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Hydration of calcium aluminates at 60°C – Development paths of C 2 AH x in dependence on the content of free water
Author(s) -
Hueller Florian,
Neubauer Juergen,
Kaessner Stefan,
GoetzNeunhoeffer Friedlinde
Publication year - 2019
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.16314
Subject(s) - dehydration , aluminate , hydrate , chemistry , calcium , precipitation , evaporation , phase (matter) , mineralogy , cement , materials science , metallurgy , organic chemistry , thermodynamics , biochemistry , physics , meteorology
Abstract The influence of water loss during the hydration of calcium aluminates on the phase development is investigated at 60°C. This is relevant for applications in which calcium aluminate cement ( CAC ) based formulations are exposed to quick drying during hydration. The presented results provide new insights into the well‐known conversion processes occurring in CAC pastes. Using in situ XRD two different routes of the development of initially formed C 2 AH 8 are determined: (a) transformation to C 3 AH 6 + AH 3 in the presence of sufficient free water and (b) dehydration to C 2 AH 5 at a lack of free water. Moreover, the influence of precuring of the pastes at 23°C before heating to 60°C is investigated. The increasing loss of free water with increasing precuring time resulting from both, precipitation of hydrate phases and evaporation, causes incomplete hydration of CA or CA 2 as well as dehydration of C 2 AH 8 instead of conversion into C 3 AH 6 . Comparative investigations of sealed samples always revealed complete hydration of CA and CA 2 as well as complete conversion of C 2 AH 8 .