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Modelling of microstructure of Portland cement: fly ash binders based on calorimetric and thermogravimetric experiments

Nele De Belie UGent, Gert Baert and Geert De Schutter UGent (2011) Chemistry of Cement, XIII ICCC International congress, Proceedings. p.1-7
abstract
presence of fly ash. The kinetics of the reactions have been analysed by fitting generally known models such as e.g. the Avrami and Jander equations to isothermal heat measurements on fly ash – cement pastes. The pozzolanic reaction of fly ash is described with equations in which pozzolanic CSH and strätlingite are formed. Pastes of various cement-fly ash combinations have also been subjected to thermogravimetric analysis at curing ages varying between 3 hours and 2 years. The amount of calcium hydroxide and chemically bound water present at the test age have been analysed. A decrease in calcium hydroxide content with time is an indication for the on-going pozzolanic reaction of fly ash. The fly ash reaction degree was also measured by means of selective dissolution in a water-methanol-picric acid solution. It can be concluded that the amount of calcium hydroxide consumed by one gram reacted fly ash varies with time. A maximum of 0.6 to 0.7 gram calcium hydroxide per gram reacted fly ash was obtained after a curing period of three to six months. The amount of chemically bound water follows from the thermogravimetric experiments. Upon its reaction with cement and fly ash, water receives a smaller specific volume resulting in a chemical shrinkage of the paste. The obtained values for water retention are not only in agreement with the experimental findings of Powers, but also confirm what stoichiometrically could be expected. Also the amount of chemically bound water per gram reacted fly ash has been determined for the fly ash equations in which pozzolanic CSH and strätlingite are formed. From the calculated amount of retained water, chemical shrinkage and volume portion of each reaction product and unreacted particles, the microstructure can be quantified. The calculated volume fractions are compared with predictions by the 3-dimensional NIST model. A good correlation between both can be concluded for the CSH phase and the dissolution of alite and belite.
Please use this url to cite or link to this publication:
author
organization
year
type
conference
publication status
published
subject
keyword
thermogravimetry, selective dissolution, microstructure, Fly ash, hydration model
in
Chemistry of Cement, XIII ICCC International congress, Proceedings
pages
1 - 7
publisher
Ghent University, Department of Structural engineering
place of publication
Ghent, Belgium
conference name
13th ICCC International congress on the Chemistry of Cement
conference location
Madrid, Spain
conference start
2011-07-03
conference end
2011-07-08
language
English
UGent publication?
yes
classification
C1
copyright statement
I have transferred the copyright for this publication to the publisher
id
2920163
handle
http://hdl.handle.net/1854/LU-2920163
date created
2012-06-26 13:30:43
date last changed
2017-01-02 09:53:24
@inproceedings{2920163,
  abstract     = {presence of fly ash. The kinetics of the reactions have been analysed by fitting generally known models such as e.g. the Avrami and Jander equations to isothermal heat measurements on fly ash -- cement pastes. The pozzolanic reaction of fly ash is described with equations in which pozzolanic CSH and str{\"a}tlingite are formed. Pastes of various cement-fly ash combinations have also been subjected to thermogravimetric analysis at curing ages varying between 3 hours and 2 years. The amount of calcium hydroxide and chemically bound water present at the test age have been analysed. A decrease in calcium hydroxide content with time is an indication for the on-going pozzolanic reaction of fly ash. The fly ash reaction degree was also measured by means of selective dissolution in a water-methanol-picric acid solution. It can be concluded that the amount of calcium hydroxide consumed by one gram reacted fly ash varies with time. A maximum of 0.6 to 0.7 gram calcium hydroxide per gram reacted fly ash was obtained after a curing period of three to six months. The amount of chemically bound water follows from the thermogravimetric experiments. Upon its reaction with cement and fly ash, water receives a smaller specific volume resulting in a chemical shrinkage of the paste. The obtained values for water retention are not only in agreement with the experimental findings of Powers, but also confirm what stoichiometrically could be expected. Also the amount of chemically bound water per gram reacted fly ash has been determined for the fly ash equations in which pozzolanic CSH and str{\"a}tlingite are formed. From the calculated amount of retained water, chemical shrinkage and volume portion of each reaction product and unreacted particles, the microstructure can be quantified. The calculated volume fractions are compared with predictions by the 3-dimensional NIST model. A good correlation between both can be concluded for the CSH phase and the dissolution of alite and belite.},
  author       = {De Belie, Nele and Baert, Gert and De Schutter, Geert},
  booktitle    = {Chemistry of Cement, XIII ICCC International congress, Proceedings},
  keyword      = {thermogravimetry,selective dissolution,microstructure,Fly ash,hydration model},
  language     = {eng},
  location     = {Madrid, Spain},
  pages        = {1--7},
  publisher    = {Ghent University, Department of Structural engineering},
  title        = {Modelling of microstructure of Portland cement: fly ash binders based on calorimetric and thermogravimetric experiments},
  year         = {2011},
}

Chicago
De Belie, Nele, Gert Baert, and Geert De Schutter. 2011. “Modelling of Microstructure of Portland Cement: Fly Ash Binders Based on Calorimetric and Thermogravimetric Experiments.” In Chemistry of Cement, XIII ICCC International Congress, Proceedings, 1–7. Ghent, Belgium: Ghent University, Department of Structural engineering.
APA
De Belie, Nele, Baert, G., & De Schutter, G. (2011). Modelling of microstructure of Portland cement: fly ash binders based on calorimetric and thermogravimetric experiments. Chemistry of Cement, XIII ICCC International congress, Proceedings (pp. 1–7). Presented at the 13th ICCC International congress on the Chemistry of Cement, Ghent, Belgium: Ghent University, Department of Structural engineering.
Vancouver
1.
De Belie N, Baert G, De Schutter G. Modelling of microstructure of Portland cement: fly ash binders based on calorimetric and thermogravimetric experiments. Chemistry of Cement, XIII ICCC International congress, Proceedings. Ghent, Belgium: Ghent University, Department of Structural engineering; 2011. p. 1–7.
MLA
De Belie, Nele, Gert Baert, and Geert De Schutter. “Modelling of Microstructure of Portland Cement: Fly Ash Binders Based on Calorimetric and Thermogravimetric Experiments.” Chemistry of Cement, XIII ICCC International Congress, Proceedings. Ghent, Belgium: Ghent University, Department of Structural engineering, 2011. 1–7. Print.