Utilization of Phosphogypsum to Synthesis Α-Hemihydrate Gypsum …
A brand new method to transform flue gas desulfurization gypsum (FGD gypsum) into α-calcium sulfate hemihydrate (α-HH) with short hexagonal prisms mediated by succinic acid disodium salt ...
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(PDF) Eco‐balance features and significance of hemihydrate
Eco‐balance features and significance of hemihydrate phosphogypsum reprocessing into gypsum binding materials. ... Early age (2 h) strength of binder was from 0.1 to 15 MPa and after 14 d ...
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The Influences of Soluble Phosphorus on Hydration Process …
The application of α-hemihydrate gypsum (α-HH) is limited by several factors, such as a rapid hydration rate, short setting time, poor water resistance, and high cost.
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Calcium sulphate hemihydrate hydration leading to gypsum
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 Crystal …
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Formation of α-Hemihydrate Inside of a Gypsum Crystal …
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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The Science of Plaster of Paris: How It Works and Why It's So …
It is a type of gypsum plaster that is made by heating gypsum to a high temperature and then grinding it into a fine... Email info@gypsonaplaster / Phone +91 - 9711 866 263. Gypsum Plaster Manufacturers Rajasthan ... The chemical composition of plaster of Paris is calcium sulfate hemihydrate, which means that it contains about half as much ...
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Utilization of low-quality desulfurized ash from semi-dry …
Calcium sulfate hemihydrate whiskers (CSHW), a multi-functional and high value-added building material, were prepared with flue gas desulfurization (FGD) gypsum by hydrothermal method, which could ...
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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 to …
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Structures of a) gypsum, b) hemihydrate, and c) …
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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The influence of calcium formate on the hydration of calcium …
The gypsum saturation index started at 0.7 but then drops to a relative equilibrium at 0.1 after 30 min. When CF was present, the saturation index values of hemihydrate and gypsum were initially similar to the sample without CF. However, they remained at high values (− 0.1, and 0.7, respectively) for a longer period of time.
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Experimental research on desulfurization gypsum with …
Pouring time should be controlled in the time before α-hemihydrate decorative gypsum hydration, and the pouring temperature can be slightly lower than the autoclave temperature.
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Effect of Fluorine and Phosphorus Impurities in …
In this study, phosphogypsum (PG) is simulated by doping fluorine and phosphorus ions in an analytically pure reagent of gypsum dihydrate. The influence of fluorine and phosphorus impurity and content on the dehydration reaction process of phosphogypsum and its crystalline micromorphology is assessed during the preparation of α-type gypsum …
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Experimental Study and Mechanism Analysis of Preparation …
Flue-gas desulphurization (FGD) gypsum is a highly prevalent industrial by-product worldwide, which can be an excellent alternative to natural gypsum due to its high content of CaSO4·2H2O. The preparation of α-calcium sulfate hemihydrate is a high-value pathway for the efficient use of FGD gypsum. Here, a dynamic method, or an improved …
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Calcium Sulphate Hemihydrate Hydration Leading to Gypsum
The hydration of calcium sulphate hemihydrate (CaSO4·0.5H2O) leading to the crystallization of gypsum (calcium sulphate dihydrate – CaSO4·2H2O) has been the subject of several investigations ...
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Synthesis of calcium sulfate hemihydrate whiskers from high …
Calcium sulfate hemihydrate whiskers (CSHWs) were prepared from high-purity salt gypsum in a glycerol–water system. The effects of the glycerol/water ratio, reaction temperature, reaction time, and stirring speed on the crystal …
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Effect of Soluble Phosphorus on the Mechanical …
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 phosphorus on the setting time and mechanical properties of a-hemihydrate gypsum was investi-gated by adding different amounts of H 3PO 4 ...
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α-Calcium Sulfate Hemihydrate Preparation from FGD Gypsum …
7 Even though six different gypsum phases are reported, only anhydrous gypsum (CaSO 4 ), hemihydrate gypsum (CaSO 4 ·0.5H 2 O) and dihydrate gypsum (CaSO 4 ·2H 2 O) are commonly found in the ...
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Production and properties of the polyvinyl alcohol modified …
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 SEM, XRD, TGA …
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α-calcium sulfate hemihydrate preparation from FGD gypsum …
The FGD gypsum produced from Xiaoshan Power Plant (Zhejiang Province, China) was adopted as raw material. The chemical composition is presented in Table 1. FGD gypsum is mainly composed of DH, with a purity of 94.23%. Some traces of heavy metals, 1.3 mg kg −1 Hg and 6.3 mg kg −1 Cr, are found in the FGD gypsum.
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Plaster of Paris | Formula, Properties & Application
Scientifically known as Calcium Sulfate Hemihydrate, Plaster of Paris is chemically represented as CaSO 4.1/2H 2 O. This represents the ratio of calcium sulfate to water, suggesting that for each molecule of calcium sulfate, there is half a molecule of water. ... It is formed by the partial dehydration of gypsum, a mineral composed of calcium ...
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What is the Difference Between Alpha and Beta Hemihydrate
The process of converting gypsum into alpha hemihydrate involves heating gypsum at a specific temperature to remove water molecules, resulting in a more concentrated and stable form of calcium sulfate. The term "alpha" in alpha hemihydrate refers to the unique crystal structure formed during this dehydration process. The alpha form exhibits ...
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No. 4710 February 6, 1960 NATURE 375
thermal analysis in a sample of hemihydrate prepared by calcining gypsum under conditions simulating the manufacture of gypsum plaster in a kettle. By means of differential thermal analysis it is ...
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Plaster of Paris: Past, present and future
Plaster of Paris is calcined gypsum (roasted gypsum), ground to a fine powder by milling. When water is added, the more soluble form of calcium sulphate returns to the relatively insoluble form, and heat is produced [2 (CaSO 4 …
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Crystallization Kinetics of α-Hemihydrate Gypsum Prepared …
α-Calcium sulfate hemihydrate (α-HH) is an important cementitious material, which can be prepared by hydrothermal method from calcium sulfate dihydrate (DH) in an electrolyte solution. Study of the conversion kinetics of DH to α-HH in NaCl solution is helpful for understanding the control process. In this paper, X-ray diffraction (XRD) patterns were applied …
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Microstructure and mechanical properties of β-hemihydrate …
Some of the most important materials in the building industry is CaSO 4 ·2H 2 O, called gypsum (calcium sulfate hydrate), which is necessary for sound insulation at walls, in addition to many ...
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Understanding gypsum in 3 diagrams
There are three main diagrams that can help us understand this cycle in detail. The first describes the process of water leaving the structure of gypsum to form hemihydrate or anhydrite. The second depicts the temperature-dependent solubility of the calcium sulphates …
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New insight into the phase changes of gypsum
The temperature at which the gypsum binder (calcium sulfate hemihydrate) is industrially produced, between 80 and 180 °C, is often mentioned in the literature …
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Crystallization kinetics of large-sized columnar α-hemihydrate gypsum …
In 2019, the USGS [6] reported that the estimated amount of crude gypsum produced in the USA was 20 million tons while 17 million tons of gypsum was mined in the first three quarters of 2021, a rise of 9 % year-on-year from 15.6 million tons in the same period in 2020. China is the second largest producer of construction gypsum with annual ...
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Efficient extraction of impurities from phosphogypsum …
In this study, by regulating gypsum crystal and P species in CaCl 2 –HCl solutions under mild conditions, efficient removal of P impurities (leaching efficiency of 97.78%) and synchronous preparation of high-strength α-CaSO 4 ·0.5H 2 O (α-HH) (compressive strength of 35.2 MPa) from PG were achieved during the phase transition from CaSO 4 ...
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Insight into the influences of β-hemihydrate and dihydrate gypsum …
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 gypsum exhibit relatively higher solubility and dissolve more quickly than CaSO 4. However, there is little information on their incorporation in CAC.
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