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Title: Structural changes in C–S–H gel during dissolution: Small-angle neutron scattering and Si-NMR characterization

Flow-through experiments were conducted to study the calcium–silicate–hydrate (C–S–H) gel dissolution kinetics. During C–S–H gel dissolution the initial aqueous Ca/Si ratio decreases to reach the stoichiometric value of the Ca/Si ratio of a tobermorite-like phase (Ca/Si = 0.83). As the Ca/Si ratio decreases, the solid C–S–H dissolution rate increases from (4.5 × 10{sup −} {sup 14} to 6.7 × 10{sup −} {sup 12}) mol m{sup −} {sup 2} s{sup −} {sup 1}. The changes in the microstructure of the dissolving C–S–H gel were characterized by small-angle neutron scattering (SANS) and {sup 29}Si magic-angle-spinning nuclear magnetic resonance ({sup 29}Si-MAS NMR). The SANS data were fitted using a fractal model. The SANS specific surface area tends to increase with time and the obtained fit parameters reflect the changes in the nanostructure of the dissolving solid C–S–H within the gel. The {sup 29}Si MAS NMR analyses show that with dissolution the solid C–S–H structure tends to a more ordered tobermorite structure, in agreement with the Ca/Si ratio evolution.
Authors:
 [1] ;  [2] ;  [3] ; ;  [1] ;  [2]
  1. Institute of Environmental Assessment and Water Research (IDAEA), Barcelona 08034, Catalonia (Spain)
  2. National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899 (United States)
  3. (France)
Publication Date:
OSTI Identifier:
22475508
Resource Type:
Journal Article
Resource Relation:
Journal Name: Cement and Concrete Research; Journal Volume: 72; Other Information: Copyright (c) 2015 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; CALCIUM; CALCIUM SILICATES; CARBON NITRIDES; CARBON SULFIDES; CEMENTS; DISSOLUTION; FRACTALS; GELS; HYDRATES; MICROSTRUCTURE; NANOSTRUCTURES; NEUTRON DIFFRACTION; NMR SPECTRA; NUCLEAR MAGNETIC RESONANCE; SILICON 29; SMALL ANGLE SCATTERING; X-RAY DIFFRACTION