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

Abstract

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

Citation Formats

Bellmann, Frank, E-mail: frank.bellmann@uni-weimar.d, Damidot, Denis, Moeser, Bernd, and Skibsted, Jorgen. Improved evidence for the existence of an intermediate phase during hydration of tricalcium silicate. United States: N. p., 2010. Web. doi:10.1016/j.cemconres.2010.02.007.
Bellmann, Frank, E-mail: frank.bellmann@uni-weimar.d, Damidot, Denis, Moeser, Bernd, & Skibsted, Jorgen. Improved evidence for the existence of an intermediate phase during hydration of tricalcium silicate. United States. doi:10.1016/j.cemconres.2010.02.007.
Bellmann, Frank, E-mail: frank.bellmann@uni-weimar.d, Damidot, Denis, Moeser, Bernd, and Skibsted, Jorgen. 2010. "Improved evidence for the existence of an intermediate phase during hydration of tricalcium silicate". United States. doi:10.1016/j.cemconres.2010.02.007.
@article{osti_21344767,
title = {Improved evidence for the existence of an intermediate phase during hydration of tricalcium silicate},
author = {Bellmann, Frank, E-mail: frank.bellmann@uni-weimar.d and Damidot, Denis and Moeser, Bernd and Skibsted, Jorgen},
abstractNote = {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 consecutive 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.},
doi = {10.1016/j.cemconres.2010.02.007},
journal = {Cement and Concrete Research},
number = 6,
volume = 40,
place = {United States},
year = 2010,
month = 6
}
  • New information on the water bonding during the first 36 h of hydration of tricalcium silicate was obtained using the high neutron flux at the sample position of the time-of-flight spectrometer (TOFTOF), FRM II in Garching, Germany, together with {sup 29}Si NMR and X-ray diffraction measurements. A rapid increase in the amount of constrained water was observed at the beginning of the induction period. This is attributed to the formation of an early C-S-H with a large specific surface area (around 800 m{sup 2}/g). During subsequent hydration, the amount of constrained water, as given by the total surface area ofmore » the hydration products, is controlled by (a) the formation of new metastable early C-S-H which increases total surface area and (b) polymerisation processes which reduce total surface area. The relative contribution of these processes varies during hydration.« less
  • Quasielastic neutron scattering (QNS) measurements of the hydration kinetics of tricalcium silicate (C{sub 3}S) have been made with 60 {micro}eV energy resolution at a momentum transfer q = 1 {angstrom}{sup {minus}1}. Monitoring the fraction of neutrons elastically scattered from C{sub 3}S paste specimens follows the progress of the C{sub 3}S hydration reactions. Three different water/cement ratios (w/c = 0.3, 0.5, and 0.7) were studied in this experiment. Analysis of the rate of reaction over the first approximately 15 h was by an Avrami model. After this time, the rate of hydration no longer follows nucleation and growth kinetics but entersmore » a diffusion controlled regime. At this point, the rate of hydration depends strongly on the w/c, with more reaction at higher w/c ratios. A shrinking core model was used to analyze the diffusion-limited portion of the reaction at later times. The values of the apparent diffusion constant obtained from these data indicate a log-linear relationship between the diffusion constants and the w/c ratio.« less
  • The hydration of tricalcium silicate (C{sub 3}S) is accelerated by pressure. However, the extent to which temperature and/or cement additives modify this effect is largely unknown. Time-resolved synchrotron powder diffraction has been used to study cement hydration as a function of pressure at different temperatures in the absence of additives, and at selected temperatures in the presence of retarding agents. The magnitudes of the apparent activation volumes for C{sub 3}S hydration increased with the addition of the retarders sucrose, maltodextrin, aminotri(methylenephosphonic acid) and an AMPS copolymer. Pressure was found to retard the formation of Jaffeite relative to the degree ofmore » C{sub 3}S hydration in high temperature experiments. For one cement slurry studied without additives, the apparent activation volume for C{sub 3}S hydration remained close to {approx} -28 cm{sup 3} mol{sup -1} over the range 25 to 60 C. For another slurry, there were possible signs of a decrease in magnitude at the lowest temperature examined.« less
  • Tmore » he effect of calcium chloride (CaCl 2 ) on tricalcium silicate (C 3 S) hydration was investigated by scanning transmission X-ray microscopy (SXM) with Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra and 29 Si MAS NMR. SXM is demonstrated to be a powerful tool for studying the chemical composition of a cement-based hydration system. he Ca L 3,2 -edge NEXAFS spectra obtained by examining C 3 S hydration in the presence of CaCl 2 showed that this accelerator does not change the coordination of calcium in the calcium silicate hydrate (C-S-H), which is the primary hydration product. O K-edge NEXAFS is also very useful in distinguishing the chemical components in hydrated C 3 S. Based on the Ca L 3,2 -edge spectra and chemical component mapping, we concluded that CaCl 2 prefers to coexist with unhydrated C 3 S instead of C-S-H. In Si K-edge NEXAFS analysis, CaCl 2 increases the degree of silicate polymerization of C-S-H in agreement with the 29 Si CP/MAS NMR results, which show that the presence of CaCl 2 in hydrated C 3 S considerably accelerates the formation of middle groups ( Q 2 ) and branch sites ( Q 3 ) in the silicate chains of C-S-H gel at 1-day hydration.« less
  • Based on conceptual models for the stages in the hydration of tricalcium silicate, a mathematical model was developed. The separate resistances in the mathematical model correspond to the phenomenological stages of the conceptual model. Comparison of model output with available hydration data gave a reasonable fit between the model and the data. 7 references, 2 figures.