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gypsum dehydration volume in Oman
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Effect of carboxymethylcellulose on gypsum re-hydration …
The number of nuclei per solution volume unit influences the microstructure growth rate and crystal size ... An illustrative diagram of the steps from dihydrate dehydration up to hemihydrate hydration is shown in Fig. 1. ... Representation of the gypsum dehydration process; dissolution crystallization and hardening of the …
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Physicomechanical Properties of Gypsum with Mineral …
This work has investigated the possibility of two common minerals (silica flour and talc powder) in modifying composite gypsum's physical and mechanical …
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Review of gypsum reinforced composites as building materials
Heating beyond 190–200 °C results in the complete dehydration of gypsum rock, yielding CaSO 4, commonly referred to as gypsum anhydrite [6,7,8,9] due to the loss of crystallization water. The hemihydrate phase (CaSO 4 ⋅2H 2 O) can take two crystalline structures, alpha or beta, contingent upon the calcination method during manufacturing.
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Gypsum | Properties, Formation, Uses and …
Dehydration: One of the most notable chemical properties of gypsum is its ability to undergo controlled dehydration when heated. When gypsum is subjected to heat, typically at temperatures ranging …
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Ingenious approach for retrieving valuable metals from gypsum …
Section snippets Materials. Pristine Cr(VI)-containing gypsum was collected from the chlorate industry in Inner Mongolia, China. Following purification of the pristine samples, only CaSO 4 ·2H 2 O was found in the phase of the Cr(VI)-containing gypsum (Figure S1). The form of Cr(VI) is CrO 4 2-, which is supported by X-ray Photoelectron …
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Experimental Study on Physical and Mechanical Properties of Gypsum …
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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Understanding gypsum in 3 diagrams
Diagram 1 - Dehydration. The first process is the formation of hemihydrate or anhydrite from dihydrate. To obtain more information about this step, gypsum crystals were grown from sodium sulphate and calcium chloride via a diffusion process. A large test tube, approximately 200mL in volume, was filled with 3g of sodium sulphate (Na 2 SO 4).
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Dehydration‐induced damage and deformation in …
Gypsum undergoes brittle-ductile transition at moderate pressure (around 10 to 20 MPa confining pressure [Brantut et al., 2011]) …
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Dehydration Pathways of Gypsum and the Rehydration Mechanism of Soluble
The dehydration products of gypsum under different temperature and water vapor pressure were investigated by thermodynamic theory. ... CaSO4•0.5H2O) to gypsum (CaSO4•2 H2O), accompanied with a ...
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Gypsum Manufacturer & Supplier Oman|Marble, Limestone …
Established in 2010, GLOBAL GYPSUM BOARD CO LLC is the first to operate gypsum board and value added plaster plants in the Sultanate of Oman, with production capacities of 15 Million sqm for 12.5mm thicknesss plasterboards, 60,000 MT/year of value added plaster and 150,000 MT/year stucco production capacity.
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Dehydration Pathways of Gypsum and the Rehydration …
Prasad et al. 16 and Carbone et al. 17 investigated the dehydration mechanism of gypsum using in situ micro-Raman and energy-dispersive XRD, respectively, and concluded that γ-CaSO 4 was first obtained in the gypsum dehydration process, and then the formed γ-CaSO 4 was transformed into β-CaSO 4 ·0.5H 2 O by a …
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Study of Gypsum Dehydration by Controlled Transformation …
The dehydration of gypsum (CaSO 4 ·2H 2 O) into calcium sulfate hemihydrate (CaSO 4 ·0.5H 2 O) and anhydrites ( γ-CaSO 4 and β-CaSO 4 ) was carried out by heating under a constant pressure of water vapor using Controlled transformation Rate Thermal Analysis. No intermediate formation of calcium sulfate hemihydrate occurred under a …
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Kinetics of gypsum dehydration at reduced pressure: an …
Gypsum (CaSO4˙2H2O) dehydration kinetics were investigated through energy dispersive X-ray diffraction (EDXD), under reduced pressure (100 Pa), in the temperature range 313-353 K. The process follows the …
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Dissolution and conversions of gypsum and anhydrite
Calcium sulfate occurs in nature mainly in form of three different minerals distinguished by their degree of hydration: gypsum (CaSO 4 ), bassanite (CaSO 4 ⋅0.5H 2 O) and anhydrite (CaSO 4 ...
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Predicting Depths of Gypsum Dehydration in Evaporitic …
The conversion of gypsum to anhydrite upon burial and heating is accompanied by about a 39% volume decrease, a four-fold increase in thermal conductivity, and consumption of heat. Accurate "back-stripping" of an evaporite basin and tracking its thermal evolution requires a knowledge of the depth of the gypsum …
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Structural evolution during the dehydration of gypsum …
It is found that the dehydration of gypsum to anhydrite proceeds via the hemihydrate and γ-anhydrite phases and the interplay and behaviour of these phases …
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Dehydration-induced damage and deformation in …
during experimental dehydration of lizardite and gypsum. [3] Two challenging problems encountered in addressing the possible importance of dehydration embrittlement in ... At standard thermodynamic conditions, the molar volume of gypsum, bassanite, and water are 74.7, 53.8, and 18 cm3/mol, respectively [Robie et al., 1979]. Considering the ...
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Thermal behaviour and kinetics of dehydration of gypsum …
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 …
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A 4D view on the evolution of metamorphic …
We analyse the dehydration of gypsum to form bassanite and H2O which, like most dehydration reactions, produces a solid volume …
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Development of a solid reaction kinetics gypsum dehydration …
Gypsum plasterboard wall assemblies are extensively used as cladding material for walls, floors and ceilings, as well as a means for passive fire protection of timber structures. The good fire resistance characteristics of gypsum plasterboards are mainly owed to the gypsum "dehydration" process, occurring between 80°C and 250°C, where large …
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(PDF) The dehydration kinetics of gypsum at high
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 ...
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Thermo-poro-mechanics Modelling of Gypsum …
Thermo-poro-mechanics Modelling of Gypsum Dehydration 179 1 mol of gypsum Intact Gyp- sum Sample 1 mol of bassanite porosity 1.5 mol of water Reaction products excess Expelled w ater Fig.1. Illustration of the reaction (1) of gypsum into bassanite and water after a temperature increase up to 388oK. 1mol of Gypsum (molar volume 74.69cm3 …
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From atom level to macroscopic scale: Structural mechanism …
First study of gypsum single crystal dehydration using X-ray absorption tomography. Evidence and mechanism of a multi-scale crack pattern due to structure …
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Structural evolution during the dehydration of …
(a) Unit-cell volume of the hemihydrate phase during the dehydration study of pure gypsum within a sealed capillary with an excess of water. (b) View of the ab plane of the hemihydrate structure with 0.5 water …
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Formation of α-Hemihydrate Inside of a Gypsum …
Gypsum (calcium sulfate dihydrate) is one of the most used inorganic binding materials in the world. During calcination, calcium sulfate subhydrates are formed and, for technical reasons, are mixed with water …
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Fast in-situ X-ray scattering reveals stress sensitivity of …
Dehydration of axially pre-stressed, heated discs of natural gypsum rock (Volterra alabaster) was monitored in a purpose-built loading cell while collecting 2D …
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The crystallization water of gypsum rocks is a relevant …
Gypsum (CaSO 4 ·2H 2 O) is a rock-forming mineral that also occurs in soil 1.Gypsum outcrops are widespread throughout the Earth, being present in the five continents 2.They are particularly ...
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Experimental VNIR reflectance spectroscopy of gypsum dehydration
Volume 97, Number 4. April 2012 . Previous Article; Next Article; Article Contents. Article Navigation. ... The spectral behavior of gypsum dehydration in the visible to near-infrared (350–2500 nm) wavelength range was investigated by partially dehydrating the four main habits of gypsum (alabaster, satin spar, selenite, and massive) to form ...
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The dehydration process of gypsum under high …
ture at which the dehydration events occur increases (T dehydration = 425.5 K in an open system, T dehydration = 439 K in a sealed system, in the presence of excess water). Compared with the wealth of high-temperature studies available, there is a lack of experimental studies on the gypsum-anhydrite dehydration reaction sequences at
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Gypsum hydration: a theoretical and experimental study
Where φg is the volume fraction of gypsum, m hydration degree, vh/vw the specific volume ratio of hemihydrate/free water (0.36 for α- and 0.38 for β-hemihydrate), vn/vw the specific volume ratio of crystal water/free water (0.81 for α- and 0.71 for β-hemihydrate), w the water/hemihydrate ratio, and w0 the water requirement for the
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A 4D view on the evolution of metamorphic dehydration reactions …
We analyse the dehydration of gypsum to form bassanite and H2O which, like most dehydration reactions, produces a solid volume reduction leading to the formation of pore space.
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Kinetics of gypsum dehydration at reduced pressure: an …
Gypsum (CaSO 4 ·2H 2 O) dehydration kinetics were investigated through energy dispersive X-ray diffraction (EDXD), under reduced pressure (100 Pa), in the temperature range 313–353 K. The process follows the JMAK (Johnson-Mehl-Avrami Kinetic) model. The fitting procedure of the Arrhenius expression provides an activation …
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Experimental Study on the Properties and Hydration Mechanism of Gypsum
In order to achieve the resourceful, large-scale and high-value utilization of bulk industrial solid wastes such as flue gas desulfurization gypsum (FGDG), fly ash (FA) and ground blast furnace slag (GGBS), and to reduce the dosage of cementitious materials, orthogonal experimental methods were used to prepare composite cementitious …
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In situ IR spectroscopic and thermogravimetric study of the dehydration …
The dehydration of gypsum CaSO 4.2H 2 O has been studied, at negligible water vapour pressure, by in situ infrared (IR) spectroscopy and by thermogravimetry to determine whether intermediate phases (CaSO 4. n H 2 O) exist, other than the hemihydrate with n =0.5, and also to compare the mechanism of the dehydration process when measured …
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Effect of high temperatures on gypsum-based composites
Section snippets Thermo-chemistry of used materials. Calcined gypsum (commonly known as a Plaster of Paris) in powder form consists mainly of calcium sulphate hemihydrate CaSO 4 ·1/2H 2 O, which is prepared by dehydration of calcium sulphate dihydrate CaSO 4 ·2H 2 O (natural gypsum rock or an industrial by-product, e.g. from …
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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 an externally heated diamond anvil cell. At 2.5 GPa, gypsum starts to dehydrate around 428 K, by forming bassanite, CaSO4 hemihydrate, which completely …
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