The temperature at which the gypsum binder (calcium sulfate hemihydrate) is industrially produced, between 80 and 180 °C, is often mentioned in the literature …
WhatsApp: +86 18221755073
This article investigates the thermal performance of gypsum boards in the dehydration temperature region, where pronounced chemical reactivity is anticipated. Gypsum board samples were gradually ...
WhatsApp: +86 18221755073
The above process, known as "dehydration" or "calcination" of gypsum, takes place at the temperature range between ∼80 °C and ∼250 °C, depending on the heating rate, of the gypsum board, and its composition [1], [10], [11].
WhatsApp: +86 18221755073
Gypsum wallboard has been used for over 100 years as a barrier to the spread of fire in residential and commercial structures. The gypsum molecule, CaSO 4 ·2H 2 O, provides two crystalline waters that are released upon heating providing an endothermic effect. Manufacturers have recognized that the source of the gypsum ore …
WhatsApp: +86 18221755073
When hardened gypsum is exposed to the elevated temperature, the dehydration starts at the temperature about 60 °C . The dehydration is usually two-step process; firstly, the calcium sulphate hemihydrate is formed and later anhydrite, usually at temperatures below 200 °C. Both steps take place in a relatively wide temperature …
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 …
WhatsApp: +86 18221755073
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 …
WhatsApp: +86 18221755073
Abstract. 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 diamond anvil cell and Raman spectroscopy. Kinetic analysis shows that the dehydration rate k increases with pressure, suggesting …
WhatsApp: +86 18221755073
ture at which the dehydration events occur increases (T dehydration = 425.5 K in an open system, T dehydration = 439 K in a sealed system, in the presence of excess water). …
WhatsApp: +86 18221755073
The dependence of the solubility of gypsum on temperature is nonlinear, reaching a maximum at 43°C. ... the dehydration of gypsum due to the effects. of high pressure and temperature during ...
WhatsApp: +86 18221755073
To obtain the dehydration rate of gypsum at certain temperature ... Figure 3. A series of Raman spectra as a function of time acquired during gypsum dehydration at 393 K and 421 MPa.
WhatsApp: +86 18221755073
The first describes the process of water leaving the structure of gypsum to form hemihydrate or anhydrite. The second depicts the temperature-dependent solubility of the calcium sulphates in water. The third illustrates the hydration energy of hemihydrate as it reacts with water. Diagram 1 - Dehydration
WhatsApp: +86 18221755073
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 ...
WhatsApp: +86 18221755073
DOI: 10.1002/fam.2234 Corpus ID: 135782591; Thermal conductivity of gypsum boards beyond dehydration temperature @article{GhaziWakili2015ThermalCO, title={Thermal conductivity of gypsum boards beyond dehydration temperature}, author={Karim Ghazi Wakili and Matthias M. Koebel and T. Glaettli and Marco Hofer}, journal={Fire and …
WhatsApp: +86 18221755073
Dehydration Temperature of Gypsum. Keiichi MURAKAMI, Yosihisa SHIMAMURA, Hirobumi TANAKA. Author information ... In an atomsphere, the primary dehydration temperature of natual dihydrated gypsum used as a test sample is 133°C while its secondary dehydration temperature being 192°C. Under pressure of saturated water …
WhatsApp: +86 18221755073
of Gypsum Rock During High-Temperature Dehydration–Hydration Expansion Sijiang Wei,1,2 Yushun Yang,3,5 Chongbang Xu,4 Meng Wang,1,2 Wenlong Shen,1,2 and Chengdong Su1,2 ... temperature dehydrated gypsum rock was treated with different hydration time, and the gypsum rock samples in three states were subjected to …
WhatsApp: +86 18221755073
LTP (at room temperature) contains abundant high-energy electrons in the range of 1~10eV [2] with higher ... And gypsum dehydration is the significant process of CO 2 LTP weathering. However, the other changes in composition and structure of sam-ples were not detected using our Raman method.
WhatsApp: +86 18221755073
Jacques et al. [26] found that the dehydration temperature of waste gypsum is lower than that of pure gypsum, implying that the presence of impurity ion might lower the dehydration temperature for ...
WhatsApp: +86 18221755073
changes (1-2 min) as a function of temperature. a b Figure 1. a) Dehydration of gypsum at 85 °C and 17.6% RH. Reaction starts in <1 hr and is complete after 5.6 hr. b) Dehydration of gypsum at 85 °C and 47% RH. Reaction starts after 6.6 hr and is close to completion after 50 hr. Lunar and Planetary Science XXXVIII (2007) 1432.pdf
WhatsApp: +86 18221755073
DEHYDRATION OF GYPSUM. Studies of the dehydration of gypsum in dry air atmospheres have shown that the hemihydrate of calcium sulfate is not a stable phase in the temperature range 90-140 deg C. The final product of dehydration was always anhydrous. Discontinuities in the weight loss versus time curves for powdered gypsum …
WhatsApp: +86 18221755073
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 …
WhatsApp: +86 18221755073
For example, Yang et al. found that the dehydration temperature of gypsum gradually increased with the rise in pressure, and the dehydration boundary between gypsum and bassanite was determined to ...
WhatsApp: +86 18221755073
The dehydration products of gypsum under different temperature and water vapor pressure were investigated by …
WhatsApp: +86 18221755073
It can be postulated that dehydration of gypsum at a temperature of 85 °C for 120 h almost exclusively leads to bassanite (96 wt.% bassanite, 4 wt.% anhydrite II). The reverse reaction must be kinetically hindered as no …
WhatsApp: +86 18221755073
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 diamond ...
WhatsApp: +86 18221755073
Synthetic anhydrite is obtained when gypsum is dehydrated at the temperature of 600 to 800ºC [7]. There is little knowledge about the influence of the dehydration temperature on
WhatsApp: +86 18221755073
One way to overcome part of the technical difficulties when dealing with high-pressure and high-temperature tests is to study gypsum as an analogue of serpentine-rich rocks at depth [Ko et al., 1997; ... The …
WhatsApp: +86 18221755073
gypsum-anhydrite dehydration reaction sequences at simultaneous high-pressure and temperature conditions. Mirwald (2008) performed a study of CaSO 4 H 2O system by differential pressure analysis (DPA), following the dehydration process up to 623 K and 3.5 GPa and deter-mined the dehydration boundaries of gypsum-bassanite and
WhatsApp: +86 18221755073
Low-temperature dehydration of gypsum single crystals. 2008 • Nailia Khasanova. Download Free PDF View PDF. Structure and microstructure of gypsum and its relevance to Rietveld quantitative phase analyses. 2004 • Santiago García-Granda.
WhatsApp: +86 18221755073
This article investigates the thermal performance of gypsum boards in the dehydration temperature region, where pronounced chemical reactivity is anticipated. Gypsum board samples were gradually ...
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 …
WhatsApp: +86 18221755073حقوق النشر والنسخ؛ 2024.Aava جميع الحقوق محفوظة.خريطة الموقع