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Determination of the degree of reaction of fly ash in blended cement pastes

Nele De Belie UGent, Karen Scrivener, B Lothenbach, Elke Gruyaert, J Skibsted, Ruben Snellings, A Vollpracht and Y Villagran (2015) 14th International Congress on the Chemistry of Cement, Proceedings. p.1-12
abstract
This paper gives a review over methods to determine the degree of reaction for supplementary cementitious materials (SCMs) with focus on Portland cement - fly ash blends only and summarizes and highlights the most important findings which are detailed in a parallel paper published in Materials and Structures. Determination of the extent of the reaction of SCMs in mixtures is complicated for several reasons: (1) the physical presence of SCMs affects the rate and extent of the reaction of the ground clinker component – the so called “filler effect”; (2) SCMs are usually amorphous with complex and varied mineralogy which make them difficult to quantify by many classical techniques such as X-ray diffraction; (3) the rate of reaction of SCMs in a cement blend may be quite different from its rate of reaction in systems containing simply alkali or lime. From this review it is clear that measuring the degree of reaction of SCMs remains challenging. Nevertheless progress has been made in recent years to offer alternatives to the traditional selective dissolution methods. Unfortunately some of these – image analysis and EDS mapping in the scanning electron microscope, and NMR - depend on access to expensive equipment and are time consuming. With regard to fly ashes, NMR seems to be reliable but limited to fly ash with low iron content. New methods with quantitative EDS mapping to segment fly ash particles from the hydrated matrix and to follow the reaction of glass groups of disparate composition separately look very promising, but time consuming. Sources with a high proportion of fine particles will have higher errors due to lower limit of resolution (1-2 μm). Whereas for SCMs which react relatively fast (e.g. slag, calcined clay) the methods based on calorimetry and chemical shrinkage seem promising on a comparative basis, the very low reaction degree of fly ashes before 28 days means that the calorimetry method is not practical. There is a lack of data to assess the usefulness of long term chemical shrinkage measurements. The possibility to quantify the amorphous phase by XRD is promising as this is a widely available and rapid technique which can at the same time give a wealth of additional information on the phases formed. However, the different reaction rates of different glasses in compositionally heterogeneous fly ashes will need to be accounted for and may strongly reduce the accuracy of the profile decomposition method. This paper is the work of working group 2 of the RILEM TC 238-SCM “Hydration and microstructure of concrete with supplementary cementitious materials”.
Please use this url to cite or link to this publication:
author
organization
year
type
conference
publication status
published
subject
keyword
filler effect, quantitative analysis, fly ash, Supplementary cementitious material, reaction degree
in
14th International Congress on the Chemistry of Cement, Proceedings
editor
Caijun Shi and Yan Yao
pages
1 - 12
conference name
14th International Congress on the Chemistry of Cement (ICCC2015)
conference location
Beijing, China
conference start
2015-10-13
conference end
2015-10-16
language
English
UGent publication?
yes
classification
C1
copyright statement
I have retained and own the full copyright for this publication
id
6965192
handle
http://hdl.handle.net/1854/LU-6965192
date created
2015-10-22 11:24:59
date last changed
2016-12-19 15:37:23
@inproceedings{6965192,
  abstract     = {This paper gives a review over methods to determine the degree of reaction for supplementary cementitious materials (SCMs) with focus on Portland cement - fly ash blends only and summarizes and highlights the most important findings which are detailed in a parallel paper published in Materials and Structures.
Determination of the extent of the reaction of SCMs in mixtures is complicated for several reasons: (1) the physical presence of SCMs affects the rate and extent of the reaction of the ground clinker component -- the so called {\textquotedblleft}filler effect{\textquotedblright}; (2) SCMs are usually amorphous with complex and varied mineralogy which make them difficult to quantify by many classical techniques such as X-ray diffraction; (3) the rate of reaction of SCMs in a cement blend may be quite different from its rate of reaction in systems containing simply alkali or lime.
From this review it is clear that measuring the degree of reaction of SCMs remains challenging. Nevertheless progress has been made in recent years to offer alternatives to the traditional selective dissolution methods. Unfortunately some of these -- image analysis and EDS mapping in the scanning electron microscope, and NMR - depend on access to expensive equipment and are time consuming. With regard to fly ashes, NMR seems to be reliable but limited to fly ash with low iron content. New methods with quantitative EDS mapping to segment fly ash particles from the hydrated matrix and to follow the reaction of glass groups of disparate composition separately look very promising, but time consuming. Sources with a high proportion of fine particles will have higher errors due to lower limit of resolution (1-2 \ensuremath{\mu}m). Whereas for SCMs which react relatively fast (e.g. slag, calcined clay) the methods based on calorimetry and chemical shrinkage seem promising on a comparative basis, the very low reaction degree of fly ashes before 28 days means that the calorimetry method is not practical. There is a lack of data to assess the usefulness of long term chemical shrinkage measurements. The possibility to quantify the amorphous phase by XRD is promising as this is a widely available and rapid technique which can at the same time give a wealth of additional information on the phases formed. However, the different reaction rates of different glasses in compositionally heterogeneous fly ashes will need to be accounted for and may strongly reduce the accuracy of the profile decomposition method.
This paper is the work of working group 2 of the RILEM TC 238-SCM {\textquotedblleft}Hydration and microstructure of concrete with supplementary cementitious materials{\textquotedblright}.},
  author       = {De Belie, Nele and Scrivener, Karen and Lothenbach, B and Gruyaert, Elke and Skibsted, J and Snellings, Ruben and Vollpracht, A and Villagran, Y},
  booktitle    = {14th International Congress on the Chemistry of Cement, Proceedings},
  editor       = {Shi, Caijun and Yao, Yan },
  keyword      = {filler effect,quantitative analysis,fly ash,Supplementary cementitious material,reaction degree},
  language     = {eng},
  location     = {Beijing, China},
  pages        = {1--12},
  title        = {Determination of the degree of reaction of fly ash in blended cement pastes},
  year         = {2015},
}

Chicago
De Belie, Nele, Karen Scrivener, B Lothenbach, Elke Gruyaert, J Skibsted, Ruben Snellings, A Vollpracht, and Y Villagran. 2015. “Determination of the Degree of Reaction of Fly Ash in Blended Cement Pastes.” In 14th International Congress on the Chemistry of Cement, Proceedings, ed. Caijun Shi and Yan Yao, 1–12.
APA
De Belie, Nele, Scrivener, K., Lothenbach, B., Gruyaert, E., Skibsted, J., Snellings, R., Vollpracht, A., et al. (2015). Determination of the degree of reaction of fly ash in blended cement pastes. In C. Shi & Y. Yao (Eds.), 14th International Congress on the Chemistry of Cement, Proceedings (pp. 1–12). Presented at the 14th International Congress on the Chemistry of Cement (ICCC2015).
Vancouver
1.
De Belie N, Scrivener K, Lothenbach B, Gruyaert E, Skibsted J, Snellings R, et al. Determination of the degree of reaction of fly ash in blended cement pastes. In: Shi C, Yao Y, editors. 14th International Congress on the Chemistry of Cement, Proceedings. 2015. p. 1–12.
MLA
De Belie, Nele, Karen Scrivener, B Lothenbach, et al. “Determination of the Degree of Reaction of Fly Ash in Blended Cement Pastes.” 14th International Congress on the Chemistry of Cement, Proceedings. Ed. Caijun Shi & Yan Yao. 2015. 1–12. Print.