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hemihydrate

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Journal Article

Thermal behaviour and kinetics of dehydration in air of bassanite, calcium sulphate hemihydrate (CaSO 4 ·0.5H 2 O), from X-ray powder diffraction

Paolo Ballirano, Elisa Melis
Published: 01 October 2009
European Journal of Mineralogy (2009) 21 (5): 985–993.
DOI: https://doi.org/10.1127/0935-1221/2009/0021-1973
...Paolo Ballirano; Elisa Melis Abstract Thermal behaviour and kinetics of dehydration in air of bassanite (calcium sulphate hemihydrate, CaSO 4 ·0.5H 2 O) have been investigated in situ real-time using laboratory parallel-beam X-ray powder diffraction data. Thermal expansion has been analyzed between...
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The monoclinic I 2 structure of bassanite, calcium sulphate hemihydrate (CaSO 4 · 0.5H 2 O)

Paolo BALLIRANO, Adriana MARAS, Simone MELONI, Ruggero CAMINITI
Published: 01 September 2001
European Journal of Mineralogy (2001) 13 (5): 985–993.
DOI: https://doi.org/10.1127/0935-1221/2001/0013-0985
... axis b ), cell parameters a = 12.0350(5) Å, b = 6.9294(3) Å, c = 12.6705(4) Å, β = 90.266(3)°. The structure of the hemihydrate is strongly pseudo-trigonal, space group P 3 1 21. The symmetry lowering arises from water molecules ordering inside the channels. e-mail: [email protected]...
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A crystallographic study of the low-temperature dehydration products of gypsum, CaSO 4 · 2H 2 O: hemihydrate, CaSO 4 · 0.50H 2 O, and γ-CaSO 4

G. A. Lager, T. Armbruster, F. J. Rotella, J. D. Jorgensen, D. G. Hinks
Published: 01 October 1984
American Mineralogist (1984) 69 (9-10): 910–919.
... ) and 12.10 (Rietveld R ). The observed neutron powder profile for hemihydrate (CaSO 4 · 0.50D 2 O) is qualitatively consistent with a model in which the water molecules occupy two different levels in the channels of a distorted γ –CaSO 4 framework. Hemihydrates formed by dehydration of gypsum (CaSO 4 · 2H 2...
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A continuous X -ray investigation using an autoclave of the conversion of gypsum to hemihydrate

John B. Droste, Ralph E. Grim
Published: 01 August 1959
American Mineralogist (1959) 44 (7-8): 731–737.
... to hemihydrate. Temperature and steam pressure conditions necessary and favorable for the conversion are given, and it is suggested that there is no intermediate step in the transition. 27 10 1958 Copyright © 1959 by the Mineralogical Society of America 1959 Mineralogical Society of America ...
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Note on the occurrence of calcium sulphate hemihydrate (CaSO 4 · 1/2 H 2 O) in thin sections of rocks

Charles Milton
Published: 01 July 1942
American Mineralogist (1942) 27 (7): 517–518.
...Charles Milton Abstract The partial dehydration of gypsum to the hemihydrate with the loss of one and a half of the two water molecules of gypsum has been studied by many investigators, a recent and definitive paper being that by E. Posnjak. As the transformation of the gypsum to the hemihydrate...
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(a) Compressive strength variation trend with different drying time; (b) pe...

(a) Compressive strength variation trend with different drying time; (b) pe...

Published: 27 December 2021
Fig. 15. (a) Compressive strength variation trend with different drying time; (b) percentage of water evaporation with respect to the initial amount in weight, monitored through time during the drying stage and (c) compressive strength values for different concentrations of hemihydrate in sand
Journal Article

Structural evolution during the dehydration of gypsum materials

S. D. M. Jacques, A. González-Saborido, O. Leynaud, J. Bensted, M. Tyrer, R. I. W. Greaves, P. Barnes
Published: 01 June 2009
Mineralogical Magazine (2009) 73 (3): 421–432.
DOI: https://doi.org/10.1180/minmag.2009.073.3.421
...; various industrial waste gypsums were also studied under a common standard environment. 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...
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( a ) Unit-cell volume of the <span class="search-highlight">hemihydrate</span> phase during the dehydration stud...

( a ) Unit-cell volume of the hemihydrate phase during the dehydration stud...

Published: 01 June 2009
F ig . 4. ( a ) Unit-cell volume of the hemihydrate phase during the dehydration study of pure gypsum within a sealed capillary with an excess of water. ( b ) View of the ab plane of the hemihydrate structure with 0.5 water molecules content at 230°C. The crystal structure data can be found
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Crystal structure of <span class="search-highlight">hemihydrate</span> MoO 3 ·1&#x2F;2H 2 O ( Bénard et al . (1994) ....

Crystal structure of hemihydrate MoO 3 ·1/2H 2 O ( Bénard et al . (1994) ....

Published: 10 March 2023
Fig. 9. Crystal structure of hemihydrate MoO 3 ·1/2H 2 O ( Bénard et al . (1994) . The aqua spheres and green and purple octahedra represent H 2 O, MoO 6 , and MoO 5 (H 2 O) groups, respectively.
Journal Article

The crystal forms of calcium sulphate

L. S. Ramsdell, E. P. Partridge
Published: 01 February 1929
American Mineralogist (1929) 14 (2): 59–74.
..., commonly called “soluble anhydrite,” has a crystal structure identical with that of the hemihydrate, and supports the hypothesis of Linck and Jung that the hemihydrate is zeolitic in nature, losing and regaining its water of hydration without change in crystal structure. An equilibrium system for the three...
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Uniaxial compression test results for sand–<span class="search-highlight">hemihydrate</span> and sand–vegetable o...

Uniaxial compression test results for sand–hemihydrate and sand–vegetable o...

Published: 27 December 2021
Fig. 6. Uniaxial compression test results for sand–hemihydrate and sand–vegetable oil samples: (a) compressive strength derived from the tests and (b, c) normal load (N) versus strain (%) curves.
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Ring-shear test diagrams (shear stress versus time) for sand–<span class="search-highlight">hemihydrate</span>, s...

Ring-shear test diagrams (shear stress versus time) for sand–hemihydrate, s...

Published: 27 December 2021
Fig. 8. Ring-shear test diagrams (shear stress versus time) for sand–hemihydrate, sand–vegetable oil samples and quartz sand BL60.
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Plots of mass versus volume for sand–<span class="search-highlight">hemihydrate</span> model material.

Plots of mass versus volume for sand–hemihydrate model material.

Published: 27 December 2021
Fig. 10. Plots of mass versus volume for sand–hemihydrate model material.
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DIC time-series images of sand–<span class="search-highlight">hemihydrate</span> 2% sample surface during GRAM te...

DIC time-series images of sand–hemihydrate 2% sample surface during GRAM te...

Published: 27 December 2021
Fig. 13. DIC time-series images of sand–hemihydrate 2% sample surface during GRAM test-7 experiment: (a) image source data; (b) structural map; (c) displacement field (mm) with vector displacement; (d) shear strain ϵ xy (%) with vectors displacement; and (e) z -displacement (mm) with vector
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Uniaxial compression test results for sand–<span class="search-highlight">hemihydrate</span> samples at different...

Uniaxial compression test results for sand–hemihydrate samples at different...

Published: 27 December 2021
Table 9. Uniaxial compression test results for sand–hemihydrate samples at different mixing ratios: 1%, 2%, 3% and 4%. The error is the standard deviation of the mean values after multiple measurements (a total of 53 samples were tested).
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α-<span class="search-highlight">hemihydrate</span>.

α-hemihydrate.

Published: 01 January 2012
Figure 66 α-hemihydrate.
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Unit-cell expansion of the <span class="search-highlight">hemihydrate</span> phase during the dehydration study o...

Unit-cell expansion of the hemihydrate phase during the dehydration study o...

Published: 01 June 2009
F ig . 3. Unit-cell expansion of the hemihydrate phase during the dehydration study of pure gypsum within a sealed capillary with an excess of water: ( A ) a, b and c unit-cell parameters; ( B ) β unit-cell angle. The absolute unit-cell values at 171°C are a = 12.0354(8) Å, b = 6.9319(4
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Occupancy of the <span class="search-highlight">hemihydrate</span> O(13) and O(14) oxygen atoms belonging to the ...

Occupancy of the hemihydrate O(13) and O(14) oxygen atoms belonging to the ...

Published: 01 June 2009
F ig . 5. Occupancy of the hemihydrate O(13) and O(14) oxygen atoms belonging to the water molecules together with the stoichiometric water content during the dehydration of pure gypsum within a sealed capillary with an excess of water. The water content is calculated as (2 * O(13)occ + 4 * O(14
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Raman spectrum of <span class="search-highlight">hemihydrate</span> powder in the OH- stretching region (3475 to ...

Raman spectrum of hemihydrate powder in the OH- stretching region (3475 to ...

Published: 01 February 2004
F igure 5. Raman spectrum of hemihydrate powder in the OH- stretching region (3475 to 3700 cm −1 ) produced from rehydration of heated gypsum in the high-temperature Raman studies.
Journal Article

Micro-Raman studies of gypsum in the temperature range between 9 K and 373 K

Chi Hong Chio, Shiv K. Sharma, David W. Muenow
Published: 01 February 2004
American Mineralogist (2004) 89 (2-3): 390–395.
DOI: https://doi.org/10.2138/am-2004-2-320
...F igure 5. Raman spectrum of hemihydrate powder in the OH- stretching region (3475 to 3700 cm −1 ) produced from rehydration of heated gypsum in the high-temperature Raman studies. ...
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