how to dehydrate gypsum into hemihydrate gypsum in Oman

Influence of fluoride ion on the performance of PCE in hemihydrate

Starting from the mixing of hemihydrate gypsum and water, the moment when the steel needle cannot reach the bottom of the mold was considered as the initial setting time. When the steel needle was inserted into the hemihydrate gypsum slurry to a depth less than 1 mm, the time consumed in this period was recorded as the final setting …

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Investigation of hydration mechanisms of alpha and beta hemihydrate …

1 Introduction . Calcium sulfate hemihydrate [CaCO 4 ∙ 0.5H 2 O(s)] can be found naturally in very dry climate regions in Egypt, Australia, Death valley and Kuwait as bassanite, but in the presence of water or humid atmosphere it can convert to dehydrate [1, 2]. Therefore, the production of hemihydrate industrially has been studied widely through the …

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The dehydration process of gypsum under high …

2.5 GPa, gypsum starts to dehydrate around 428 K, by forming bassanite, CaSO 4 hemihydrate, which completely dehydrates to c-anhydrite at 488 K. All the sulphate modes decrease linearly between 293 and 427 K with temperature coefﬁcients ranging from -0.119 to -0.021 cm-1 K-1, where an abrupt change in the m 3 mode and in the

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Gypsum | Properties, Formation, Uses and Deposits

Gypsum is a naturally occurring mineral that has been used by humans for various purposes for thousands of years. It is a versatile mineral with a wide range of applications in construction, agriculture, industry, and even art. In this introduction, we'll explore the definition and composition of gypsum.

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The setting of gypsum plaster

QXRD results show the transformation of gypsum into hemihydrate after a residence time of 8 h and 4 h. SEM images distinguish the α‐HH and β‐HH modifications. For fgd‐gypsum pellets, the ...

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Understanding gypsum in 3 diagrams

The dehydration of gypsum can be observed using thermo-gravimetric measurement and differential scanning calorimetry. Depending on the parameters of …

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Effect of tricalcium aluminate and nano silica on …

In this article, tricalcium aluminate (C 3 A) was utilized as addition agent for hemihydrate gypsum (HHG) to improve the performance of gypsum pastes, and on that basis, the optimal dosage group of C 3 A was selected for further study on the composite effect with nano-silica (NS). HHG plasters with 0–5% content of C 3 A and besides …

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Formation of α-Hemihydrate Inside of a Gypsum …

Gypsum crystal partly dehydrated, cleaved along cleavage plane, with observable dihydrate, α-hemihydrate and β-hemihydrate. Yellow circle = still dihydrate, blue circle = alpha hemihydrate, red circle …

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Insights Into the Micromechanics of Dehydration‐Induced Gypsum …

The Gypsum-Hemihydrate phase exhibits strain-rate sensitive elastoplastic deformation between 30 and 110°C, as hardness decreases with increasing strain-rate. We propose that delamination of the layers and extensive tensile cracking along [010] cause this strain-rate sensitive behavior, displaying Indentation Size Effect.

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Fast in-situ X-ray scattering reveals stress sensitivity of …

Upon heating, gypsum gradually loses its water, transforming into the hemihydrate, also known as bassanite, (CaSO 4 ·0.5H 2 0) and anhydrite (CaSO 4). …

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Experimental research on desulfurization gypsum with …

Adding gypsum to the starting mixtures, hemihydrate dehydrated form of the gypsum reacted with lime and quartz to form hexagonal prisms of hydroxyl ellestadite which grew radially, and inhibited ...

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Influence of calcination and GGBS addition in preparing β-hemihydrate …

This is because the main composition of PG is dihydrate gypsum (CaSO 4 ⋅2H 2 O), which can be dehydrated to form synthetic hemihydrate gypsum, like natural mineral gypsum. Depending on the temperature and condition of the dehydration process, natural gypsum exists in four different phases, namely hemihydrate gypsum (CaSO 4 …

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The dehydration process of gypsum under high pressure …

At 2.5 GPa, gypsum starts to dehydrate around 428 K, by forming bassanite, CaSO4 hemihydrate, which completely dehydrates to c-anhydrite at 488 K.

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Dissolution and conversions of gypsum and anhydrite

This way, James (1992) noted that in very hot climates gypsum can dehydrate to anhydrite when it is exposed at the surface, above 42 • C, or where high salinity is present. ...

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DM chapter 16: Gypsum & Wax Products Flashcards

Study with Quizlet and memorize flashcards containing terms like 1. Which of the following is true concerning the chemical properties of gypsum materials? a. Chemically, the mineral gypsum is a hemihydrate of calcium carbonate. b. To form the raw material into a powder, the manufacturer heats it and adds water. C. When the dihydrate is again mixed with …

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

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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New insights into the transformation of calcium sulfate hemihydrate …

New insights into the transformation of calcium sulfate hemihydrate to gypsum using time-resolved cryogenic transmission electron microscopy Langmuir. 2012 Jul 31;28(30) :11182-7. ... Their incorporation into a growing particle produces disorder and extends the time over which the amorphous phase exists. We see evidence of patches …

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Solved How much plaster of paris (gypsum hemihydrate) …

Our expert help has broken down your problem into an easy-to-learn solution you can count on. ... How much plaster of paris (gypsum hemihydrate) can be obtained by calcination of 1 ton of pure gypsum rock? (Ca: 40, O:16, S: 32, H:1) How much plaster of paris (gypsum hemihydrate) can be obtained by calcination of 1 ton of pure gypsum rock? (Ca ...

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Dehydration Pathways of Gypsum and the Rehydration …

The dehydration of gypsum (CaSO4·2H2O) into calcium sulfate hemihydrate (CaSO4·0.5H2O) and anhydrites (γ-CaSO4 and β-CaSO4) was carried out by heating under a const. pressure of water vapor using Controlled Transformation Rate …

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Calcium sulphate hemihydrate hydration leading to gypsum

Due to the slow hydration of anhydrate gypsum, additives, K2SO4 and hemihydrate gypsum were selected to … Expand. 12. Save. Hydroxyethyl methyl cellulose as a modifier of gypsum properties. P. Mróz M. Mucha. Materials Science. ... Hydration of calcium sulfate hemihydrate (CaSO4·H2O) into gypsum (CaSO4·2H2O). …

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Mechanism and kinetics of gypsum–anhydrite

The transformation of gypsum into anhydrite at low temperatures under atmospheric pressure as well as at elevated temperatures (150 °C and 200 °C) inside an autoclave was investigated by monitoring changes in both the liquid and solid phases.The effect of temperature, sulfuric acid addition, anhydrite seeding and addition of sulfate …

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The dihydrate‐hemihydrate transformation in gypsum

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 ...

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The Mechanochemical Process and H2SO4 Treatment on the …

Difference hydrothermal temperatures (80 and 130 °C) for 30 min were conducted to dehydrate the synthetic gypsum from fgd sludge to hemihydrate (CaSO 4 ⋅0.5H 2 O) to identify its potential to replace natural gypsum during the plaster of …

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Gypsum: a review of its role in the deterioration of …

At temperatures above the gypsum–hemihydrate transition, gypsum can be dehydrated to hemihydrate at any relative humidity (see Fig. 3) in a topotactic solid state reaction (Freyer and Voigt 2003). The …

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Microstructure and mechanical properties of β-hemihydrate …

Research highlights Water demand of β-hemihydrate was determined using spread flow test, and the influence of water content on the flowability was analyzed. The deformation coefficient of the β-hemihydrate was derived, the thickness of a water layer around the particles to assure the fluidity of the hydrating system was discussed, and …

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From atom level to macroscopic scale: Structural mechanism of gypsum

Plaster, made of calcium sulfate hemihydrate (CaSO 4 •½H 2 O) and/or γ-anhydrite (CaSO 4) is obtained by dehydration of gypsum (CaSO 4 ·2H 2 O) at 100–200 °C. When mixed with water, it dissolves while new gypsum crystals precipitate. Plaster's microstructures affect its reactivity and setting properties, but are poorly understood due …

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Promotion of conversion activity of flue gas …

Key words: flue gas desulfurization gypsum; α-hemihydrate gypsum; calcination-hydration treatment; dissolution; surface characteristics Cite this article as: GUAN Qing-jun, SUN Wei, GUAN Chang-ping, YU Wei-jian, ZHU Xiang-nan, Sultan Ahmed Khoso, WANG Ping, PENG Wen-qing. Promotion of conversion activity of FGD gypsum into α …

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Dehydration Pathways of Gypsum and the Rehydration …

gypsum is stable in the low-temperature and high water vapor pressure region and does not dehydrate to form any calcium sulfate hemihydrate. Finally, the rehydration mechanism of soluble

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The dihydrate‐hemihydrate transformation in gypsum

Plaster, made of calcium sulfate hemihydrate (CaSO4•½H2O) and/or γ-anhydrite (CaSO4) is obtained by dehydration of gypsum (CaSO4·2H2O) at 100–200 …

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Effect of Soluble Phosphorus on the Mechanical …

out transformation of PG into a-hemihydrate gyp-sum.18–21 However, the soluble phosphorus pre-sented in PG has a crucial inﬂuence on a-hemihydrate gypsum, and the inﬂuence degree of different forms of soluble phosphorus is unclear. Therefore, the utilization of a-hemihydrate gypsum is greatly limited. In this study, the effect of soluble

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