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When gypsum (CaSO4·2H2O) is exposed to water, it undergoes partial dehydration, leading to the formation of beta hemihydrate as an intermediate product. This …
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Normally, calcium sulphate dihydrate (CaSO 4 •2H 2 O) is used as a raw material and a subhydrate such as hemihydrate (CaSO 4 •0.5H 2 O) or anhydrite (CaSO 4) is …
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The formation process of hemihydrate in gypsum primarily involves the dehydration of calcium sulfate dihydrate (CaSO₄·2H₂O) through heating. This process can be observed in two main …
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The α-hemihydrate form of gypsum is generally the binder for investments used in casting gold-containing alloys with melting ranges below 1000 °C. When this material is heated at temperatures sufficiently high to …
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Gypsum Products commercially available are hemihydrate form of calcium sulfate. Gypsum products used in Dentistry are broadly classified into 5 types Type 1- Impression …
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This article addresses the microstructure and related mechanical properties of gypsum produced from β-hemihydrate using information of its hydration process, from fresh …
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Thus, gypsum plaster should be applied to a thickness of 6-20 mm. For the undercoat, the thickness of gypsum plaster is: For walls = 11 mm, For ceilings = 8mm. ...
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The hydration properties of hemihydrate gypsum and anhydrite affect the quality of MPPG-based materials. Anhydrite has a much slower hydration rate and strength …
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When the proportion of α-type hemihydrate gypsum in the calcined plaster increases, the standard water mixing ratio decreases. 03. For the same calcined plaster, reducing the water-to-plaster …
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Results indicate that when the hemihydrate gypsum content ranges from 15 % to 30 %, the trend of gel pores remains stable between 27 % and 31 %. As the amount of …
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CAH 10 and C 2 AH 8 are the main hydration products in CAC and they are responsible for its high strength at the early age [9].However, they are metastable and easily …
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The Central-Prayon Process (CPP) is used to one of Prayon's production site and has been in operation for more than 40 years. This is a model of the circular economy in the phosphoric …
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consumption of hemihydrate and formation of dihydrate. 1. Ultrasonic results indicate gypsum hydration reaction consists of two stages: the dissolution of hemihydrate in the first stage and …
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Gypsum modification is an effective strategy to improve the water resistance of magnesium oxychloride cement paste (MOCP), but its early-ages performance evolution has …
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When Gypsum (CaSO4,2H2O) is ground to a powder and heated at 150° to 165° C, three-quarters of its combined water is removed producing hemi-hydrate plaster (CaSO4,1/2H2O), …
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Alpha-hemihydrate gypsum (α-HH), also referred to as alpha-type high-strength gypsum, is a critical cementitious material distinguished by its low length-to-diameter (L/D) …
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a Plaster of paris is calcium sulphate hemihydrate. Its chemical formula is: CaSO .1/2H O.b It is prepared by heating gypsum to a temperature of 100 C in a kiln; it loses 3/4th of its water of …
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where r ij and σ ij are the actual and reference distances between atoms i and j, respectively; ε o is the permittivity of free space (ε o = 8.8543 × 10 –12 C 2 J –1 m –1); ε ij is the potential well …
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Calcium Sulphate Hemihydrate is called Plaster of Paris because it is derived by heating gypsum (calcium sulfate dihydrate) to around 150°C, which removes water and forms …
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When water is added to either hemihydrate or anhydrite, these phases rehydrate to form gypsum in an exothermic reaction. Two phases of hemihydrate result when gypsum is …
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Gypsum products such as dental plaster and stone are important materials used in prosthodontics. Dental plaster (Type I and II) sets to a softer material used for impressions and …
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Gypsum only requires water for hydration until it has set (gets hard), therefore the cross- sectional thickness is not susceptible to differential shrink. Calcium sulfate hemihydrate, as described …
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The specific surface areas of α-hemihydrate gypsum (HG), anhydrite (SG), dihydrate gypsum (DG) were 364 m 2 /kg, 639 m 2 /kg, and 521 m 2 /kg, respectively; the chemical compositions …
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Hydration behavior []. The system CaSO 4 –H 2 O: Calcium sulfate can appear in three different hydrate phases: Anhydrite (CaSO 4)- the above mentioned anhydrous form.; Bassanite (hemihydrate) (CaSO 4 •0.5H 2 O)- a metastable …
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Beta hemihydrate gypsum is suitable for construction applications where early high-strength development is necessary. Because alpha hemihydrate makes a denser, higher-strength cast, …
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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 …
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Whereas control specimens based on hemihydrate binder has higher level of shrinkage (up to 0.08 mm/m) with subsequent achieving expansion up to 0.03 mm/m at the …
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There are two basic forms of gypsum hemihydrate used in dentistry: α-Hemihydrate (Type III, IV, and V gypsum): Formed under pressure with steam, it has denser, more uniform crystals and …
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The order of succession is as follows: gypsum, hemihydrate, "soluble anhydrite", and anhydrite. The reactions that alter gypsum to the other calcium sulfate minerals are …
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However, the rapid hydration of β-HH limits its operational time, significantly restricting its market application. Typically, the initial setting time for gypsum is only 5–10 min; …
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