MENU
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 …
WhatsApp: +86 18221755073
The degree of dehydration depends on the temperature and duration of heating. Partial Dehydration: When gypsum is partially dehydrated, it forms a material known as "plaster of Paris" or "calcined gypsum." Plaster of Paris is a white, powdery substance that can be mixed with water to create a workable plaster paste, used in …
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
At 2.5 GPa, gypsum starts to dehydrate around 428 K, by forming bassanite, CaSO4 hemihydrate, which completely dehydrates to c-anhydrite at 488 K.
WhatsApp: +86 18221755073
At 2.5 GPa, gypsum starts to dehydrate around 428 K, by forming bassanite, CaSO4 hemihydrate, which completely dehydrates to γ-anhydrite at 488 K.
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
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. ... No consistent relationship was observed between dehydration temperature and grain size or ...
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
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 …
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
Although high-temperature calcination (≥800°C) could destroy the gypsum structure [10] to release the incorporated metals ... 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 …
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
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
Abstract The dehydration of gypsum CaSO4.2H2O has been studied, at negligible water vapour pressure, by in situ infrared (IR) spectroscopy and by thermogravimetry to determine whether intermediate phases (CaSO4.nH2O) exist, other than the hemihydrate with n=0.5, and also to compare the mechanism of the …
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
Structural evolution during the dehydration of gypsum materials - Volume 73 Issue 3. ... J.D. and Hinks, D.G. (1984) A crystallographic study of the low-temperature dehydration products of gypsum, CaSO 4-2H 2 O; hemihydrate CaSO 4-0.5H 2 O, and γ-CaSO 4. American Mineralogist, 69, 910—919.Google Scholar.
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 …
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
In this work, the dehydration pathways of gypsum and the rehydration mechanism of soluble anhydrite were mainly investigated by thermodynamic modeling …
WhatsApp: +86 18221755073
The thermodynamic calculation results reveal that the dehydration mechanism of gypsum significantly depended on ambient temperature and water vapor pressure.
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.
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 18221755073
The dehydration kinetics of gypsum strongly depend on temperature and water vapour pressure. Here, we perform fast, time- ... effect of mechanical stress on gypsum dehydration kinetics is not well ...
WhatsApp: +86 18221755073
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 …
WhatsApp: +86 18221755073
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 content, evaporates.
WhatsApp: +86 18221755073
The commercial rock gypsum studied generates both hemihydrate and anhydrite at 128°C, and its impurities do not dehydrate until the temperature is increased to 500°C.
WhatsApp: +86 18221755073
Mass losses vary between 13.7 and 16.5% and heat of dehydration values between 377 and 420 J g −1 for the dehydration of ground and mixed inhomogeneous gypsum samples. As for the dehydration of CaSO 4 ·2H 2 O, the dehydration of synthetic gypsum proceeds via multi-step reactions. Using a heating rate of 5°C min −1, the very …
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 test results of water absorption during high-temperature dehydration gypsum rock immersion and hydration are shown in Figure 9a. It can be seen that the hydration water absorption rate increased rapidly within 0–20 min, and the water absorption amount and the water absorption time were in a logarithmic relationship; after 20 min, …
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 18221755073Copyright © 2024 Sofol Industry & Technology Group Co., Ltd.
المنتجات
محلول
حول الولايات المتحدة
اتصل بنا