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Using solar energy to dehydrate gypsum to produce β-hemihydrate is one way to improve the carbon footprint 13,14 . Alternatively, α-hemihydrate is produced from gypsum using an autoclave process ...
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DOI: 10.1016/j.jcrysgro.2021.126360 Corpus ID: 241731164; Preparation of hemihydrate gypsum with controllable morphology in Glycerol-NaCl-Water solutions with maleic acid @article{Chen2021PreparationOH, title={Preparation of hemihydrate gypsum with controllable morphology in Glycerol-NaCl-Water solutions with maleic acid}, …
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1. Introduction. Gypsum is a material in which the amount of water of crystallization varies with its surrounding conditions, such as temperature or humidity, and can be classified into three groups, namely, calcium sulfate anhydrite (CaSO 4), calcium sulfate hemihydrate (CaSO 4 ∙1/2H 2 O), and calcium sulfate dihydrate (CaSO 4 ∙2H 2 …
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Flue gas desulfurization (FGD) gypsum, which is mainly composed of DH, was used as raw material to obtain α-HH through dehydration in a Ca–Mg–K–Cl-solution medium at 95°C under atmospheric pressure.
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During hemihydrate gypsum hydration, the proportion of free P was higher, which mainly existed as H3PO4 and H2PO4⁻, but P species on dihydrate gypsum surface contained a higher HPO4² ...
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Gypsum and anhydrite are naturally occurring minerals, however the hemihydrate and anhydrite can be obtained by calcination which is a process of chemical alteration by …
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Flue gas gypsum may be converted to α-hemihydrate by suspending the starting material in inorganic salt solutions of high concentration or in diluted sulfuric acid and maintaining the suspension at boiling, or near boiling temperature for a period of time. The crystal morphology of the produced α-hemihydrate gypsum and, thus, its quality …
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Here we report a facile and cost-effective wet-chemical approach to the synthesis of calcium sulfate hemihydrate nanowires (HH NWs, CaSO4·0.5H2O), and their robust performance in immobilizing water molecules to the crystal lattice of CaSO4 and then separating them from a surfactant-stabilized water-in-oil emulsion (mean droplet size of …
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The mass loss in the temperature range of 81.6 ℃∼137.1 ℃ is caused by the dehydration of gypsum into hemihydrate gypsum, which is in accordance with ref [40]. As the temperature continues to increase to 297.5 °C, the mass loss reaches 5.80 %. This is the result of the removal of crystal water from hemihydrate gypsum and omongwaite.
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Mexico). Gypsum is one of the softest min-erals and one of the rst minerals to crystal-ize as seawater evaporates. Thus, gypsum is ... The slurry form of hemihydrate gypsum …
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The gypsum crystal system is monoclinic, and gypsum usually occurs in soils as masses of crystals with acicular, lenticular, tabular, prismatic, rosette, and …
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The polyvinyl alcohol (PVA) reinforced macro-defect-free α-hemihydrate gypsum composite (PMC) was prepared by compression molding technique. The mechanical strength from the age of 3 d to 120 d and water resistance of PMC were tested, and the phase composition, microstructure, pore structure of PMC was characterized by …
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Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate (CaSO4·2H2O). It is commonly found in sedimentary rock formations and is often …
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Gypsum hydration: a theoretical and experimental study. Calcium sulphate dihydrate (CaSO4·2H2O or gypsum) is used widely as building material because of its excellent …
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The White Sands National Monument in New Mexico is known for its vast dune fields of pure gypsum sand. Mexico: Mexico has significant gypsum deposits, particularly in the states of Nuevo León, Chihuahua, and Coahuila. Canada: Gypsum deposits are found in provinces like Nova Scotia, Newfoundland and Labrador, and …
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The applications of gypsum in China are primarily twofold: the preparation of high-strength gypsum, construction gypsum, composite cementing materials, and others, and the preparation of gypsum building products like gypsum board and gypsum blocks. Among these, α-hemihydrate gypsum (α-HH) is a high-end gypsum product, mainly …
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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 to form dihydrate again. Therefore, the dehydration process of gypsum and the rehydration of hemihydrate were investigated. This …
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An industrially feasible process was proposed to produce α-calcium sulfate hemihydrate (α-HH) from FGD gypsum without any additives. In this process, an AlCl 3 solution was used to promote the …
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CAH 10 and C 28 are the main hydration products in CAC and they are responsible for its high strength at the early age [9]. ... Dihydrate and β-hemihydrate …
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The apparent empirical activation energies (Ea) suggest that the transition from gypsum to hemihydrate is mainly controlled by nucleation and growth mechanism, while the transition from gypsum to γ-anhydrite is mostly followed by phase boundary mechanism. ... Impact of limestone fineness on cement hydration at early age. Cement …
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Then, the hemihydrate slurry is hydrated to dihydrate under specific process conditions of temperature and acidity defined by Prayon. Dihydrate slurry is filtered on a Prayon tilting pan filter to recover a high-quality …
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Hemihydrate gypsum is found in two forms: α-hemihydrate gypsum (α-CaSO 4 ⋅0.5H 2 O) and β-hemihydrate gypsum (β-CaSO 4 ⋅0.5H 2 O) [8]. The α-hemihydrate gypsum is produced by the autoclaving and salt solution method whereas β-hemihydrate gypsum is obtained through calcination at temperature lower than 200 °C. …
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The current mapped extent of gypsum soils in the United States, based on the Gridded SSURGO (gSSURGO) product (Soil Survey Staff, 2013), indicates a total of 10,916 km 2 (Figure 1).For this compilation, "gypsum soils" are considered to include soil map units in which "gyp" is included in the taxonomic classification of the named soil …
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Beta hemihydrate is formed when gypsum is heated up to around 100°C in a normal open kettle or rotary kiln. Alpha hemihydrate is formed in an autoclave above 100°C in a water (suspension autoclave) or in a steam autoclave. 5 - 7 This is possible …
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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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DOI: 10.1016/J.PCRYSGROW.2007.01.002 Corpus ID: 96747728; Calcium sulphate hemihydrate hydration leading to gypsum crystallization @article{Singh2007CalciumSH, title={Calcium sulphate hemihydrate hydration leading to gypsum crystallization}, author={Nakshatra Bahadur Singh and Bernhard Middendorf}, journal={Progress in …
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Theoretically, hydrogen would be the better option, because it is only bounded in the water in gypsum and hemihydrate and oxygen is also bounded to sulfur in the sulfate. A new piece of the crystal was stored for a shorter time (around 30 min) at 140 C and prepared in the same way as for the experiments shown in Figure 6a,b, leading to an ...
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DOI: 10.1016/j.powtec.2024.119857 Corpus ID: 269876963; Synthesis of calcium sulfate hemihydrate whiskers from high-purity salt gypsum in a glycerol–water solution at atmospheric pressure
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Phosphogypsum can be used to prepare β-hemihydrate gypsum (β-CaSO4·1/2H2O) plaster. A prerequisite for any effective reuse of phosphogypsum is to understanded the act by which impurities in ...
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Calcium sulfate occurs in nature in form of three different minerals distinguished by the degree of hydration: gypsum (CaSO4·2H2O), hemihydrate (CaSO4·0.5H2O) and anhydrite (CaSO4).
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