Gypsum in construction: origin and properties
The origin of gypsum, its genesis, varieties and properties are discussed, and the focus is then on the most common binding material produced from it, plaster of Paris (β-hemihydrate), …
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Calcium Sulfate Hemihydrate
Naturally occurring crystals are calcium sulfate dihydrate, CaSO 4 ·2H 2 O, known as gypsum, and anhydrous calcium sulfate, II-CaSO 4. When gypsum is heated, dehydration occurs to …
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Gypsum Soils—Their Morphology, Classification, Function, and Landscapes
Chemical names for the three hydration states of calcium sulfate are dihydrate, hemihydrate, and anhydrous or anhydrate, respectively. Gypsum is the most abundant sulfate mineral in soils and has been described in arid and semiarid soils around the world and recently in soils on Mars (NASA, 2011). Bassanite is very rare in nature as it is ...
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One-step synthesis of short columnar α-calcium sulfate hemihydrate …
The exothermic peak at 365.1 ℃ corresponded to the conversion of γ-CaSO 4 to insoluble anhydrous gypsum ... the difference in the adsorption sites of sodium citrate on α-HH crystal planes ...
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Hemihydrate
Sustainability of gypsum products as a construction material. N. Lushnikova, L. Dvorkin, in Sustainability of Construction Materials (Second Edition), 2016 β-Hemihydrate binder. β-Hemihydrate (also known as plaster of Paris) is the most commonly used gypsum binder in construction.It is produced in an apparatus connected to air. Different equipment is used, …
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Preparation of α-calcium sulfate hemihydrate from …
gypsum, flue gas desulfurization (FGD) gypsum and phosphogypsum (PG) have the largest output. FGD gypsum originates from the flue gas desulfurization installations by sorption of SO 2 in power stations. For example, in the wet-lime desulfurization method, the sorption reaction occurs via the reaction formulas (1, 2) (Roszczynialski et al., 1996a).
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Calcium Sulfate Dihydrate
The gypsum (hydrated) forms of these materials are then processed and heated under controlled conditions to form plaster of Paris, or calcium sulfate hemihydrate (CS, CaSO 4 · 1/2H 2 O). Addition of water to this material, in proper quantities, causes setting of the plaster of Paris to form calcium sulfate dihydrate (CaSO 4 · 2H 2 O).
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Gypsum Plaster: Types, Advantages & Disadvantages
Gypsum is heated to remove all its combined water resulting in the product known as anhydrous gypsum which is ground with an accelerator to make a hydrous gypsum plaster. ... It is manufactured by heating gypsum to 1700C. Hemihydrate gypsum plaster: It is produced when the gypsum is heated to more than 1700 C. Gypsum plasters based on the ...
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The Solubilities and Thermodynamic Equilibrium of …
The direction of a chemical reaction depends on the difference in the Gibbs Free Energy G between the products and the reactants: Any transformation in a system takes place …
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Innovative synthesis of high-strength α-hemihydrate gypsum…
High-strength gypsum is the recognized designation for α-hemihydrate gypsum, often referred to as α-HH (CaSO 4 ·0.5H 2 O), which is a cementitious material with low water requirement and high strength [8].The strength of α-HH is generally between 25 and 50 N/mm 2, which is three times that of ordinary building plaster, and has superior working performance. α …
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Preparation of Medium–Low Strength Hemihydrate Gypsum …
This study explored the production of a medium–low strength α-hemihydrate gypsum (α-HH) from phosphogypsum using an autoclaved method. The influence of slurry concentration, spreading thickness, crystallizing agents, slurry pH, autoclaving temperature, and autoclaving time on the properties of α-HH was investigated. The energy consumption of …
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Plaster of Paris
Gypsum is represented by the chemical formula CaSO 4.2H 2 O. Why is Calcium Sulphate Hemihydrate called Plaster of Paris? Calcium Sulphate Hemihydrate is called Plaster of Paris because of the fact that it is prepared from the chemical compound called gypsum which is found to be most abundant near Paris.
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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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Gypsum vs. Anhydrite: What's the Difference?
Gypsum, a widely used mineral, is known for its softness and is composed of calcium sulfate dihydrate. Anhydrite, on the other hand, is a hard mineral, the anhydrous form of calcium sulfate, and is often found in salt deposits.
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Gypsum | Common Minerals
In crystal form, its softness and single perfect cleavage with two less well-developed cleavage directions usually serve to distinguish gypsum from other similar-looking minerals. Anhydrite: When gypsum loses its water component, …
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The study on the effect of flotation purification on the performance …
The currently commonly used PG pretreatment methods can partially solve the impurity problem, such as using high-temperature calcination to obtain hemihydrate or anhydrous gypsum for use as cement ...
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2.12: Hydrates
Any anhydrous compound from a hydrate generally has the following properties: Highly soluble in water; When dissolved in water, the anhydrous compound will have a color similar to that of the original hydrate even if it had changed color going from the hydrate to the anhydrous compound. Most hydrates are stable at room temperature.
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Structures of a) gypsum, b) hemihydrate, and c) …
Wolfgang Voigt. 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...
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Preparation of high-performance building gypsum by calcining FGD gypsum
The first endothermic peak at 150 °C refers to the dehydration of CaSO 4 ·2H 2 O into hemihydrate gypsum. The FGD gypsum begins to dehydrate at about 110 °C and ends at about 190 °C, indicating that the crystal water is completely removed. ... (140 °C), and anhydrous gypsum does not appear at high temperature (220 °C), indicating that CaO ...
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Anhydrite and gypsum
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 and marginal marine environments …
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Gypsum | Properties, Formation, Uses and Deposits
Gypsum, a naturally occurring mineral with the chemical formula CaSO4·2H2O, exhibits several important chemical properties that contribute to its versatility and usefulness in various applications. Here are some key chemical properties of gypsum: 1. Hydrated Structure:Gypsum is a hydrated mineral, meaning it contain…
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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 …
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 dehydration …
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Calcium sulfate
Drierite (anhydrous) Gypsum Plaster of Paris. Properties Chemical formula. CaSO 4: Molar mass: 136.14 g/mol (anhydrous) 145.15 g/mol (hemihydrate) 172.172 g/mol (dihydrate) Appearance ... Calcium sulfate exists in three hydrates, a dihydrate, a hemihydrate and a anhydrous form. Over 100 degrees the hemihydrate is formed and it looses water to ...
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DM chapter 16: Gypsum & Wax Products Flashcards
Study with Quizlet and memorize flashcards containing terms like 1. Which of the following is true concerning the chemical properties of gypsum materials? a. Chemically, the mineral gypsum is a hemihydrate of calcium carbonate. b. To form the raw material into a powder, the manufacturer heats it and adds water. C. When the dihydrate is again mixed with water, a product with a …
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Experimental Study and Mechanism Analysis of …
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 …
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What is the Difference Between Alpha and Beta Hemihydrate
The difference between alpha and beta hemihydrate is their solubility. Alpha hemihydrate is more soluble and sets faster than the beta form. EXPLORE. Travel & Tour; Education; Language; ... The process of converting gypsum into alpha hemihydrate involves heating gypsum at a specific temperature to remove water molecules, resulting in a more ...
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The anhydrous calcium sulphate is called.
The anhydrous calcium sulphate is called Anhydrite. [CaS{O_4}] is anhydrous state or anhydrite. Thus option (B) is the correct answer. Note: If the heating is at a higher temperature, gypsum loses all its water and becomes anhydrous calcium sulfate, ([CaS{O_4}]). Calcium sulphate is majorly used in the manufacturing of plaster of paris.
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Dissolution and conversions of gypsum and …
The difference in solubility between gypsum and calcite decreases to 10-30 times if the latter is dissolved in the presence of CO2. The dependence of the solubility of gypsum on temperature is ...
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Gypsum: an investigation of microstructure and …
The hydration and dehydration of gypsum has been investigated intensively so far, whereas the emphasis is mainly on α-hemihydrate.
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