In the low-temperature and high water vapor zone above curve AB in Figure 2, gypsum is thermodynamically stable; in the ABC zone, CaSO 4 ·2H 2 O will partially dehydrate its crystal water to form β-CaSO 4 ·0.5H 2 O, and as the …
The dehydration processes and the chemical reactions character-ize the temperature-depended thermal properties of gypsum plasterboards. 2.2 | Thermal properties of gypsum plasterboards—Literature data The temperature distribution of a protected steel element under natu-ral fire can calculated with the Fourier Equation (5): ∂ ∂x λ ∂T ...
ing dehydration degree in the gypsum at this P–T condition. In the later stage (t>14 min), the transformation-time curve tended to be flat because the dehydration of gypsum was close to be ...
performed on Volterra gypsum in a triaxial apparatus, at various confining pressures and differential stresses. The tests presented here consisted of a regular increase in tem-perature from room temperature to 150 C, at constant con-fining and differential stress. No deformation was prescribed in addition to that induced by the dehydration reaction
Hydrothermal AFM has been used to study the thermal dehydration reaction on gypsum (010) surfaces in solutions at different saturation states, and in the absence …
Gypsum quantitative determination in cements may be done from their thermogravimetric analysis (TG) data, which uses the mass of the water released from its gypsum dehydration during cement analysis, to determinate its content stoichiometrically. Depending on the operational conditions used to mill the gypsum with clinker, its partial …
Thermal behaviour and kinetics of dehydration of gypsum in air have been investigated using in situ real-time laboratory parallel-beam X-ray powder diffraction data evaluated by the Rietveld method. Thermal expansion has been analysed from 298 to 373 K. The high-temperature limits for the cell edges and for the cell volume, calculated …
2.2. Triaxial Apparatus [8] The deformation apparatus used for our experiments is an externally heated triaxial oil medium cell [cf. Brantut et al., 2011; Ougier-Simonin et al., 2011].The confining pressure P c is directly applied by a volumetric servo pump, and measured by a pressure transducer with an accuracy of 10 −3 MPa. The …
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 ...
Download scientific diagram | Pressure^temperature graph showing the gypsum-out curve from Zen (1965), the metastable bassanite-in curve of McConnell et al . (1987), 30 8 C km À 1 and 15 8 C km ...
An in situ dehydration kinetics study of gypsum under water-saturated condition was performed in the temperature and pressure ranges of 383-423 K and 343-1085 MPa by using a hydrothermal …
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 …
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 …
When gypsum is subjected to a high temperature environment, water molecules bound in its crystal lattice are released and transferred through its mass; this "gypsum dehydration" (GD) process is highly endothermic, thus enhancing the fire resistance of the overall structure [5]. Despite the widespread use of GP wall assemblies …
(b) Mass vs. temperature curves of gypsum during heating as measured by TGA. Two different measurements were performed, one with a closed pan ( 50 μ m pinhole lid) and one with an open pan. Samples were …
1. Introduction1.1. General context. Gypsum plaster is an inorganic binder that is prepared in a two-step process. The first step is dehydration: heated to 100–200 °C, gypsum (CaSO 4 ·2H 2 O) releases water as vapor [1, 2] and, depending on temperature and water vapor partial pressure (p H2O) [3, 4] forms either hemihydrate (CaSO 4 •½H 2 …
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 …
(a and b) Load‐Displacement curves for linear loading‐rates and constant strain‐rates tests vary with temperature: 30°C–110°C shows pop‐ins during loading; 120°C–140°C shows smooth ...
In 2023, the Omani gypsum and anhydrite market was finally on the rise to reach $130M for the first time since 2020, thus ending a two-year declining trend. Overall, consumption showed a significant increase. Gypsum and anhydrite consumption peaked at $165M in 2020; however, from 2021 to 2023, consumption failed to regain momentum.
Considering the B1-B2 interface, time–temperature curves of specimen BR-SGP-S4 as an example (Fig. 10), at the beginning of the fire test, due to the large amount of heat absorbed through heating-induced dehydration and water evaporation of the fire-side gypsum boards, the time–temperature curve of the B1-layer, gypsum board cold …
Figure 1: a) Transverse nuclear magnetisation as a function of time as measured in saturated gypsum. In the inset: inverse Laplace transform of the exponential decay curve, revealing two dominant relaxation regimes. b) Schematic representation of the porous structure of gypsum, adapted from [5]. The pore structure is built up from …
In this work, the dehydration pathways of gypsum and the rehydration mechanism of soluble anhydrite were mainly investigated by thermodynamic modeling …
We are a consortium of the leading natural gypsum producers in the Sultanate of Oman. The member companies have created a synergy between them to cater to the global market. Our Services. Contact us. P.O.Box : 2236, P.C: 211, Salalah, Oman +968 23369555. info@sigoman. About. About me;
This article addresses the thermal properties and the microstructure of gypsum boards produced from β-hemihydrate by studying its dehydration process. …
Methods. The dehydration process of FGD gypsum was performed with simultaneous TG/DSC analysis (NETZSCH STA 409 Luxx, Selb/Bavaria, Germany) at N 2 atmosphere with a gas flow of 20 mL min −1.Non-isothermal analysis was carried out at different heating rate (2−20 K min −1).Isothermal analysis was conducted in the …
and/or mass loss rate as a function of time and/or temperature (see Fig. 1 for an example). 0.0 0.2 0.4 0.6 0.8 1.0 0 20 40 60 80 100 0 200 400 600 800 1000 / ° C)) Temperature ( °C) Fig. 1. Example of TGA mass and mass loss rate curves (Type C gypsum board heated at 20 °C/min). ARRHENIUS-RATE THERMAL DECOMPOSITION KINETICS
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 …
Thermal conductivity of gypsum boards beyond dehydration temperature. K. Ghazi Wakili, Corresponding Author. K. Ghazi Wakili. Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland.
Temperature measurements at pre-selected board locations indicated three distinct stages of gypsum dehydration; free moisture evaporation, transformation of calcium sulfate dihydrate to calcium ...
Introduction. Gypsum plaster is an inorganic binder that is prepared in a two-step process. The first step is dehydration: heated to 100–200 °C, gypsum (CaSO 4 ·2H 2 O) releases water as vapor [1,2] and, depending on temperature and water vapor partial pressure (p H2O) [3,4] forms either hemihydrate (CaSO 4 •½H 2 O) or γ-anhydrite …
The fastest growing export markets for Gypsum of Oman between 2021 and 2022 were India ($25.7M), Nepal ($2.29M), and Indonesia ($1.5M). Imports In 2022, Oman imported $559k in Gypsum, becoming the 130th largest importer of Gypsum in the world. At the same year, Gypsum was the 854th most imported product in Oman.
Temperature measurements at pre-selected board locations indicated three distinct stages of gypsum dehydration; free moisture evaporation, transformation of …
The performance of composite gypsum at elevated temperatures depends on the treatment temperature and reflects the combined effects of gypsum phase change and the filler effects of silica flour or talc powder. ... There was tremendous pore water loss, and gypsum dehydration happened at 100 °C and 200 °C, leading to a porous …
Possible transformations of the dehydration and hydration of synthetic gypsum in the calcination process [23]. …
