Reagent grade gypsum was dehydrated at 85 °C for 144 h in order to get pure bassanite und at 550 °C for 16 h in order to obtain pure anhydrite II (Table 1). ...
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Etymology and history. The word gypsum is derived from the Greek word γύψος (gypsos), "plaster". [9] Because the quarries of the Montmartre district of Paris have long furnished burnt gypsum (calcined gypsum) used for various purposes, this dehydrated gypsum became known as plaster of Paris.Upon adding water, after a few dozen minutes, plaster of Paris becomes …
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1. Ultrasonic results indicate gypsum hydration reaction consists of two stages: the dissolution of hemihydrate in the first stage and the nucleation and precipitation of dihydrate in the second stage. 2. Gypsum hydration is strongly influenced by water amount. Spread flow test is suitable to determine the water demand for gypsum hydration.
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Various faces of dehydrated gypsum-cleaved blocks and single crystals have been investigated using optical microscopy, SEM, and TEM. The orientation of the cracks with respect to the initial gypsum structure and the Miller indices of all possible crack planes have been determined. These crack planes have been found to be few and to correspond ...
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The surface character of the dehydrated gypsum was analyzed in SEM, additionally. It is obvious that the layer's burst and broken parts and cracks are formed at the surface. The surface of the hemihydrate is much larger than that of the dihydrate crystal. Formed cracks are shown in Figure 5a,b. Larger, cross-like cracks can be observed beside ...
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In gypsum, the structure is layered, parallel to the b direction. Tetrahedral SO 4 anions are linked by Ca cations as chains parallel to c, which form as double sheets interlayered with sheets of water molecules. Dehydrated forms of gypsum range isostructurally from CaSO 4 ·2H 2 …
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Dehydration of axially pre-stressed, heated discs of natural gypsum rock (Volterra alabaster) was monitored in a purpose-built loading cell while collecting 2D small- and wide …
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The dehydration products of gypsum under different temperature and water vapor pressure were investigated by thermodynamic theory. Additionally, the rehydration mechanism of soluble anhydrite...
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TACKTILE Gypsum Skimming Plaster 40Kg SKU: PL40TACK1 Tacktile Gypsum Skimming Plaster is a high-quality interior finishing product designed for easy application. Simply mix the powder with clean water for a consistent, creamy slurry. This lightweight plaster is made from dehydrated gypsum mineral and sets by chemically recombining with water. It's versatile, …
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Dehydrated gypsum: Plaster of Paris: CaSO4·1/2H2O: Partially dehydrated gypsum: Gypsum is an important mineral with a wide range of applications. Its chemical formula, CaSO4·2H2O, represents its unique composition and properties. Understanding the properties and uses of gypsum can help us appreciate its significance in various industries.
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Gypsum is an anisotropic hydrous mineral found abundantly in fold-thrust belts along with its dehydrated forms (bassanite and anhydrite). Because gypsum contains water in its structure, it can accommodate large shear deformation under external load.
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The obtained dehydrated gypsum contained combined gypsum phases of dihydrate, hemihydrate, and II-anhydrite. Cao et al. [23] also found that the soluble phosphate content decreased after calcination at 500 °C. All the experimental results of previous researches have illustrated that the content of soluble phosphates in the dehydrated PG ...
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The dehydration of gypsum can be observed using thermo-gravimetric measurement and differential scanning calorimetry. Depending on the parameters of …
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Dehydration reactions have important effects on fluid flow, porepressure and brittle failure in the Earth.The rates and mechanismsof reaction are relevant to understanding those effects.The micro-structures ofa set ofsamples containing bassanite and gypsum fromdehydration experiments on Volterra gypsum have been analysed byconventional transmitted light …
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The microstructures formed by the dehydration of gypsum under controlled conditions of temperature and water vapor partial pressure were characterized using in situ X …
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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 ...
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Mass losses vary between 13.7 and 16.5% and heat of dehydration values between 377 and 420 J g −1 for the dehydration of ground and mixed inhomogeneous gypsum samples. As for the dehydration of CaSO 4 ·2H 2 O, the dehydration of synthetic gypsum proceeds via multi-step reactions. Using a heating rate of 5°C min −1, the very slow …
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The dehydration reaction of gypsum into bassanite and water induces a large porosity increase, which is partially compacted. The higher the effective stress, the larger the compaction. Application of a constant …
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An interplay between reaction progress and rock permeability becomes evident when one compares the molar volumes [e.g., Deer et al., 1992] of the educt and solid products involved in the transformation of gypsum (74.53 cm 3 /mol) to bassanite (53.17 cm 3 /mol) and anhydrite (45.68 cm 3 /mol), respectively. One notices that, at ambient conditions, the solid …
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Gypsum Mineral Description. Gypsum is a hydrated calcium sulfate with composition CaSO 4 ·2H 2 O. It commonly occurs as a chalky powder or occasionally as small crystals. In gypsum, the structure is layered, parallel to the b direction. ... Dehydrated forms of gypsum range isostructuraly from [CaSO 4 ·2H 2 O] to [CaSO 4]. The hemihydrate ...
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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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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 60 ml size and dehydrated in two different furnace types to cover the complete temperature range.The furnaces were calibrated with thermo elements.
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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 temperature range of …
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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 dehydrates to γ-anhydrite at 488 K. …
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This study could prove that it is possible to quantify bassanite and anhydrite III in samples of dehydrated gypsum by Rietveld refinement of XRD data especially in mixtures consisting of more than one calcium sulphate modification. Abstract. Technical OPC normally contains mixed sulphate carriers in varying amounts. Gypsum (calcium sulphate ...
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In our study, we employ microindentation tests to examine the micromechanics of gypsum during dehydration. We found that the pre-dehydrated gypsum deforms through …
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and that the unaltered gypsum in the core is very dense. Finally, the SEM cross section in Figures 1e and 1f (Sample 7, 398 K) highlights the transition from the porous rim to gypsum this time containing dispersed bassanite fibers. [12] The absence of bassanite in the gypsum core of all samples dehydrated at 388 K and its concurrent occurrence
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We report on changes in rock permeability induced by devolatilization reactions using gypsum as a reference analog material. Cylindrical samples of natural alabaster were dehydrated in air (dry ...
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Rebecca C. Hildyard, Sergio Llana-Fúnez, John Wheeler, Daniel R. Faulkner, David J. Prior, Electron Backscatter Diffraction (EBSD) Analysis of Bassanite Transformation Textures and Crystal Structure Produced from Experimentally Deformed and Dehydrated Gypsum, Journal of Petrology, Volume 52, Issue 5, May 2011, Pages 839–856, https://doi ...
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This was also observed by Hamad [21] by the study on the image and lattice of a dehydrated gypsum by electron microscope. 3.1. Absorption bands of water molecule [22–24] The presence of water in a sample can be detected by its two characteristic absorption bands in the 3600–3200 cm −1 region and in the 1650 cm −1 region.
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DOI: 10.1016/J.CEMCONRES.2009.06.018 Corpus ID: 96616635; Quantitative Determination of Anhydrite III from Dehydrated Gypsum by XRD @article{Seufert2009QuantitativeDO, title={Quantitative Determination of Anhydrite III from Dehydrated Gypsum by XRD}, author={Sebastian Seufert and Christoph Hesse and Friedlinde Goetz-Neunhoeffer and …
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GASES UPON DEHYDRATED GYPSUM Robert F. Benson1 and George D. Blyholder Department of Chemistry, University of Arkansas, Fayetteville, Arkansas 72701 ABSTRACT: This work explores surface interactions between gypsum and selected prominent gaseous emissions in to the atmosphere. Gypsum is a common air-borne mineral particulate that has a potential
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temperature dehydrated gypsum rock was treated with different hydration time, and the gypsum rock samples in three states were subjected to ultrasonic test, density test and uniaxial compression test. The results show that the main components of natural gypsum minerals were gypsum dihydrate (71%), dolomite (27%) and potassium chloride (2%). The
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