gypsum dehydration individual

(PDF) Dissolution and conversions of gypsum and anhydrite

The changes from gypsum to anhydrite and back to gypsum are common processes (Klimchouk, 2000). This way, James (1992) noted that in very hot climates gypsum can dehydrate to anhydrite when it is ...

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Statistical approaches in the analysis of in situ thermo ...

The dependence of the intermediate products of gypsum dehydration on the measurement conditions and the state of sample was confirmed. A detailed analysis of the temperature behavior of ν 1 (SO 4 ) in a single crystal indicated the coexistence of CaSO 4 ·2H 2 O + γCaSO 4 (380–440 K) and γ-CaSO 4 + β-CaSO 4 (680–740 K) phases, which was ...

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In situ micro-Raman investigation of dehydration mechanism ...

that the dehydration phenomenon is more temperature dependent than pressure-dependent',4,6,7. In fact, the tran sition temperature of gypsum to bassanite linearly shifts upwards with pressure8. The transition sequence and the individual phases were earlier studied by many techniques, including IR and Raman spectroscopic methods'9'2.

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gypsum dehydration - German translation – Linguee

Certain workplace types, e.g. the "Stucco plasterers / plasterers" and "Crane drivers in the manufacture of products from concrete, cement and gypsum" and also "Screed and terrazzo layers in the working and processing of natural stone" also have very high sickness rates, but comparatively few insured persons are employed in these areas, and so individual cases with long-drawn-out illnesses may ...

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Heat and Mass Transfer in a Gypsum Board Subjected to Fire

dehydration of gypsum at elevated temperatures. Dehydration is an endothermic chemical reaction, which consumes energy and thus acts as a heat barrier. The effect of dehydration can be introduced in a heat conduction model by a ... The individual heat capacities in J/(kg·K)

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Reaction fronts, permeability and fluid pressure ...

Gypsum alabaster has a very low starting porosity and permeability meaning that fluid can be efficiently overpressured at the onset of dehydration. If the fluid pressure during reaction exceeds the confining pressure sufficiently, hydrofracturing may occur and fractures could form preferential fluid pathways ( Zhu et al., 2016 ).

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Experimental VNIR reflectance spectroscopy of gypsum ...

Gypsum dehydration experiment Four gypsum samples constituting the main polycrystalline habits of gypsum (alabaster, massive, satin spar, and selenite) were obtained from Ward's Natural Science and dehydrated to examine changes in the reflectance spectrum over the 350–2500 nm wavelength region and to determine if habit has any effect on the

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Thermal Analysis of Gypsum - High-Tech

NOV.1985 Thermal Analysis of Gypsum 1. Introduction Gypsum has long been used as a building material and is used for that purpose in the following items. • Setting retarder for Portland cement • For gypsum plaster, gypsum board, ceramic molding tools, and arts and crafts • Auxiliary material for nickel smelting and a source of sulfur

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A 4D view on the evolution of metamorphic dehydration ...

Like most dehydration reactions, the breakdown of gypsum involves a reduction in the solid molar volume, which leads to the formation of porosity (29% when fully dehydrated).

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Apparatus for the thermal conversion of gypsum - Rhone ...

Apparatus for the progressive thermal dehydration of gypsum into a calcium sulfate hemihydrate having enhanced mechanical properties and reactivity, said apparatus comprising (i) a dehydration zone including an inlet end, an outlet end, and a plurality of distinct communicating compartments there-between, each compartment defining an individual ...

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EJM - Sequential dehydration of the phosphate–sulfate ...

Individual crystals are platy on (0001) and typically smaller than 10 ... of the gypsum–bassanite equilibrium was largely observed in order to explain the topotactic transformation of gypsum into bassanite by natural dehydration, especially in arid environments such as the Sahara Desert (e.g., Mees and Stops, 2003, and references therein). ...

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Gypsum board dehydration kinetics at autogenous water ...

The estimation of apparent activation energy for each individual step of the thermal dehydration of gypsum sample was obtained using isoconversional Fr, KAS and FWO methods, as indicated by Eqs.

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Gypsum - an overview | ScienceDirect Topics

Gypsum is the name given to a mineral categorized as calcium sulfate mineral, and its chemical formula is calcium sulfate dihydrate, CaSO 4 ⋅ 2H 2 O. However, a broader definition includes all the calcium sulfates, including calcium sulfate hemihydrate, CaSO 4 ⋅ 0.5H 2 O, which is known as plaster or plaster of Paris (POP). Figure 6 summarizes the polymorphism of calcium sulfate; 'g ...

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Synchrotron X-ray experiment reveals a small nudge with ...

More information: Christoph Eckart Schrank et al, Fast in-situ X-ray scattering reveals stress sensitivity of gypsum dehydration kinetics, Communications Materials (2021). DOI: 10.1038/s43246-021 ...

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The crystallization water of gypsum rocks is a relevant ...

Gypsum (CaSO 4 ·2H 2 O) is a rock-forming mineral that also occurs in soil 1.Gypsum outcrops are widespread throughout the Earth, being present in the five continents 2.They are particularly ...

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1. GYPSIFEROUS SOILS IN THE WORLD - Home | Food and ...

Dehydration starts at 40°C and reaches a level corresponding to the semi-hydrate (bassanite) at 70-90°C. Above 100°C or even 200°C, the salt still contains about 0.01 mole of water per mole. Gypsum is formed in two ways: by crystallization from an aqueous solution, or by the hydration of anhydrite. It crystallizes as monoclinic prisms.

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KGS--Gypsum in Kansas--Geology

McCormak (1926) likewise concluded that temperature was a more important factor than pressure in the dehydration of gypsum. He added, however, that pressure plus time in the geologic sense is an unknown factor and may have more influence on the dehydration of gypsum than any laboratory experiments could indicate.

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DETERMINATION OF GYPSUM CONTENT – MSK

~ 110-200º C: wt/ loss due to gypsum crystal water ~ Dehydration of calcium hydroxide thereafter. As it is quite evident that the wt. loss in case of cement due to the presence of gypsum is very small, therefore a separate curve has been made using the alumina-gypsum composite containing 0-5 wt.% of gypsum in the composite.

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Novel approach to thermal degradation kinetics of gypsum ...

12%The estimation of apparent activation energy for each individual step of the thermal dehydration of gypsum sample was obtained using isoconversional Fr, KAS and FWO methods, as indicated by Eqs. ( 8 ), ( 10 ) and ( 12 ), in α interval …

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Fast in-situ X-ray scattering reveals stress sensitivity ...

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 …

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In situ IR spectroscopic and thermogravimetric study of ...

The dehydration of gypsum CaSO 4.2H 2 O has been studied, at negligible water vapour pressure, by in situ infrared (IR) spectroscopy and by thermogravimetry to determine whether intermediate phases (CaSO 4. n H 2 O) exist, other than the hemihydrate with n =0.5, and also to compare the mechanism of the dehydration process when measured by two techniques with very different correlation lengths.

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Moisture transport, condensation and dehydration of gypsum ...

Gypsum plasterboard acts as a protective barrier for the load bearing wood or steel frame it is attached to. As gypsum is a very clean and well defined material we have also used is as a benchmark material to study the processes like interpret moisture and/or dehydration at high temperatures.

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China Toncin FGD Gypsum Dehydration Rubber Belt Vacuum ...

China Toncin FGD Gypsum Dehydration Rubber Belt Vacuum Filter, find complete details about China Toncin FGD Gypsum Dehydration Rubber Belt Vacuum Filter, FGD VACUUM BELT DEHYDRATOR, Slurry Dewatering Plant, Power Plant - Nuclear Industry Yantai Toncin Group Co.,Ltd.

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Disentangling water sources in a gypsum plant community ...

Xylem water was distilled at 130 °C, whereas gypsum soils were distilled in two steps: first at 35 °C, and then at 130 °C to separate free and crystallization water and ensure almost complete dehydration of gypsum (Freyer and Voigt, 2003; Palacio et al., 2014b). Between the first and second distillation, sample tubes were kept in a ...

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The hydrophobic modification of gypsum binder by peat ...

the threshold for intensive dehydration of gypsum. In the second stage (B–С), the temperature is held at 120 °C for 30 minutes. This stage is characterised by intensive dehydration of the material with the removal of crystal water. In the third and final stage (С–D), duration 35–40 minutes, the temperature rises rapidly to 180 °C.

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RAPID, IMPACT-INDUCED DEHYDRATION, MELTING, AND ...

gypsum to 1017cm –1. in bassanite to 1018 cm –1. in anhydrite). In addition, dehydration of gypsum is also evident from back-scattered electron (BSE) images obtained from the irradiation zones by an increase in brightness and by the presence of cracks in individual bassanite and …

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Novel approach to thermal degradation kinetics of gypsum ...

The estimation of apparent activation energy for each individual step of the thermal dehydration of gypsum sample was obtained using isoconversional Fr, KAS and FWO methods, as indicated by Eqs. ( 8 ), ( 10 ) and ( 12 ), in α interval ranged between 0.2 and 0.8 with step of 0.05.

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US5169617A - Method of treating produced gypsum - Google ...

A method for treating produced gypsum and, in particular, a method for treating flue-gas desulfurization gypsum forms highly active, modifiable gypsum binders of high strength with simultaneously drying, deagglomerating and dehydrating. Pursuant to the invention, produced gypsum (flue-gas desulfurization gypsum), with a particle size ranging up to 200 μm, to which 10% by weight of milled ...

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Dehydration-induced damage and deformation in gypsum …

Gypsum undergoes brittle-ductile transition at moderate pressure (around 10 to 20 MPa confining pressure [Brantut et al., 2011]) and dehydration at less than 150 C, which is easily attainable is a triaxial apparatus using oil as a confining medium [e.g., Ko et al., 1997]. [5] In this paper we present a series of dehydration tests

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Permeability of gypsum samples dehydrated in air - Milsch ...

[3] Gypsum has repeatedly been used as an analog material principally for its abundance and its low dehydration temperature. Ballirano and Melis [2009] concluded that in air, at a water vapor partial pressure of ca. 1.4 kPa, and in the temperature range of 348 to 403 K, gypsum (CaSO 4 •2H 2 O) dehydrates to γ -anhydrite (CaSO 4 ) via an ...

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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 …

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Gypsum Plaster Market Swot Analysis by Key Players VANS ...

Gypsum plaster, white cementing material made by partial or complete dehydration of the mineral gypsum, commonly with special retarders or hardeners added. Gypsum Plaster Market Swot Analysis by Key Players VANS Gypsum, Shreenath Gyptech, Sherlock Industries - The Cowboy Channel

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Physical and Mechanical Properties of Gypsum-Like Rock ...

In the process of tunnel construction, gypsum rock is often encountered, and the volume of gypsum rock expands when encountering water, which is easy to cause the occurrence of rock fall, collapse, and other disasters, bringing serious challenges to the safe construction of the tunnel. Therefore, in this paper, four groups of samples under different moisture content are tested by ...

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