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Dissolution of CaSO4 dot 1/2H2O and precipitation of CaSO4 dot 2H2O - A kinetic study by synchrotron X-ray powder diffraction
Time-resolved X-ray powder diffraction has been performed on hydrating samples of calcium sulfate hemihydrate with 0.50 wt.% dihydrate seeds added. Data were recorded in transmission mode using a position sensitive detector and synchrotron X-ray radiation of optimised intensity (wavelength 1.4 A). The dissolution of the hemihydrate and the formation of the dihydrate were both monitored. Varying the water/solid weight ratio (w/s) from 0.50 to 1.50 did not affect the reaction rate significantly. Addition of 0.50 wt.% potassium sulfate to the water accelerates the reaction and 0.25 wt.% citric acid monohydrate causes retardation; times for complete reaction: 17 and 42 min, respectively, compared to 28-32 min without additive (w/s = 1.00). A comparison of the reaction curves shows (i) that hemihydrate dissolves and dihydrate precipitates at the same rate, and (ii) that preferred orientation effects are absent in the diffraction experiments.
Dissolution of CaSO4 dot 1/2H2O and precipitation of CaSO4 dot 2H2O - A kinetic study by synchrotron X-ray powder diffraction
Time-resolved X-ray powder diffraction has been performed on hydrating samples of calcium sulfate hemihydrate with 0.50 wt.% dihydrate seeds added. Data were recorded in transmission mode using a position sensitive detector and synchrotron X-ray radiation of optimised intensity (wavelength 1.4 A). The dissolution of the hemihydrate and the formation of the dihydrate were both monitored. Varying the water/solid weight ratio (w/s) from 0.50 to 1.50 did not affect the reaction rate significantly. Addition of 0.50 wt.% potassium sulfate to the water accelerates the reaction and 0.25 wt.% citric acid monohydrate causes retardation; times for complete reaction: 17 and 42 min, respectively, compared to 28-32 min without additive (w/s = 1.00). A comparison of the reaction curves shows (i) that hemihydrate dissolves and dihydrate precipitates at the same rate, and (ii) that preferred orientation effects are absent in the diffraction experiments.
Dissolution of CaSO4 dot 1/2H2O and precipitation of CaSO4 dot 2H2O - A kinetic study by synchrotron X-ray powder diffraction
Solberg, C. (Autor:in) / Hansen, S. (Autor:in)
Cement and Concrete Research ; 31 ; 641-646
2001
6 Seiten, 12 Quellen
Aufsatz (Zeitschrift)
Englisch
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