The solubility of selenate-AFt (3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}3CaSeO{sub 4}{center_dot}37.5H{sub 2}O) and selenate-AFm (3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}CaSeO{sub 4}{center_dot}xH{sub 2}O)
Journal Article
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· Cement and Concrete Research
The Se(VI)-analogues of ettringite and monosulfate, selenate-AFt (3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}3CaSeO{sub 4}{center_dot}37.5H{sub 2}O), and selenate-AFm (3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}CaSeO{sub 4}{center_dot}xH{sub 2}O) were synthesised and characterised by bulk chemical analysis and X-ray diffraction. Their solubility products were determined from a series of batch and resuspension experiments conducted at 25 deg. C. For selenate-AFt suspensions, the pH varied between 11.37 and 11.61, and a solubility product, log K{sub so}=61.29{+-}0.60 (I=0 M), was determined for the reaction 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}3CaSeO{sub 4}{center_dot}37.5H{sub 2}O+12 H{sup +} implies 6Ca{sup 2+}+2Al{sup 3+}+3SeO{sub 4}{sup 2-}+43.5H{sub 2}O. Selenate-AFm synthesis resulted in the uptake of Na, which was leached during equilibration and resuspension. For the pH range of 11.75 to 11.90, a solubility product, log K{sub so}=73.40{+-}0.22 (I=0 M), was determined for the reaction 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}CaSeO{sub 4}{center_dot}xH{sub 2}O+12 H{sup +} implies 4Ca{sup 2+}+2Al{sup 3+}+SeO{sub 4}{sup 2-}+(x+6)H{sub 2}O. Thermodynamic modelling suggested that both selenate-AFt and selenate-AFm are stable in the cementitious matrix; and that in a cement limited in sulfate, selenate concentration may be limited by selenate-AFm to below the millimolar range above pH 12.
- OSTI ID:
- 20658277
- Journal Information:
- Cement and Concrete Research, Journal Name: Cement and Concrete Research Journal Issue: 11 Vol. 33; ISSN 0008-8846; ISSN CCNRAI
- Country of Publication:
- United States
- Language:
- English
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