Influence of the Calcination Temperature of Synthetic Gypsum on …

dehydration of natural gypsum stone (dihydrate calcium sulphate) from an opencast gypsum mine. It is characterized by the quick growth of mechanical strength and …

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Raman spectroscopy of the dehydration process of gypsums

dehydration of dihydrate and hemihydrate was carried out by Chang et al. (1999) using RS. ... another 13 h was adopted to investigate the gypsum dehydration in the temperature span …

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The dehydration process of gypsum under high pressure

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 …

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Gypsum board dehydration kinetics at autogenous water vapour …

Gypsum board dehydration takes place at the temperature range between ∼80 °C and 250 °C, depending on the heating rate and the composition of the gypsum board [1], [10], …

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Dehydration Pathways of Gypsum and the Rehydration …

In this work, the dehydration pathways of gypsum and the rehydration mechanism of soluble anhydrite were mainly investigated by thermodynamic modeling and MC …

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KINETIC STUDIES OF THERMAL DEHYDRATION OF …

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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Gypsum hydration: A theoretical and experimental …

These two experiments clarified that: i) increasing gypsum amount up to 4.5% of binder mass effectively reduced free shrinkage strain subjected to 30 degree of ambient temperature, ii) this free ...

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Dehydration behaviour and impurity change of phosphogypsum during

Dihydrate gypsum is the dominant phase composition in PG, it is a stable phase at room temperature but can be converted into α-hemihydrate gypsum ... PG was subjected to …

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Dehydration Temperature of Gypsum

(1) In an atomsphere, the primary dehydration temperature of natual dihydrated gypsum used as a test sample is 133°C while its secondary dehydration temperature being 192°C.

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Structural evolution during the dehydration of gypsum materials

Structural evolution during the dehydration of gypsum materials - Volume 73 Issue 3 ... Jorgensen, J.D. and Hinks, D.G. (1984) A crystallographic study of the low-temperature …

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dehydration temperature of gypsum dihydrate in Oman

The dehydration mechanism of natural single crystals of gypsum was investigated in the temperature range 300-430 K by in situ infrared (FTIR) spectroscopy. The thermal evolution of …

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Formation of α-Hemihydrate Inside of a Gypsum …

During calcination, calcium sulfate subhydrates are formed and, for technical reasons, are mixed with water to form dihydrate again. Therefore, the dehydration process of gypsum and the ...

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Problem 146 Gypsum on heating gives: (a) ... [FREE …

Gypsum is chemically known as calcium sulfate dihydrate, represented by the formula ( mat{CaSO}_4 cdot 2 mat{H}_2 mat{O} ). ... 02 Dehydration of Gypsum. When …

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Dihydrate gypsum dehydration temperature

Gypsum dihydrate Big Chemical Encyclopedia. Soluble anhydrite is readily made from gypsum by dehydration at temperatures of 140—200°C Insoluble anhydrite can be made by beating the …

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(PDF) Dehydration Pathways of Gypsum and the …

The thermodynamic calculation results reveal that the dehydration mechanism of gypsum significantly depended on ambient temperature and water vapor pressure.

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Laboratory Scale Study of Calcium Sulfate Hydration Forms

This thesis examines the dehydration and rehydration behavior of calcium sulfate hydration forms using thermal and microscopic techniques. Thermogravimetric analysis was used to study the …

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What are the properties of building gypsum?

The hydration product of gypsum is dihydrate gypsum, while the dehydration temperature of dihydrate gypsum is low, about 120 ℃. When the air humidity is low, the dihydrate gypsum …

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Structures of a) gypsum, b) hemihydrate, and c) insoluble …

As can be seen in Fig. 11 the dehydration temperature of the hemihydrate increases with sodium content. ... which can be found as calcium sulfate dihydrate or gypsum (CaSO 4 ⋅2H 2 O ...

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Dissolution and conversions of gypsum and anhydrite

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. ... dihydrate: Jour. Inorg. …

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Gypsum hemihydrate–cement blends to improve renderings …

The reactivity of gypsum-based binders is produced by gypsum (dihydrate) (CaSO 4 ·2H 2 O) dehydration. Depending on dehydration temperature, vapor pressure inside of …

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Dihydrate gypsum dehydration temperature

Dehydration behaviour and impurity change of phosphogypsum during. Dihydrate gypsum is the dominant phase composition in PG, it is a stable phase at room temperature but can be …

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Discrimination of bassanite and anhydrite III dehydrated from …

Gypsum (calcium sulphate dihydrate, CaSO4 ·2 H2O) is added to the clinker before the mill-ing process and dehydrates partially to bassanite (calcium sulphate hemihydrate, CaSO4 ·0.5 …

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Thermal Analysis of Calcium Sulfate Dihydrate and Supposed

a-CaSO •. 1/2H20 had lower peak and first-break temperatures than that of the {3-form. The peak ... in the complete dehydration of CaSO •. 2H20 was supported by the results of ... thermal …

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Calcium sulphate hemihydrate hydration leading to gypsum

The hydration of calcium sulphate hemihydrate (CaSO 4 ·0.5H 2 O) leading to the crystallization of gypsum (calcium sulphate dihydrate – CaSO 4 ·2H 2 O) has been the subject …

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Application: Thermal analysis of gypsum

The two-stage dehydration of calcium sulphate dihydrate occurs between 100 °C and 300 °C. The first step is the formation of hemihydrate (CaSO4 ∙ 2H 2 O to CaSO 4 ∙ ½H 2 O). A further dehydration forms the anhydrate (CaSO 4 ½H 2 …

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(PDF) The thermal dehydration of natural gypsum and pure …

However only - 35% of natural gypsum is calcium sulphate dihydrate. Thus on calculating, 35% of the heat of dehydration of the calcium sulphate dihydrate value gives a heat of dehydration of …

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Dehydration Pathways of Gypsum and the Rehydration Mechanism …

The dehydration products of gypsum under different temperature and water vapor pressure were investigated by thermodynamic theory. Additionally, the rehydration mechanism …

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Dehydration behaviors and properties of anhydrite II prepared by

The addition of sulfuric acid reduced the dehydration temperature, accelerating the nucleation of anhydrous calcium sulfate and increasing the number of crystal nuclei, resulting …

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Overlay of gypsum DSC curves obtained with open …

The crystal structure of the grown crystals was confirmed to be very similar to that of calcium sulfate dihydrate (CaSO4·2H2O, gypsum). The temperature at which dehydration and evaporation of ...

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The thermal dehydration of natural gypsum and pure calcium sulphate

However only - 35 % of natural gypsum is calcium sulphate dihydrate. Thus on calculating, 35% of the heat of dehydration of the calcium sulphate dihydrate value gives a …

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Synthesis of large plate-like gypsum dihydrate from waste gypsum …

Dehydration of gypsum dihydrate to gypsum hemihydrate in liquid phase can be understood in terms of solubility. The cross point of solubility of gypsum dihydrate and …

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Thermal Analysis of Calcium Sulfate Dihydrate and Supposed

As a part of the continuing study of gypsum plaster 1 the properties of calcium sulfate dihydrate ... The gaseous pressures within the DTA cell were plotted versus the peak temperatures for the …

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Quantitative determination of anhydrite III from dehydrated gypsum …

Gypsum (calcium sulfate dihydrate, Fluka, 99.9% purity) samples were dehydrated at temperatures from 85 up to 800 °C 25 g of substance was weighed in corundum crucibles of …

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What is the formation process of hemihydrate in gypsum?

The formation process of hemihydrate in gypsum primarily involves the dehydration of calcium sulfate dihydrate (CaSO₄·2H₂O) through heating. This process can be observed in two main …

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(PDF) Experimental Study on Physical and Mechanical

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 …

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Discrimination of bassanite and anhydrite III dehydrated from …

Gypsum (calcium sulphate dihydrate, CaSO4 ·2 H2O) is added to the clinker before the mill-ing process and dehydrates partially to bassanite ... Sample Name Time of dehydration …

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