Changes in crystal structure of ettringite on dehydration. 2

Inference of the phase-to-mechanical property link via coupled X-ray spectrometry and indentation analysis: Application to cement-based materials

“…3CA SH 12 incorporating ≈14% of calcium and ≈7% of aluminum [20], or partially dehydrated ettringite. In its natural state, ettringite incorporates ≈32 molecules of H 2 O in its structure, which results in ≈10% atomic of Ca, ≈3% Al and ≈5% S. However, its crystal structure collapses due to gradual loss of water [33,[50][51][52] when it is exposed to severe dehydration caused by the combined action of vacuum-oven drying (see Fig. 2), the high vacuum of the electron microprobe and possibly heating by the electron beam.…”

The evolution of structural changes in ettringite during thermal decomposition

“…The near halving of the c-axis was attributed to an increase in symmetry concomitant with the dehydration process. Skoblinskaya and Krasilnikov [6,7] studied the dehydration isotherms of ettringite, using X-ray diffraction, crystal optical, and scanning electron microscopy (SEM) techniques, by varying the partial pressure of water vapor to which a synthetic ettringite sample was exposed. Based upon the structural work of Moore and Taylor [8] with the results of their own work, Skoblinskaya and Krasilnikov suggested that ettringite contained four distinct types of water and that the dehydration process followed an orderly, sequential removal of water from these sites.…”

Effect of pressure on the crystal structure of ettringite

“…The thermal dehydration of ettringite has been studied [11,12,13,14] with some disagreement over the exact order of hydroxyl and free water leaving the crystal but general agreement over a large water loss at 110 o C followed by amorphization of the sample after the loss of 20 water units.…”