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Title: Fe-containing phases in hydrated cements

In this study synchrotron X-ray absorption spectroscopy (XAS) has been applied, an element specific technique which allows Fe-containing phases to be identified in the complex mineral mixture of hydrated cements. Several Fe species contributed to the overall Fe K-edge spectra recorded on the cement samples. In the early stage of cement hydration ferrite was the dominant Fe-containing mineral. Ferrihydrite was detected during the first hours of the hydration process. After 1 day the formation of Al- and Fe-siliceous hydrogarnet was observed, while the amount of ferrihydrite decreased. The latter finding agrees with thermodynamic modeling, which predicts the formation of Fe-siliceous hydrogarnet in Portland cement systems. The presence of Al- and Fe-containing siliceous hydrogarnet was further substantiated in the residue of hydrated cement by performing a selective dissolution procedure. - Highlights: • Fe bound to ferrihydrite at early age hydration • Fe found to be stable in siliceous hydrogarnet at longer term age hydration • Fe-containing AFt and AFm phases are less stable than siliceous hydrogarnet. • The study demonstrates EXAFS used to identify amorphous or poorly crystalline phases.
Authors:
 [1] ;  [2] ;  [1] ;  [2] ;  [3]
  1. Empa, Laboratory for Concrete and Construction Chemistry, Überlandstrasse 129, 8600 Dübendorf (Switzerland)
  2. Paul Scherrer Institute, Laboratory for Waste Management, 5232 Villigen PSI (Switzerland)
  3. Ecole Polytechnique Federal de Lausanne (EPFL), Laboratory for Construction Materials, 1015 Lausanne (Switzerland)
Publication Date:
OSTI Identifier:
22323132
Resource Type:
Journal Article
Resource Relation:
Journal Name: Cement and Concrete Research; Journal Volume: 58; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTROSCOPY; ATOMIC FORCE MICROSCOPY; DISSOLUTION; FERRITE; FERRITES; FINE STRUCTURE; HYDRATION; MINERALS; MIXTURES; PORTLAND CEMENT; SPECTRA; X-RAY SPECTROSCOPY