Dehydration of gypsum waste to recyclable …
Here, we report the first solid-like dehydration of gypsum to produce anhydrite at room temperature. Specifically, a 39 nm thick sulfuric acid film (NSF) was fabricated to extract water of crystallization from …
Gypsum board dehydration kinetics at autogenous water …
Gypsum board dehydration. Gypsum board dehydration takes place at the temperature range between ∼80 °C and 250 °C, depending on the heating rate and the composition of the gypsum board [1], [10], [16], [17]. During this process the chemically bound water dissociates from the crystal mesh and, together with the free moisture …
Kinetics of Gypsum Dehydration at Reduced Rressure: An …
Gypsum (CaSO(4)center dot 2H(2)O) dehydration kinetics were investigated through energy dispersive X-ray diffraction (EDXD), under reduced pressure (100 Pa), in the temperature range 313-353 K.
Gypsum board dehydration kinetics at autogenous water …
DOI: 10.1016/J.TCA.2012.07.009 Corpus ID: 96999123; Gypsum board dehydration kinetics at autogenous water vapour partial pressure @article{Kontogeorgos2012GypsumBD, title={Gypsum board dehydration kinetics at autogenous water vapour partial pressure}, author={Dimos A. Kontogeorgos and Maria …
A 4D view on the evolution of metamorphic dehydration reactions …
Gypsum dehydration has proven to be analogous to reactions involving silicate minerals 18 but is much more suitable for synchrotron study since it completes in hours rather than years and begins ...
Gypsum hydration: a theoretical and experimental study
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 …
Structural evolution during the dehydration of gypsum …
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 by full structural 'Rietveld' refinement. In the study of the pure gypsum system, the hemihydrate structure is shown to be preserved as water is lost. ...
Understanding gypsum in 3 diagrams
The dehydration of gypsum can be observed using thermo-gravimetric measurement and differential scanning calorimetry. Depending on the parameters of measurement, a two-step process can be observed. The formation of beta-hemihydrate starts at around 85°C and is shifted into the formation of anhydrite III. Due to this, it is …
Insights Into the Micromechanics of …
Because gypsum contains water in its structure, it can accommodate large shear deformation under external load. Laboratory experiments show that during gypsum dehydration, the escaping water …
Effect of high temperatures on gypsum-based composites
Section snippets Thermo-chemistry of used materials. Calcined gypsum (commonly known as a Plaster of Paris) in powder form consists mainly of calcium sulphate hemihydrate CaSO 4 ·1/2H 2 O, which is prepared by dehydration of calcium sulphate dihydrate CaSO 4 ·2H 2 O (natural gypsum rock or an industrial by-product, e.g. from …
Insights Into the Micromechanics of …
Because gypsum contains water in its structure, it can accommodate large shear deformation under external load. Laboratory experiments show that during gypsum dehydration, the escaping …
Dehydration Pathways of Gypsum and the …
Gypsum is one of the most important minerals on earth, and its dehydration product, plaster of paris, is mainly used as a building …
Kinetics of gypsum dehydration at reduced pressure: an …
Gypsum dehydration experiments were carried out in the temperature range 313–353 K. In a typical run the pellet was inserted into the environmental chamber that was subsequently closed and evacuated. At this point the heating cycle was started under X-ray monitoring. As temperature reached the set value, counting time (1) where Iobs is the ...
Structural evolution during the dehydration of gypsum …
Abstract The dehydration of pure and waste gypsums has been examined using in situ synchrotron angle-dispersive X-ray diffraction. Pure gypsum was studied under a number of defined environments; various industrial waste gypsums were also studied under a common standard environment. It is found that the dehydration of …
Study of Gypsum Dehydration by Controlled
Abstract The dehydration of gypsum (CaSO4·2H2O) into calcium sulfate hemihydrate (CaSO4·0.5H2O) and anhydrites (γ-CaSO4andβ-CaSO4) was carried out by heating under a constant pressure of water vapor using Controlled transformation Rate Thermal Analysis. No intermediate formation of calcium sulfate hemihydrate occurred …
In situ IR spectroscopic and thermogravimetric study of the dehydration …
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 …
Experimental VNIR reflectance spectroscopy of gypsum …
The spectral behavior of gypsum dehydration in the visible to near-infrared (350–2500 nm) wavelength range was investigated by partially dehydrating the four …
Ingenious approach for retrieving valuable metals from gypsum …
Under natural conditions, dehydration from gypsum to the hemihydrate/anhydrate phases is slow; hence, low energy is introduced to accelerate this process. Metal-incorporated gypsum was calcined in a muffle furnace at 200–400°C for 2 h and transferred into a desiccator after cooling to approximately 100°C.
Dehydration of Gypsum Rock by Solar Energy: Preliminary …
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.
Structural evolution during the dehydration of …
Such a diversity of results helps to explain why there is so much confusion in the literature concerning the gypsum-dehydration-transformation scheme. A more definitive view can be obtained by establishing a …
The dehydration process of gypsum under high pressure
The effects of pressure on the dehydration of gypsum materials were investigated up to 633 K and 25 GPa by using Raman spectroscopy and synchrotron X-ray diffraction with an externally heated diamond anvil cell. At 2.5 GPa, gypsum starts to dehydrate around 428 K, by forming bassanite, CaSO4 hemihydrate, which completely …
Predicting Depths of Gypsum Dehydration in Evaporitic …
The conversion of gypsum to anhydrite upon burial and heating is accompanied by about a 39% volume decrease, a four-fold increase in thermal conductivity, and consumption of heat. Accurate "back-stripping" of an evaporite basin and tracking its thermal evolution requires a knowledge of the depth of the gypsum-anhydrite transition. …
The Simulation and Analysis of Dehydration Process of FGD Gypsum …
The Simulation and Analysis of Dehydration Process of FGD Gypsum Grouted Wall: ZENG Ziyue 1,2, YANG Jiansen 1, WEI Yongqi 2: 1 School of Civil and Hydraulic Engineering, Ningxia University, Yinchuan 750021, Ningxia, China 2 School of Material Science and Engineering, Tongji University, Shanghai 201804, China
Dehydration Pathways of Gypsum and the Rehydration Mechanism …
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 …
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. …
Physicomechanical Properties of Gypsum with Mineral …
There was tremendous pore water loss, and gypsum dehydration happened at 100 °C and 200 °C, leading to a porous structure that weakened the strength of the gypsum matrix. After the 300 °C treatment, the dehydration of gypsum was likely completed, forming a more robust anhydrate phase that increased the strength of the …
Tectonic Implications of Gypsum Dehydration | GSA …
The effect of dehydration on the strength of gypsum was chosen for investigation partly because of the known occurrence of evaporites along many thrust faults but chiefly because this dehydration was considered to be typical of, but more tractable o t laboratory investigation than, the hydrous-anhydrous reactions of many metamorphic rocks. ...
Experimental VNIR reflectance spectroscopy of gypsum dehydration
Abstract The spectral behavior of gypsum dehydration in the visible to near-infrared (350-2500 nm) wavelength range was investigated by partially dehydrating the four main habits of gypsum (alabaster, satin spar, selenite, and massive) to form bassanite. Powdered samples of gypsum dehydrated at 100-115 °C and hand samples dehydrated …
Thermal behaviour and kinetics of dehydration of gypsum …
The thermally induced dehydration processes of gypsum, and the corresponding empirical activation energies E a, have been extensively studied in the past, as a function of both temperature and ( P_{{{text{H}}_{ 2} {text{O}}}}, ) using different experimental techniques. As gypsum dehydration has great technological relevance, …
Kinetics of gypsum dehydration
A systematic study was conducted to investigate the correlation between the dehydration of gypsum and the time and temperature of calcination as well as the grain size of the starting material.It was found that the proposed formula may be considered as a real expression of the dehydration raction throughtout the major part of α. However, the …