Calcium Sulfoaluminate Sodalite (Ca 4 Al 6 O 12 SO 4 ) Crystal Structure Evaluation and Bulk Modulus Determination

Craig W. Hargis, Juhyuk Moon, Barbara Lothenbach, Frank Winnefeld, Hans-Rudolf Wenk, Paulo J. M. Monteiro

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39 Scopus citations


The predominant phase of calcium sulfoaluminate cement, Ca 4(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(Al 6O12)SO4 is presented. Rietveld refinements showed the orthorhombic crystal structure to best match the observed peak intensities and positions for pure Ca4(Al6O 12)SO4. The compressibility of Ca4(Al 6O12)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(Al6O 12)SO4 is higher than other sodalites with monovalent cage ions, such as Na8(AlSiO4)6Cl2 or Na8(AlSiO4)6(OH)2·H 2O. 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. © 2013 The American Ceramic Society.
Original languageEnglish (US)
Pages (from-to)892-898
Number of pages7
JournalJournal of the American Ceramic Society
Issue number3
StatePublished - Dec 12 2013
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-l1-004021
Acknowledgements: Supported in part by Award No. KUS-l1-004021, made by King Abdullah University of Science and Technology (KAUST). C.W. Hargis was supported by the Berkeley Fellowship for Graduate Study and the Carlson-Polivka Fellowship. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. C.W. Hargis thanks Dr. Rae Taylor and Prof. Wulf Depmeier for their insightful discussions.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.


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