecular weight of 172.17 g/mol (Sigma-Aldrich, U.S.A.), and are used as received without processing or the addition of chemical additives to modify the setting time and other properties of the paste.

Kinetics of Gypsum Dehydration at Reduced Rressure: An

2008.8.1 The exponential factor m in the Avrami-Erofeev equation obtained for crystals ranges between 1.02 and 1.31, suggesting that, unlike powders, the dehydration process in crystals is not a purely ...

Dehydration behavior of FGD gypsum by simultaneous TG

2010.10.26 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

The dehydration process of gypsum under high pressure

2011.9.30 The effects of pressure on the dehydration of gypsum materials were investigated up to 633 K and 25 GPa by using Raman spectroscopy and synchrotron X-ray diffraction with an externally heated diamond anvil cell. At 2.5 GPa, gypsum starts to dehydrate around 428 K, by forming bassanite, CaSO4 hemihydrate, which completely

Insights Into the Micromechanics of Dehydration‐Induced Gypsum

2024.1.3 Here, we examine the micromechanical status of syn- and post-dehydration gypsum-phases, crucial for understanding intra-crystalline deformation. We micro-indented the (010) planes of natural gypsum crystals from 30 to 140°C at various strain-rates to track mechanical changes during progressive dehydration and phase transition.

Thermal conductivity of gypsum boards beyond dehydration

The present study investigates the significant rise in thermal conductivity of dehydrated gypsum plaster board between 200 and 800 °C, reaching the initial hydrated value of 0.3 W/(mK). It is shown that the main reason for this increase is independent of radiative and convective heat transfers and only due to an enhancement of the conduction ...

The thermal dehydration of synthetic gypsum - ScienceDirect

1995.12.20 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 via a process with an activation energy of 392 ± 100 kJ mol −1 for α-values between 0 and 0.1. For α-values between 0.1 and 0.7, the reaction can be described by a first-order ...

(PDF) The thermal dehydration of natural gypsum and pure

The mean weight loss for natural gypsum was 7.39 k 0.91% of the original reactant weight. On calculation it would appear that only - 35% of the sample is calcium sulphate dihydrate. The DSC curve for the dehydration of calcium sulphate dihydrate shows a double peak which was not present in the DSC curve for the dehydration of natural gypsum.

Dehydration Pathways of Gypsum and the Rehydration

2023.10.27 Their experimental results reveal that gypsum dehydration proceeds through only a single CaSO4. 2H2O. is less → γ-CaSO4 step when the ambient water vapor pressure than 26664 Pa; however, a ...

Gypsum Properties, Formation, Uses and Deposits

2023.9.9 Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate (CaSO42H2O). It is commonly found in sedimentary rock formations and is often associated with other minerals such as anhydrite, halite, and sulfur. The name “gypsum” is derived from the Greek word “gypsos,” which means “plaster” or “chalk.”.

Ingenious approach for retrieving valuable metals from gypsum

2024.7.1 As a common waste obtained from various industries, gypsum contains various VMs (Cr, Cd, Pb, Hg, As, Be, Tl, etc.); annually, 20 million tons of gypsum are discharged in China [6].It is an abundant low-grade mineral on earth (reserve of > 2 billion tons), which is confirmed to contain 0.05–1 wt% U, Ce, Sr, etc [7].Therefore, gypsum is

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

2021.5.24 The dehydration of gypsum to hemihydrate has been studied for decades because it is an important model reaction for understanding fluid-triggered earthquakes, and due to the global use of plaster ...

The dehydration kinetics of gypsum at high pressure and

2015.4.29 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

Thermal properties and microstructure of gypsum board and

2011.9.21 Dehydration reaction of gypsum boards was investigated from both micro and macro levels, employing thermogravimetric analysis and a ventilated oven. A new dehydration mechanism of gypsum was proposed. The thermal properties of gypsum board such as enthalpy of reaction, specific heat capacity, and thermal conductivity were

Kinetics of Gypsum Dehydration - Springer

2017.8.25 Abstract. The kinetics of gypsum dehydration in non-isothermal conditions with constant heating rate as well. in quasi-isotherm, quasi-isobar regime, was investigated. The latter ones of these methods allowed. putting in evidence the autocatalytic character of the dehydration, as well as the change of the activa-. tion energy with the conversion.

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cheCimentl equation dehydration of gypsum

Dehydration Pathways of Gypsum and the Rehydration

Dehydration‐induced damage and deformation

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

The dehydration process of gypsum under high pressure

The dehydration process of gypsum under high pressure

Dehydration of gypsum waste to recyclable anhydrite using

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

Dehydration Pathways of Gypsum and the Rehydration Mechanism

Thermal behaviour and kinetics of dehydration of gypsum in

Thermal behaviour and kinetics of dehydration of gypsum in

Structural evolution during the dehydration of

Transition of anhydrite into gypsum - HYDRATION CAVES

Dehydration‐induced damage and deformation in gypsum

The thermal dehydration of natural gypsum and pure calcium sulphate ...

Dehydration of gypsum waste to recyclable anhydrite using

Experimental Study on Physical and Mechanical

In situ IR spectroscopic and thermogravimetric study of

Dehydration Pathways of Gypsum and the Rehydration

Gypsum dehydration potential and mean residence time of a

An in situ real-time monitoring of the hydration and dehydration

(PDF) Dissolution and conversions of gypsum

Dehydration reactions of gypsum: A neutron and X-ray

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

An in situ real-time monitoring of the hydration and dehydration

Kinetics of Gypsum Dehydration at Reduced Rressure: An

Dehydration behavior of FGD gypsum by simultaneous TG

The dehydration process of gypsum under high pressure

Insights Into the Micromechanics of Dehydration‐Induced Gypsum

Thermal conductivity of gypsum boards beyond dehydration

The thermal dehydration of synthetic gypsum - ScienceDirect

(PDF) The thermal dehydration of natural gypsum and pure

Dehydration Pathways of Gypsum and the Rehydration

Gypsum Properties, Formation, Uses and Deposits

Ingenious approach for retrieving valuable metals from gypsum

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

The dehydration kinetics of gypsum at high pressure and

Thermal properties and microstructure of gypsum board and

Kinetics of Gypsum Dehydration - Springer

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