A comparative structural study of wet and dried ettringite

Journal Article · Mon Mar 15 00:00:00 EDT 2010 · Cement and Concrete Research

DOI:https://doi.org/10.1016/j.cemconres.2009.11.002· OSTI ID:21344747

Renaudin, G ^[1]; Filinchuk, Y ^[2]; Neubauer, J ^[3]; Goetz-Neunhoeffer, F ^[3]

---

1. Clermont Universite, ENSCCF, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France)
2. Swiss-Norwegian Beam Lines at ESRF, 6 rue Jules Horowitz, BP 220, 38043 Grenoble (France)
3. University of Erlangen, GeoZentrum Nordbayern, Mineralogy, Schlossgarten 5 a, 91054 Erlangen (Germany)

Two different techniques were used to compare structural characteristics of 'wet' ettringite (stored in the synthesis mother liquid) and 'dried' ettringite (dried to 35% relative humidity over saturated CaCl{sub 2} solution). Lattice parameters and the water content in the channel region of the structure (site occupancy factor of the water molecule not bonded to cations) as well as microstructure parameters (size and strain) were determined from a Rietveld refinement on synchrotron powder diffraction data. Local environment of sulphate anions and of the hydrogen bonding network was characterized by Raman spectroscopy. Both techniques led to the same conclusion: the 'wet' ettringite sample immersed in the mother solution from the synthesis presents similar structural features as ettringite dried to 35% relative humidity. An increase of the a lattice parameter combined with a decrease of the c lattice parameter occurs on drying. The amount of structural water, the point symmetry of sulphate and the hydrogen bond network are unchanged when passing from the wet to the dried ettringite powder. Ettringite does not form a high-hydrate polymorph in equilibrium with alkaline solution, in contrast to the AFm phases that lose water molecules on drying. According to these results we conclude that ettringite precipitated in aqueous solution at the early hydration stages is of the same chemical composition as ettringite present in the hardening concrete.

• OSTI ID: 21344747
• Journal Information: Cement and Concrete Research, Vol. 40, Issue 3; Other Information: DOI: 10.1016/j.cemconres.2009.11.002; PII: S0008-8846(09)00317-2; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0008-8846
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AQUEOUS SOLUTIONS
CALCIUM CHLORIDES
CHEMICAL COMPOSITION
CONCRETES
CRYSTAL STRUCTURE
DRYING
HARDENING
HUMIDITY
HYDRATES
HYDRATION
LATTICE PARAMETERS
LIQUIDS
MICROSTRUCTURE
RAMAN SPECTROSCOPY
STRAINS
SULFATES
SYNTHESIS
WATER
X-RAY DIFFRACTION
ALKALINE EARTH METAL COMPOUNDS
BUILDING MATERIALS
CALCIUM COMPOUNDS
CALCIUM HALIDES
CHLORIDES
CHLORINE COMPOUNDS
COHERENT SCATTERING
DIFFRACTION
DISPERSIONS
FLUIDS
HALIDES
HALOGEN COMPOUNDS
HOMOGENEOUS MIXTURES
HYDROGEN COMPOUNDS
LASER SPECTROSCOPY
MATERIALS
MIXTURES
MOISTURE
OXYGEN COMPOUNDS
SCATTERING
SOLUTIONS
SOLVATION
SPECTROSCOPY
SULFUR COMPOUNDS