Hydration of Gypsum Plaster

Cunningham, William A.; Dunham, R. M.; Antes, L. L.

doi:10.1021/ie50514a035

Cited by 11 publications

(2 citation statements)

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“…In nature the calcium sulfate is found in three phases distinguished by the degree of hydration: gypsum (CaSO 4 ⋅2H 2 O), bassanite or hemihydrate (CaSO 4 ⋅0.5H 2 O) and anhydrite (CaSO 4 or γ-CaSO4) (Cunningham et al, 1952;Freyer and Voigt, 2003). After CaCO 3 or CaMg(CO 3 ) 2 reacting with sulfide, bassanite will become the stable precursor phase to gypsum precipitation firstly (Wang et al, 2012;Van Driessche et al, 2012;Stawski et al, 2016), when the concentration increasing due to water evaporating in the water-remaining area on sculptures.…”

Section: Black Crust Forming Mechanism Discussionmentioning

confidence: 99%

Study on the mechanism of the black crust formation on the ancient marble sculptures and the effect of pollution in Beijing area

Wang

Li³

et al. 2022

Heliyon

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Section: Black Crust Forming Mechanism Discussionmentioning

confidence: 99%

Study on the mechanism of the black crust formation on the ancient marble sculptures and the effect of pollution in Beijing area

Wang

Li³

et al. 2022

Heliyon

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“…Photomicrographic (1) and radioisotope (3) studies support this view, which has been discussed in relation to the theory of von Weinlarn (2,4). Some worlcers have suggested that the rate of solution of the hemihydrate is the controlling factor and that retarders function by affecting this rate of solution.…”

Section: Introductionmentioning

confidence: 93%

The Crystallization of Calcium Sulphate Dihydrate

Schierholtz¹

1958

Can. J. Chem.

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In this preliminary series of experiments, calcium sulphate dihydrate has been allowed t o crystallize spontaneously from solutions of varying degrees of supersaturation, and induction periods and rate constants have been determined. The effect of crystal area, pH, and accelerators and retarders on this process has been examined. T h e degree of supersaturation has a direct effect on both the induction period and rate constant. Nucleation is affected marlcedly by pH. Salts having an ion in common with calcium sulphate function as accelerators. Retarders affect the induction period in proportion to their concentration, but show little, if any, effect or1 the rate of crystallization. The behavior of the various reagents under the conditions prevaili~lg in these experiments is largely in accord with observations on the behavior of commercial plasters. INTRODUCTIONThe work described in this paper was undertaken because of the apparent conflict of explanations offered in the literature for some of the phenomeila observed in the setting of commercial gypsum plasters, which ilzvolves the crystallization of calcium sulphate dihydrate. A clearer understanding of the fuizctioil of accelerators and retarders would be of considerable value in the manipulation of commercial plasters for specific purposes.The results of several previous studies (1, 2, 3) indicate that the hemihydrate dissolves to form a solution supersaturated with respect to the dihydrate, which then crystallizes out. Photomicrographic (1) and radioisotope (3) studies support this view, which has been discussed in relation to the theory of von Weinlarn (2, 4). Some worlcers have suggested that the rate of solution of the hemihydrate is the controlling factor and that retarders function by affecting this rate of solution.In this paper, the first of a series, the reactants were all in solution initially, thus eliminating any effects attributable to the surface of the heinihydrate or its rate of solution. T h e influence of such factors as the initial supersaturation, crystal surface area of the dihydrate, pH, and addition of accelerators and retarders was then determined. T h e effect of temperature was not investigated a t this time, hence the calculation of activation energies has not been attempted.The first attempts to obtain solutioils supersaturated with respect to calcium sulphate dihydrate were b y dissolving hemihydrate a t 10°C. and raising the temperature to 25' C. This was based on solubility data reported in the literature (5, 6). Because of difficulty in achieving complete, rapid solution of the hemihydrate, this method was abandoned i11 favor of the following.The calcium required for any desired supersaturation was weighed out as calcium hydroxide, dispersed in a little water, the equivalent amount of standard sulphuric acid added, and the solution made to final volume of 150 cc. with water. After thorough stirring, the solutio~z was filtered through Whatman No. 41H paper into an aluminum dish. All these operations were performed a t 10' C. The ...

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Technology of Major Wood‐ and Fiber‐Based Composites: An Overview

Stokke

Han

2013

Introduction to Wood and Natural Fiber Composites

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Hydration of Gypsum Plaster

Cited by 11 publications

References 3 publications

Study on the mechanism of the black crust formation on the ancient marble sculptures and the effect of pollution in Beijing area

Study on the mechanism of the black crust formation on the ancient marble sculptures and the effect of pollution in Beijing area

The Crystallization of Calcium Sulphate Dihydrate

Technology of Major Wood‐ and Fiber‐Based Composites: An Overview

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