Use of compacts to study the sorption characteristics of powdered plaster of Paris

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TypeArticle
Journal titleJournal of Applied Chemistry
ISSN0021-8871
Volume13
Issue4
Pages158167; # of pages: 10
Subjectgypsum plaster; water vapor; water absorption; isotherms; Concrete; platre; vapeur d'eau; absorption d'eau; isotherme
AbstractCompacts made from powdered material are used in an effort to explain anomalous results obtained from the isothermal uptake of water vapour by various types of dehydrated gypsum. In the sorption isotherms, a sharp discontinuity occurred at R.H. between 0.25 and 0.40 and a secondary hysteresis was observed. Sorption of methanol on these materials was also measured, and results were compared with those obtained with water. The determination of the expansion isotherm enabled an application of the Gibbs adsorption equation to be made, which led to a method by which it was possible to differentiate between hemihydrate and adsorbed water and thus allow a calculation of a B.E.T. surface area from the water isotherm for the material. From this calculation and others obtained by use of a modified Kelvin equation, it was concluded that the anomalies noted above were due to sites on the surface of the plaster that required an activation energy for `sorption' to occur. The generation of these sites was considered dependent on the method of preparation of the anhydrous calcium sulphate. The water attached to these sites would thus be termed ` chemisorbed' water.
Publication date
LanguageEnglish
AffiliationNRC Institute for Research in Construction; National Research Council Canada
Peer reviewedNo
IdentifierDBR-RP-188
NRC number7331
3361
NPARC number20375339
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Record identifier0644dbcf-c4f5-436b-983e-3764de2944ca
Record created2012-07-23
Record modified2016-05-09
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