Calcium Sulfoaluminate Sodalite (Ca4Al6O12SO4) Crystal Structure Evaluation and Bulk Modulus Determination

The predominant phase of calcium sulfoaluminate cement, Ca4(Al6O12)SO4, was investigated using high‐pressure synchrotron X‐ray diffraction from ambient pressure to 4.75 GPa. A critical review of the crystal structure of Ca4(Al6O12)SO4 is presented. Rietveld refinements showed the orthorhombic crysta...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 2014-03, Vol.97 (3), p.892-898
Main Authors: Hargis, Craig W., Moon, Juhyuk, Lothenbach, Barbara, Winnefeld, Frank, Wenk, Hans-Rudolf, Monteiro, Paulo J. M.
Format: Article
Language:English
Subjects:
Ceramics
Crystal structure
Diffraction
Ions
Phase transitions
Pressure
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Summary:The predominant phase of calcium sulfoaluminate cement, Ca4(Al6O12)SO4, was investigated using high‐pressure synchrotron X‐ray diffraction from ambient pressure to 4.75 GPa. A critical review of the crystal structure of Ca4(Al6O12)SO4 is presented. Rietveld refinements showed the orthorhombic crystal structure to best match the observed peak intensities and positions for pure Ca4(Al6O12)SO4. The compressibility of Ca4(Al6O12)SO4 was studied using cubic, orthorhombic, and tetragonal crystal structures due to the lack of consensus on the actual space group, and all three models provided similar results of 69(6) GPa. With its divalent cage ions, the bulk modulus of Ca4(Al6O12)SO4 is higher than other sodalites with monovalent cage ions, such as Na8(AlSiO4)6Cl2 or Na8(AlSiO4)6(OH)2·H2O. Likewise, comparing this study to previous ones shows the lattice compressibility of aluminate sodalites decreases with increasing size of the caged ions. Ca4(Al6O12)SO4 is more compressible than other cement clinker phases such as tricalcium aluminate and less compressible than hydrated cement phases such as ettringite and hemicarboaluminate.
ISSN:0002-7820
1551-2916
DOI:10.1111/jace.12700