gypsum hemihydrate monohydrate gypsum and dihydrate gypsum in Oman
Gypsum hydration: a theoretical and experimental study
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 the nucleation and precipitation of dihydrate in the second stage. 2. Gypsum hydration is strongly influenced by water amount. Spread flow test is
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Structures of a) gypsum, b) hemihydrate, and c) …
The most prevalent sulfate mineral in the surrounding natural environment is calcium sulfate, which can be found as calcium sulfate dihydrate or gypsum (CaSO 4 ⋅2H 2 O), hemihydrate (CaSO 4 ⋅ ...
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Calcium sulfate hemihydrate-mediated crystallization of gypsum …
Spin-coated cellulose thin films have been used as model substrates to investigate the crystallization of calcium sulfate dihydrate (gypsum) under industrially relevant conditions using highly concentrated dispersions of calcium sulfate hemihydrate (bassanite).Pre-treatment of the films by regeneration in aqueous solutions of Ca 2+ promotes gypsum …
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The dihydrate‐hemihydrate transformation in gypsum
This dehydration step results in a negative solid volume change because of the decreasing molar volume of the denser product mineral: 74.53 cm 3 /mol for …
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Anion water in gypsum (CaSO4·2H2O) and hemihydrate …
The band 3600 cm −1 in hemihydrate is lowered to 3540 cm −1 in gypsum, and the band 3550 cm −1 in hemihydrate to 3400 cm −1 indicates the hydrogen bonding. Hemihydrate contains only one type of water molecule attached to the anion, SO 4 2−, by hydrogen bonding but gypsum contains two types of water molecules out of which one …
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Preparation of Whitening Dihydrate Gypsum and Short …
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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USG Gypsum Misconceptions White Paper (English)
Ground gypsum in and by itself will not get hard when mixed with water. Gypsum has to be converted to a "hemihydrate" by first cooking it. The process of cooking gypsum is called "calcination." As previously mentioned, two molecules of water are part of the gypsum (dihydrate) crystal.
ادامه مطلبSynthesis and Characterisation of Hemihydrate Gypsum…
This study combined inorganic α-hemihydrate gypsum (α-HHG) with organic polyacrylamide (PAM) hydrogel to create a novel α-HHG/PAM composite material. Through this facile composite strategy, this fabricated material exhibited a significantly longer initial setting time and higher mechanical strength compared to α-HHG. The …
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Preparation of α-High Strength Gypsum from Flue Gas …
The synthesis of α-calcium sulfate hemihydrate (α-CSH) from flue gas desulfurization (FGD) gypsum is a good way to realize the comprehensive utilization of FGD gypsum. To obtain α-CSH with the satisfactory performances, a facile hydrothermal-aging pretreatment process for FGD gypsum raw materials was proposed, where FGD …
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Recycling of waste gypsum from αlpha-hemihydrate …
1. Introduction. Phosphogypsum (PG) is the main solid waste in the phosphorus chemical industry. In the wet process production of phosphoric acid, which is a mainstream process of the phosphorus chemical industry, 4.5–5.5 tons of PG is emitted for each ton of P 2 O 5 production [1], [2], [3].The PG is mainly composed of dihydrate …
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Gypsum hemihydrate–cement blends to improve …
The microstructure of β-HH-BFSC blends are more compact and a C–S–H film covers the gypsum dihydrate needles, protecting them against water attack. ... From these initial findings, the question "gypsum hemihydrate–cement blends: are they possible?" can be answered. For the conditions employed in this work and using …
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Understanding gypsum in 3 diagrams
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 as, above 100°C, hemihydrate becomes less soluble than dihydrate. The solubility of …
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USG Gypsum Misconceptions White Paper (English)
By definition, gypsum is a "mineral of crystalline structure composed of calcium (Ca), sulfate (SO4) combined with two molecules of water.". The chemical equation is: …
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Dehydration Pathways of Gypsum and the Rehydration …
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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Gypsum: an investigation of microstructure and …
Gypsum (CaSO 4 ·2H 2 O, also as dihydrate) plaster is one of the earliest building materials elaborated by mankind, and gypsum plasterboard is used widely because of …
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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. ... 21 52 100 1,3 0,5 0,4 DH natural crystal before storage in furnace point 2 28 21 51 100 1,3 0,6 0,4 DH ...
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Aspects of gypsum dihydrate crystallization in the artificial …
The present paper investigates aspects of the crystallization of gypsum dihydrate during the artificial "aging" of calcined gypsum binder. ... in producing gypsum binders has received a great deal of attention in recent years owing to the instability of calcined gypsum properties [1]. Gypsum hemihydrate is a material used in the building ...
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Crystallization of gypsum from hemihydrate in presence of …
The crystallization of gypsum (CaSO 4 ·2H 2 O) from a suspension of calcium sulphate hemihydrate is well-known as the setting of plaster. In this paper we present results concerning the crystallization of gypsum in the presence of different acids. ... The three different stages, observed in Fig. 1, correspond to the hemihydrate …
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High-quality gypsum binders based on synthetic calcium …
A XRD pattern of β-calcium sulfate hemihydrate (Fig. 1, a), a SEM image (Fig. 1, b), and the dependence of the strength of gypsum on the temperature of its dehydration (Fig. 1, c) are shown in Fig. 1.The XRD pattern of β-calcium sulfate hemihydrate is fully assigned by the XRD pattern of hemihydrate as reported in …
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The Influences of Soluble Phosphorus on …
Phospho-gypsum is an industrial solid waste discharged from the phosphate production process. The waste includes complex impurities such as phosphoric acid and its salts, fluoride, and organics. Usually, …
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Structural characteristic and formation mechanism of …
Therefore, the mechanism of the HH-CSW formation from gypsum should be such that the two Ca–O–H bonds broken in the gypsum structure release H 2 O and …
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Preparation of hemihydrate gypsum with controllable …
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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Preparation of Whitening Dihydrate Gypsum and Short …
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 MgSO4‐CaCl2‐H2O solution, which can transform into whitening short columnar α‐hemihydrate gypsum. The effects of aging …
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Microstructure and mechanical properties of β-hemihydrate …
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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Calcium Sulfate Hemihydrate Whiskers Obtained from Flue …
Abstract: As a recycled material, flue gas desulfurization gypsum has been used to prepare calcium sulfate hemihydrate whisker (CSHW) through hydrothermal synthesis for several decades. However, the subsequent utilization of this resultant material has not yet received considerable attention. In the present research, CSHW was successfully synthesized at …
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Autoclave‐Free Formation of α‐Hemihydrate Gypsum
On comparing the solubility of calcium sulfate dihydrate and α-calcium sulfate hemihydrate in the formamide aqueous solution, it was found that the solubility of α-calcium sulfate hemihydrate is ...
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Fast in-situ X-ray scattering reveals stress sensitivity of …
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 …
ادامه مطلبWhat 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 main difference between calcium sulfate dihydrate and hemihydrate is their water content. Calcium sulfate dihydrate …
ادامه مطلبA new precipitation pathway for calcium sulfate dihydrate (gypsum…
This work investigates the early stages of precipitation of calcium sulfate from aqueous solution at room temperature and shows for the first time that amorphous calcium sulfate (ACS) and calcium sulfate hemihydrate are sequentially precipitated prior to calcium sulfate dihydrate (gypsum).
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Calcium sulphate hemihydrate hydration leading to gypsum
This article focuses on the hydration, and associated microstructure development, of β-hemihydrate to dihydrate (gypsum). The sound velocity is used to quantify the composition of the fresh slurry as … Expand. 5. PDF. Save. Preparation of α-Calcium Sulfate Hemihydrate from Phosphogypsum in CaCl2 Solution under …
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