The development of a multimillion-dollar gypsum industry was made possible by the following factors: (1) Gypsum is an abundant, naturally pure raw material. (2) It can be dehydrated to the hemihydrate at relatively low …
→ WhatsApp: +86 18221755073
Gypsum (calcium sulfate dihydrate, Fluka, 99.9% purity) samples were dehydrated at temperatures from 85 up to 800 °C 25 g of substance was weighed in corundum crucibles of 60 ml size and dehydrated in two different furnace types to cover the complete temperature range.The furnaces were calibrated with thermo elements.
→ WhatsApp: +86 18221755073
The obtained dehydrated gypsum contained combined gypsum phases of dihydrate, hemihydrate, and II-anhydrite. Cao et al. [23] also found that the soluble phosphate content decreased after calcination at 500 °C. All the experimental results of previous researches have illustrated that the content of soluble phosphates in the dehydrated PG ...
→ WhatsApp: +86 18221755073
It is found that the dehydration of gypsum to anhydrite proceeds via the hemihydrate and γ-anhydrite phases and the interplay and behaviour of these phases has been determined …
→ WhatsApp: +86 18221755073
Here, we perform fast, time-resolved synchrotron X-ray scattering on natural alabaster samples, finding that a small elastic load accelerates the dehydration reaction …
→ WhatsApp: +86 18221755073
Alpha-hemihydrate gypsum B a Alpha-hemihydrate gypsum a a a a a a b Dihydrate gypsum b b b c Calcium hydroxide d Calcium carbonate e Hemihydrate calcium sulfite c c c d e d d e e Fig. 1. Particle size distributions and XRD patterns of hemihydrate gypsum and desulfurized ash. H. Li, et al. Fuel 255 (2019) 115783 2
→ WhatsApp: +86 18221755073
Nesquehonite (NQ) can be activated via thermal treatment under 50–175°C, after which the dehydrated nesquehonite can hydrate to form a plaster-like product, like gypsum-based plaster. Here, we developed different blends of NQ and hemihydrate (dehydrated gypsum) to produce plaster.
→ WhatsApp: +86 18221755073
Phosphogypsum (PG) is a kind of industrial solid waste with high impurity content and low utilization rate. In this study, α-hemihydrate gypsum (α-HH) was synthesized from PG in H 3 PO 4 –H 2 O solution (wet-process phosphoric acid solution and phosphoric acid solution) under atmospheric pressure. The crystal morphology of α-HH was controlled by adding F and …
→ WhatsApp: +86 18221755073
A 'zero-water hemihydrate' is observed before refinement in the higher symmetry γ-anhydrite cell is possible. The waste gypsum materials studied showed significant differences in the temperatures at which key transformation events occurred; these observations raise implications concerning the re-use of by-product gypsum materials.
→ WhatsApp: +86 18221755073
Plaster, made of calcium sulfate hemihydrate (CaSO 4 •½H 2 O) and/or γ -anhydrite (CaSO 4) is obtained by dehydration of gypsum (CaSO 4 ·2H 2 O) at 100–200 °C. When …
→ WhatsApp: +86 18221755073
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 the hemihydrate. This process was historically centred in Paris, where large gypsum deposits were found and widely used for making quick-setting materials.
→ WhatsApp: +86 18221755073
Gypsum-based binders are generally based on the reaction between calcium sulfate hemihydrate (HH) and water to form calcium sulfate dihydrate (DH). Often gypsum can be used as a raw material to obtain hemihydrate. In this study, the obtained alpha hemihydrate consists of large crystals that have more or less lattice defects according to its ...
→ WhatsApp: +86 18221755073
This work firstly shows that the observed crystallization inside of gypsum during dehydration is the formation of alpha-hemihydrate. Gypsum (calcium sulfate dihydrate) is one of the most used inorganic binding materials …
→ WhatsApp: +86 18221755073
A high hemihydrate content results in false setting of the cement, thus a maximum percentage of the hemihydrate is required in gypsum samples [3]. It is shown in the literature that the decomposition of calcium sulphate dihydrate proceeds via two reactions [4, 5] CaS04- 2H20 (s) -. CaS04 -0.5H20 (s) + 1.5Hz0 (g) CaS04 -0.5H20 (s) ~ CaS04 (s ...
→ WhatsApp: +86 18221755073
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. Especially because of the ...
→ WhatsApp: +86 18221755073
This work firstly shows that the observed crystallization inside of gypsum during dehydration is the formation of alpha-hemihydrate.
→ WhatsApp: +86 18221755073
Gypsum crystal partly dehydrated, cleaved along cleavage plane, with observable dihydrate, α β α-hemihydrate and β-hemihydrate. Yellow circle = still dihydrate, blue circle = alpha hemihydrate, red circle = beta hemihydrate, black arrow = alpha hemihydrate growing direction of …
→ WhatsApp: +86 18221755073
Gypsum raw material (reagent gypsum, phosphogypsum and processed phosphogypsum) was dehydrated by dry method (i.e. in dry air environmental) and wet method (i.e. saturated water vapour...
→ WhatsApp: +86 18221755073
The dehydration products of gypsum under different temperature and water vapor pressure were investigated by thermodynamic theory. Additionally, the rehydration mechanism of soluble anhydrite...
→ WhatsApp: +86 18221755073
Factors affecting these results include the type of added gypsum (for example when hemihydrate calcium sulfate, i.e. bassanite, is used instead of gypsum, or when solid waste byproducts such as titanium gypsum, phosphorous gypsum, and desulfurization gypsum are used instead of pure gypsum), the type and percentage of fine portion of the soil ...
→ WhatsApp: +86 18221755073
The temperature at which the gypsum binder (calcium sulfate hemihydrate) is industrially produced, between 80 and 180 °C, is often mentioned in the literature [14,15,16,17].However, dehydration from gypsum to basanite (CaSO 4 ·0.5H 2 O) starts at a much lower temperature. The dehydration temperature depends on the measurement method, the …
→ WhatsApp: +86 18221755073
The dehydration of gypsum to hemihydrate has been studied for decades because it is an important model reaction for understanding fluid-triggered earthquakes, and due to the global use of plaster ...
→ WhatsApp: +86 18221755073
The gypsum powder was stored for 24 h in a 100 °C oven, where mainly it dehydrated into hemihydrate, next to small amounts of anhydrite. ... The calculated saturation indices from porewater data of both gypsum and hemihydrate are reflecting one another in each sample and follow the sulfur concentrations (Fig. 6). The saturation of hemihydrate ...
→ WhatsApp: +86 18221755073
dehydration still needs further investigation, especially the behaviour of the β-hemihydrate and gypsum produced from it is still poorly understood. This article focuses on the role of water on the properties of gypsum produced from a β-hemihydrate due to its combined effect on both hydration and dehydration.
→ WhatsApp: +86 18221755073
The industrial application of PG is mainly focused on building gypsum (β-CaSO 4 ·0.5H 2 O) [5], α-hemihydrate gypsum (α-CaSO 4 ·0.5H 2 O, α-HH) [6], [7], cement retarder [8], sulfuric acid co-production cement [9], soil conditioner [10] and so on. Among which, the preparation of α-HH using PG is one of the most profitable approaches because α-HH is a …
→ WhatsApp: +86 18221755073
Only gypsum dehydrated in a vacuum or in a very low water pressure is likely to rehydrate. The mechanism "Le Chatelier" would not be only one to apply during hydration with liquid water. ... The dehydration conditions of calcium sulphate dihydrate can strongly modify the rehydration mechanism of the hemihydrate. Only gypsum dehydrated in a ...
→ WhatsApp: +86 18221755073
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 in two …
→ WhatsApp: +86 18221755073
Dehydrated phases (Hemihydrate and γ-Anhydrite) are formed as exfoliated pseudomorphic flakes through topotactic transformation along [010] and show two sets of oppositely dipping slip systems. During the late dehydration stage (120–140°C), plastic strain is accommodated by the sliding of these flakes along with inelastic pore compaction ...
→ WhatsApp: +86 18221755073
Abriel et al. studied the dehydration mechanism of gypsum using neutron and X-ray diffraction (XRD) and proposed a novel gypsum …
→ WhatsApp: +86 18221755073
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 dehy …
→ WhatsApp: +86 18221755073
Stone Crusher-sold by certified Suppliers,such as Jaw / Cone / Impact / Mobile Crusher,etc.
GET QUOTE
