Low-temperature dehydration of gypsum single crystals

Khasanov, R. R.; Nizamutdinov, N. M.; Khasanova, N. M.; Губайдуллин, А. Т.; Vinokurov, V. M.

doi:10.1134/s1063774508050143

Cited by 6 publications

(3 citation statements)

References 7 publications

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“…7), reflecting minor structural variations at these temperatures. The identification of this hydro g-anhydride stage is coherent with the structure mentioned by Bezou 35 and studied by Khasanov 69 using electron spin resonance (ESR) techniques.…”

Section: View Article Onlinesupporting

confidence: 81%

“…Also, in the dehydrated g-anhydride stage, the free electric charges along the structure's channels are suitable for ionic polarizability. The presence of SO 3 À radical ion molecules, particularly in g-anhydride, was detected by ESR, 69 these molecules contributing to the ionic heating. After the structural recrystallization to b-anhydride, with a more balanced distribution of the charges, this ionic mechanism is reduced.…”

Section: Identified Mechanisms Of Microwave Absorptionmentioning

confidence: 98%

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Evidence of a new phase in gypsum–anhydrite transformations under microwave heating byin situdielectric analysis and Raman spectroscopy

López-Buendía

García-Baños

Urquiola

et al. 2020

Phys. Chem. Chem. Phys.

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Section: View Article Onlinesupporting

confidence: 81%

Section: Identified Mechanisms Of Microwave Absorptionmentioning

confidence: 98%

Evidence of a new phase in gypsum–anhydrite transformations under microwave heating byin situdielectric analysis and Raman spectroscopy

López-Buendía

García-Baños

Urquiola

et al. 2020

Phys. Chem. Chem. Phys.

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“…Due to the bound water in the structure, gypsum crystals undergo dehydration at relatively low temperatures, resulting in the formation of several progressive phases of metastable calcium sulphate accompanied by a change in chemical structure and volume (Posnjak, 1938;McConnell et al, 1987;Horta, 1989;Carbone et al, 2008;Jacques et al, 2009;Khasanov et al, 2008). There are three recognisable phases in the CaSO 4 -H 2 O system; namely gypsum, hemihydrate (commonly known as bassanite used as Plaster of Paris, CaSO 4 •½H 2 O) and anhydrite (CaSO 4 ) (Seufert et al, 2009).…”

Section: -mentioning

confidence: 99%

Hydrogeological Properties of Gypseous soils in South Africa

Greyling

Rooy

2019

South African Journal of Geology

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Gypseous soils occur in the western arid and semi-arid regions of South Africa and Namibia. These soils exhibit a complex nature and abnormal behaviour due to their gypsum content and as such they have become more prevalent in research. As these soils are finding more use in industry, an astute understanding of their hydrogeological properties and behaviour is required. Powdery gypseous soil samples collected from the Northern Cape (Geelvloer) and Western Cape (Rooiberg and R355) Provinces, as well as a prepared sample, are subject to XRD analysis, particle size distribution determination and falling-head permeability tests using both water and brine. The testing served as preliminary research to guide further studies into the topic. The prepared sample, with 19% fines, comprises 35% gypsum and 65% sand. Geelvloer samples, with 91.95% gypsum content, are comprised mostly of sand-sized particles with 45% fines. Rooiberg samples contain 75% fines with a slightly lower gypsum content of 83.25%, while R355 samples have 50% fines with 75.35% gypsum. It is generally understood that particle size distribution contributes to the hydraulic conductivity of soils, where a higher portion fines will result in a lower conductivity. In the case of gypseous soils, the solubility is of importance as well, as it may have long term effects. With the intent of evaluating the effect of the aforementioned factors on the hydraulic conductivity of gypseous soils in South Africa, the samples taken represent differences in particle size distribution and origin. Geelvloer had k-values in the order of 8.82×10-6 m/s, with the brine sample giving 9.43×10-6 m/s, while the k-values for Rooiberg and R355 were in the order of 3.90×10-6 m/s and 5.87×10-6 m/s, respectively. The brine resulted in 5.63×10-6 m/s for Rooiberg and 9.90×10-6 m/s for the R355 sample. The made sample, having less fines, had k values in the order of 2.15×10-5 m/s, and 4.19×10-5 m/s for the brine. The differences between the results are largely negligible and show that despite what is believed to influence the hydraulic conductivity, in the case of gypseous soils in South Africa, on a small scale, it remained unaffected.

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Temperature and humidity dependent formation of CaSO4·xH2O (x = 0...2) phases

Ritterbach

Becker

2020

Global and Planetary Change

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Low-temperature dehydration of gypsum single crystals

Cited by 6 publications

References 7 publications

Evidence of a new phase in gypsum–anhydrite transformations under microwave heating byin situdielectric analysis and Raman spectroscopy

Evidence of a new phase in gypsum–anhydrite transformations under microwave heating byin situdielectric analysis and Raman spectroscopy

Hydrogeological Properties of Gypseous soils in South Africa

Temperature and humidity dependent formation of CaSO4·xH2O (x = 0...2) phases

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