Structural changes during thermal dehydration of ettringite

Autor:	Yukie Shimada, J. F. Young
Rok vydání:	2001
Předmět:	Ettringite Coordination number chemistry.chemical_element Mineralogy Building and Construction Crystal structure Calcium medicine.disease Thermogravimetry chemistry.chemical_compound chemistry Chemical engineering Aluminium X-ray crystallography medicine General Materials Science Dehydration
Zdroj:	Advances in Cement Research. 13:77-81
ISSN:	1751-7605 0951-7197
DOI:	10.1680/adcr.2001.13.2.77
Popis:	Changes in crystal structure of ettringite on dehydration in normal atmosphere have been re-examined by means of thermogravimetry, X-ray diffraction, and 27Al nuclear magnetic resonance spectroscopy. Synthetic ettringite crystals were heated at various temperatures up to 200°C for durations of up to 7 h. The ettringite structure maintains some long-range order until the coordination number of calcium changes to 5 by dehydration of twelve water molecules from channels and columns with heat treatment at 70°C. When the coordination number of calcium decreases to 5, the short-range order of the structure is disrupted and ettringite becomes X-ray-amorophous. Subsequently, the rest of the water molecules in the columns and bridging OH groups in calcium polyhedra are removed, essentially destroying the framework of the columns. This is accompanied by changes in the coordination number of aluminium from 6 to 4.
Databáze:	OpenAIRE
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