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Influence of low-pressure treatment on the morphological and compositional stability of microscopic ettringite
Publikationstyp
Journal Article
Date Issued
2021-05-21
Sprache
English
Author(s)
Lübkemann, Franziska
von Bronk, Tabea
Cotardo, Dario
Lohaus, Ludger
Haist, Michael
Bigall, Nadja C.
Journal
Volume
14
Issue
11
Article Number
2720
Citation
Materials 14 (11): 2720 (2021)
Publisher DOI
Scopus ID
Publisher
MDPI AG
The impact of low-pressure treatment on the crystal structure, morphology, and chemical composition of ettringite, due to their major importance with respect to processability (i.a., drying conditions) and to the analysis of ettringite-containing samples, is examined utilizing X-ray diffraction, thermogravimetric analysis, Raman spectroscopy, and environmental scanning electron microscopy. Synthetic ettringite was treated for various durations (5 min up to 72 h) and at two different levels of low-pressure (4.0 mbar and 60 µbar). Evaluation showed a correlation between the procedural parameters (time and pressure), the chemical composition, and the morphology of ettringite. The experiments reveal that, when exposed to 4 mbar pressure, nearly no changes occur in the ettringite’s morphology, whereas the crystals undergo swelling and slight deformations at very low pressures (60 µbar and 35.3 nbar), which is attributed to the loss of bound water and the partial transformation from ettringite to quicklime, anhydrite, and calcium aluminate. Furthermore, the strongly dehydrated ettringite shows the same morphology.
Subjects
chemical composition
ettringite
low-pressure
morphology
Pawley fit
DDC Class
540: Chemistry