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Title: Improved evidence for the existence of an intermediate phase during hydration of tricalcium silicate

Tricalcium silicate (Ca{sub 3}SiO{sub 5}) with a very small particle size of approximately 50 nm has been prepared and hydrated for a very short time (5 min) by two different modes in a paste experiment, using a water/solid-ratio of 1.20, and by hydration as a suspension employing a water/solid-ratio of 4000. A phase containing uncondensed silicate monomers close to hydrogen atoms (either hydroxyl groups or water molecules) was formed in both experiments. This phase is distinct from anhydrous tricalcium silicate and from the calcium-silicate-hydrate (C-S-H) phase, commonly identified as the hydration product of tricalcium silicate. In the paste experiment, approximately 79% of silicon atoms were present in the hydrated phase containing silicate monomers as determined from {sup 29}Sileft brace{sup 1}Hright brace CP/MAS NMR. This result is used to show that the hydrated silicate monomers are part of a separate phase and that they cannot be attributed to a hydroxylated surface of tricalcium silicate after contact with water. The phase containing hydrated silicate monomers is metastable with respect to the C-S-H phase since it transforms into the latter in a half saturated calcium hydroxide solution. These data is used to emphasize that the hydration of tricalcium silicate proceeds in two consecutivemore » steps. In the first reaction, an intermediate phase containing hydrated silicate monomers is formed which is subsequently transformed into C-S-H as the final hydration product in the second step. The introduction of an intermediate phase in calculations of the early hydration of tricalcium silicate can explain the presence of the induction period. It is shown that heterogeneous nucleation on appropriate crystal surfaces is able to reduce the length of the induction period and thus to accelerate the reaction of tricalcium silicate with water.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3]
  1. Institute for Building Materials Science, Bauhaus University Weimar, 99423 Weimar (Germany)
  2. Ecole des Mines de Douai, Civil and Environmental Engineering Department, 941 rue Charles Bourseul, BP 10838, 59508 Doua cedexi (France)
  3. Instrument Center for Solid-State NMR Spectroscopy and Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, Aarhus University DK-8000 Aarhus C (Denmark)
Publication Date:
OSTI Identifier:
21344767
Resource Type:
Journal Article
Resource Relation:
Journal Name: Cement and Concrete Research; Journal Volume: 40; Journal Issue: 6; Other Information: DOI: 10.1016/j.cemconres.2010.02.007; PII: S0008-8846(10)00044-X; Copyright (c) 2010 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CALCIUM HYDROXIDES; CALCIUM SILICATES; HYDRATES; HYDRATION; MONOMERS; NUCLEAR MAGNETIC RESONANCE; PARTICLE SIZE; SURFACES; SUSPENSIONS; WATER ALKALINE EARTH METAL COMPOUNDS; CALCIUM COMPOUNDS; DISPERSIONS; HYDROGEN COMPOUNDS; HYDROXIDES; MAGNETIC RESONANCE; OXYGEN COMPOUNDS; RESONANCE; SILICATES; SILICON COMPOUNDS; SIZE; SOLVATION