Phosphogypsum (PG) is a massive industrial solid waste. In this paper, PG was purified by flotation method, and α-hemihydrate gypsum (α-HH) was prepared by the autoclaving method. The morphology ...
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Difference Between Gypsum and Anhydrite Gypsum vs Anhydrite Gypsum, also called hydrated calcium sulphate (CaSO4 · 2H2O) and anhydrite (CaSO4), also called hydrous calcium sulphate are the major minerals in the sedimentary rocks of rock gypsum and rock anhydrite respectively. Gypsum consists of calcium, sulfur and …
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Calcium sulfate. J L RICCI, ... H ALEXANDER, in Bioceramics and their Clinical Applications, 2008. 14.2.1 Gypsum and its derivatives. CS cements begin as gypsum, or calcium sulfate dihydrate (CaSO 4 · 2H 2 O), which is either mined from the earth or produced through more controlled chemical processes (Randolph, 1971).Gypsum and …
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Gypsum is softer, whereas anhydrite is a hard crystal. The hardness rating of gypsum is about 2, while If we look at its hardness rating of anhydrite, then it is 3.5. The density of gypsum is about 2.33g/cc, whereas the density of anhydrite is 3.2g/cc. Gypsum has a monoclinic structural form, while anhydrite has an orthorhombic structural form.
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GA has two carboxyl groups, while TA and CA have three carboxyl groups. The difference between TA and CA is that CA has one more hydroxyl group at the middle carbon atom than TA. α-HH gypsum has a hexagonal prismatic crystal form (Fig. 1 c), and in the absence of crystal modifiers, the crystal grows fastest along the c-axis [32].
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2. With the continuous progress of hydration, β-type hemihydrate gypsum produces more and more colloidal particles of dihydrate gypsum. These particles are smaller than the original, have a large specific surface area, and absorb a lot of water; they continue to be hydrated and evaporated.
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Calcium sulfate exists in three forms, namely dihydrate or gypsum (CaSO4·2H2O), anhydrite (CaSO4), and hemihydrate or bassanite (CaSO4·0.5H2O) depending on temperature, pressure, pH, and formation conditions. The formation of calcium sulfates occurs widely in nature and in many engineering settings. Herein, a …
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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 …
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The phase change of hemihydrate to dihydrate gypsum at different pH was followed by XRD. As shown in Fig. 10, the typical diffraction peak (2-theta = 14.82°, PDF card No. 41-0224) of hemihydrate was outstanding in early hydration time at all pH. It was about 30 min that the peak of hemihydrate disappeared in the reference sample.
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Fig. 1 shows the XRD pattern of FGD gypsum raw materials, which indicates that the main phase of FGD gypsum is calcium sulfate dihydrate. The morphology of FGD gypsum is given in Fig. 2.As illustrated in Fig. 2 a, the FGD gypsum has large particles with an average particle size distribution of about 60 μm. Fig. 2 b clearly reveals that …
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Gypsum and anhydrite are both minerals that are often used in plaster and construction. However, there is a big difference between these two minerals. Gypsum is a soft mineral that is composed of calcium sulfate dihydrate, while anhydrite is a hard mineral that is composed of calcium sulfate hemihydrate. Anhydrite takes longer to set than […]
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Calcium sulphate dihydrate (CaSO4·2H2O or gypsum) is used widely as building material because of its excellent fire resistance, aesthetics, and low price. Hemihydrate occurs …
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A microscope study has been made of the development of crystals of calcium sulphate hemihydrate produced on, or in, sheets of the dihydrate in the form of selenite by calcining under controlled conditions. The crystal forms were shown to be strongly dependent upon both temperature and ambient water vapour pressure. A mechanism for …
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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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Gypsum (calcium sulfate dihydrate) is burned to calcium sulfate hemihydrates or anhydrite to be used in different building materials. The hemihydrate …
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Anhydrite (CaSO 4) and gypsum (CaSO 4 ·2H 2 O) are the two most abundant minerals of ancient marine evaporite deposits and are also common in non-marine evaporite deposits. Sedimentary gypsum forms by direct precipitation out of evaporating seawater under arid climatic conditions in hydrologically restricted marine …
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Gypsum is a well-known mineral that is obtained from natural resources or from technological processes. Gypsum (calcium sulfate dihydrate) is burned to calcium sulfate hemihydrates or anhydrite to be used in different building materials. The hemihydrate and anhydrite...
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In this study, we investigated the influence of β-hemihydrate and dihydrate gypsum on the properties and phase conversion of white CAC.
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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 of several investigations over a long period and a vast amount of data is widely distributed throughout in the literature. In this review article an overall picture of the …
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1. Introduction. Gypsum is a widely applied green and recyclable material, and it is an indispensable and important cementitious material. As a non-structural material, gypsum can be utilized for floors, boards and wall-fillings [1], [2], [3], [4].When applied, hemihydrate gypsum (CaSO 4 ·0.5H 2 O) powder is mixed with water, which forms a …
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1 Introduction . Calcium sulfate hemihydrate [CaCO 4 ∙ 0.5H 2 O(s)] can be found naturally in very dry climate regions in Egypt, Australia, Death valley and Kuwait as bassanite, but in the presence of water or humid atmosphere it can convert to dehydrate [1, 2]. Therefore, the production of hemihydrate industrially has been studied widely through the dehydration …
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1. Introduction. Gypsum (CaSO 4 ·2H 2 O, also known as dihydrate) plaster is one of the earliest building materials elaborated by mankind, and gypsum plasterboard is used widely as indoor building material because of its easy fabrication feature, environmental friendliness, fire resistance, aesthetics, low price, etc. The global …
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Hemihydrate occurs in two forms, i.e. the α- and β-type, whereas β-hemihydrate is mainly applied since the hydration product of the α-hemihydrate is too …
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There is no steady state between hemihydrate dissolution and gypsum growth even in the first stages of the hydration process. The growth rate laws are either quadratic or linear according to...
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The TG used in this study was obtained from the LB Group (Jiao Zuo City, China) and dried at 50 ± 5 °C for 36 h. The chemical composition and X-ray diffraction (XRD) pattern of TG is shown in Table 1 and Fig. 1 (a), which indicate that the main component of the TG was CaSO 4 ·2H 2 O, with a fraction of 70–80 %. Up to 30 % of …
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Median hemidihydrate process requirements are given in Table 2. Dihydrate-Hemihydrate Process (DHH) Although the attack and digestion sections are run under dihydrate conditions, it is not desirable to effect a very high degree of P 2 O 5 recovery during the separation of the acid from the dihydrate because the succeeding …
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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 was also studied by Monte Carlo (MC) simulations. The thermodynamic calculation results reveal that the dehydration mechanism of gypsum …
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Because the typical average length of the gypsum crystals was 15 μm and thickness between 1 μm and 2 μm [30], the large particles were undoubtedly corresponding to hemihydrate particles, and the small particles were a mixture of hemihydrate and gypsum. Considering the hydration degree, it was easy to conclude that small particles …
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Learn how gypsum, hemihydrate and anhydrite react with water and change their crystal structure and solubility. See thermal analysis, dilatometry and solubility diagrams of gypsum and its phases.
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According to the data obtained for β-hemihydrate binder with SP and lime has low deformations started with low shrinkage in the initial time up to 0.04 mm/m with subsequent expansion up to 0.17 ...
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There are two significant differences between the gypsum structure and the prepared HH-CSW structure: one difference is that there are two H 2 O channels in the gypsum structure ... cost-effective transformation of FGD gypsum to calcium sulfate hemihydrate whiskers. Particuology, 54 (2021), pp. 173-180.
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Gypsum is a mineral (calcium sulfate dihydrate) used in construction; Plaster of Paris is a quick-setting gypsum product used in mold making and casting. Key Differences Gypsum, naturally occurring as a mineral, is widely used in the construction industry for drywall and plaster products.
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Understanding the differences between gypsum board and drywall is critical for making sound decisions in construction and restoration projects. Gypcore, the best Drywall suppliers in the Middle East, South Asia, and Africa offers a range of high-quality products designed to meet the region's construction demands."
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The water demand to convert them to the dihydrate form also differs (Powell & Way, 1962 ). α-Hemihydrate is difficult and expensive to generate and is employed to generate high-strength gypsum plasters, premium products used where strength is of prime importance: for instance for sanitaryware casing, block mould manufacture, architectural ...
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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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Chapter 12 Gypsum materials DEFINITION. Gypsum (calcium sulphate dihydrate) is a naturally occurring mineral used in dentistry to fabricate models (Figure 12.1a), casts and dies (Figure …
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Learn about the types, properties and uses of gypsum products in dentistry, such as plaster, dental stone and die. Gypsum is …
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Differences between hemihydrate crystals determine the characteristics and water to powder rations for each type of gypsum product. Model Pralster also reffered to as plaster of Paris is white and used primarlily for pouring up preliminary impressions to make diagnostic models for case presentations or in the use of orthodontics .
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The results indicates that H3PO4 accelerated hemihydrate gypsum dissolution and dihydrate gypsum precipitation, which included route I, involving Ca²⁺ and SO4²⁻, and route II, involving ...
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Using FGD gypsum as the raw material, whitening and large prismatic dihydrate gypsum can be obtained by dissolution-crystallization and decoloring process with α-hemihydrate gypsum whiskers prepared in MgSO 4-CaCl 2-H 2 O solution, which can transform into whitening short columnar α-hemihydrate gypsum. The effects of …
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