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during dehydration. In particular, Popp and Kern [1993] observed dramatic decreases in V P, V S and Poisson's ratio during experimental dehydration of lizardite and gypsum. [3] Two challenging problems encountered in addressing the possible importance of dehydration embrittlement in 1Laboratoire de Géologie, École Normale Supérieure, …
RESEARCH RESEARCHCOMMUNICATIONS COMMUNICATIONS In situ micro-Raman investigation of dehydration mechanism in natural gypsum P. S. R. Prasad†,*, A. Pradhan‡ and T. N. Gowd† † Mineral Physics …
The thermodynamic calculation results reveal that γ-CaSO4 has an extraordinary ability to capture water molecules from an extremely dry atmosphere, which is very useful in some fields, such as in drying processes and even for extracting liquid water fromextremely dry atmosphere. The dehydration products of gypsum under different …
Table 3 Average value of the activation energy of gypsum dehydration for the steps, which can be seen in Fig. 4 E/kJ molŒ1 216 184 238 117 αstep 0.08Œ0.24 0.24Œ0.51 0.52Œ0.72 0.72Œ0.92 Step number I II III IV The first step, in the range of the low values of αis characterised by relatively
The dehydration mechanism of natural single crystals of gypsum was investigated in the temperature range 300-430 K by in situ infrared (FTIR) spectroscopy. The thermal evolution of the second-order modes of H 2 O and SO 4 groups in gypsum, in the wavenumber range 4850.5450 cm -1 and 2050.2300 cm -1 respectively, were used …
The microstructures of a set of samples containing bassanite and gypsum from dehydration experiments on Volterra gypsum have been analysed by conventional transmitted light microscopy and electron ...
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 the global use of plaster ...
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 at …
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 …
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 °C. When mixed with water, it dissolves while new gypsum crystals precipitate. Plaster's microstructures affect its reactivity and setting properties, but are poorly understood due …
695 Neomorphism of the Middle Devonian Ratner limestone related to dehydration of gypsum in south-central Saskatchewan Qilong Fu and Hairuo Qing Abstract: The Middle Devonian Ratner Formation in south-central Saskatchewan consists of laminated carbonate and interlaminated to interbedded carbonate and anhydrite, and the Ratner carbonate is …
Abstract for 11th GeoRaman International Conference, June 15-19, 2014, St. Louis, Missouri, USA THE MICRO RAMAN SPECTROSCOPY FOR ANALYSIS OF THE GYPSUM DEHYDRATION BY SIMULATED SPACE WEATHERING. Zhongchen Wu1,2, Yuheng Ni1, Zongcheng Ling1, Hong Wu1.1School of Space Science and Physics & …
Diagram 1 - Dehydration. The first process is the formation of hemihydrate or anhydrite from dihydrate. To obtain more information about this step, gypsum crystals were grown from sodium sulphate and calcium chloride via a diffusion process. A large test tube, approximately 200mL in volume, was filled with 3g of sodium sulphate (Na 2 SO 4).
Oman: Oman exported 11.2Mt of natural gypsum from its Port of Salalah in 2023, up by 11% year-on-year from 9.9Mt in 2022. Zawawi Minerals has reported that the main destination for exports was …
This work firstly shows that the observed crystallization inside of gypsum during dehydration is the formation of alpha-hemihydrate. Gypsum crystal at (a) 135 • C, and (b) 142 • C. Crystals ...
Gypsum: Oman is the world's largest gypsum exporter by weight, shipping approximately 8.74 million tons in 2021 primarily to ASEAN and South/East African countries, according to local press. Chromite: Approximately 30 million metric tons of chromite ore are in Oman, according to the Oman Chromite Company. Oman is …
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). Compared with the wealth of high-temperature studies available, there is a lack of experimental studies on the gypsum-anhydrite dehydration reaction sequences at
"Going forward, importing countries will be increasingly looking to the Sultanate of Oman to meet their gypsum requirements. At the current rate of growth in exports, Oman's share is projected to rise to around 48 - 50 per cent of demand, which equates to over 130 million MT over the 2022- 2031 timeframe." ...
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 weakens the rock, facilitating deformation. In our study, we employ microindentation tests to examine the micromechanics of gypsum during …
dehydration products of gypsum. Of particular interest in our context is the work of Bensted and Prakash (1968) who investigated the possibility of the existence of two forms of hemihydrate (c~ and/3), but concluded that there are only three dehydration products of the dehydration of gyp-
The gypsum dehydration capability determined under the given test conditions of about 26% in the vertical stirred media mill can be considered as relatively low compared with the dehydration capability of ball mills (up to ). Comparable grinding trials in a semi-industrial horizontal SMM have shown that with fairly long operating times ...
The dehydration process of gypsum rock was studied under concentrated solar energy by using a Fresnel lens with power density of 260 Wcm 2. Temperatures higher than 700 C were attained for 1 min ...
paper uses advanced poromechanics to investigate the dehydration of gypsum when subjected to heating. The proposed approach includes the fundamental principles of …
Key Points. Dehydration of gypsum in drained conditions induces a decrease in Vp and Vs. Acoustic emissions indicate pore collapse. Poisson's ratio …
In order to study the physical and mechanical properties of gypsum rock samples in three states (natural, high-temperature dehydration and hydration time), natural gypsum rock was put into high-temperature condition of 220°C for dehydration treatment, and then the high-temperature dehydrated gypsum rock was treated with different …
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 the global use of plaster ...
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 …
to gypsum with an associated vol-ume increase of up to 63%, whereas gypsum dehydration results in a reversal back to anhydrite that leads to 39% volume decrease. Swelling and compressibility problems are common in several coastal deposits of the globe. This paper investigates the geological and engineering as-pects of anhydrite/gypsum …
In this work, the dehydration pathways of gypsum and the rehydration mechanism of soluble anhydrite were mainly investigated by thermodynamic modeling …
Mineralogical Magazine, June 2009, Vol. 73(3), pp. 421–432 Structural evolution during the dehydration of gypsum materials S. D. M. JACQUES1,*, A. GONZÁLEZ-SABORIDO1, O. LEYNAUD1, J. BENSTED1, M. TYRER2, R. I. W. GREAVES2 AND P. BARNES1 1 Department of Chemistry, University College London, 20 Gordon Street, …