Bulk modulus of basic sodalite, Na8[AlSiO4] 6(OH)2•2H2O, a possible zeolitic precursor in coal-fly-ash-based geopolymers

Jae Eun Oh, Juhyuk Moon, Mauricio Mancio, Simon M. Clark, Paulo J M Monteiro

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23 Citations (Scopus)


Synthetic basic sodalite, Na8[AlSiO4] 6(OH)2•2H2O, cubic, P43n, (also known as hydroxysodalite hydrate) was prepared by the alkaline activation of amorphous aluminosilicate glass, obtained from the phase separation of Class F fly ash. The sample was subjected to a process similar to geopolymerization, using high concentrations of a NaOH solution at 90 °C for 24 hours. Basic sodalite was chosen as a representative analogue of the zeolite precursor existing in Na-based Class F fly ash geopolymers. To determine its bulk modulus, high-pressure synchrotron X-ray powder diffraction was applied using a diamond anvil cell (DAC) up to a pressure of 4.5 GPa. A curve-fit with a truncated third-order Birch-Murnaghan equation of state with a fixed K'o = 4 to pressure-normalized volume data yielded the isothermal bulk modulus, K o = 43 ± 4 GPa, indicating that basic sodalite is more compressible than sodalite, possibly due to a difference in interactions between the framework host and the guest molecules.

Original languageEnglish
Pages (from-to)107-112
Number of pages6
JournalCement and Concrete Research
Issue number1
Publication statusPublished - Jan 2011
Externally publishedYes


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