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XRD analysis of phase development and peak broadening during the production of AAC
Author(s) -
Schreiner Juergen,
Jansen Daniel,
Ectors Dominique,
Volkmann Stephan
Publication year - 2018
Publication title -
ce/papers
Language(s) - English
Resource type - Journals
ISSN - 2509-7075
DOI - 10.1002/cepa.838
Subject(s) - portlandite , tobermorite , ettringite , materials science , phase (matter) , anisotropy , mineralogy , thermodynamics , chemical engineering , composite material , cement , portland cement , chemistry , physics , organic chemistry , quantum mechanics , engineering
Abstract The production process of autoclaved aerated concrete (AAC) is driven by the transformation of mineral phases. During green cake step, strength is developed by the formation of hydrate phases such as ettringite and in larger quantity portlandite. In respective XRD plots, portlandite often shows anisotropic peak broadening due to anisotropic domain morphology. A new implementation in Rietveld refinement allows to refine the peak broadening calculating anisotropic domain sizes. An appropriate model is used to approximate the domains of portlandite. In this way, it is possible to track the mechanism of portlandite growth during hydration and the quantification of phase development during the green cake hydration is performed more precisely. In autoclaved samples, the main phase is tobermorite, which shows anisotropic peak broadening as well. The application of the described approach in a similar way to portlandite enables an advanced refinement. To approximate the domains of tobermorite a triaxial cylinder model is used, so that tobermorite is characterized more accurately. In addition, this method allows to investigate the influence of variations in the chemical composition of raw materials on domain morphology of tobermorite, as exchanged ions like Al 3+ make a significant impact. Consequently, a new possibility to analyze the link between mechanical and thermal properties and phase characteristics is given.