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Effect of fly ash on the microstructure of cement mortar

Xu, A.; Sarkar, S.L. and Nilsson, Lars-Olof LU (1993) In Matériaux et Constructions 26(161). p.414-424
Abstract
A microstructural study of mortars prepared with a low-alkali, low-C3A cement and a Class F fly ash, both of Swedish origin, was carried out using the scanning electron microscopy - energy-dispersive X-ray analytical technique. Supplementary phase analyses were made by X-ray diffraction and thermogravimetry -differential thermal analysis. Normally, CH crystals in the transition zone grow with their c axis parallel (or the (001) cleavage plane perpendicular) to the aggregate surface. The encapsulation of the fly ash particles by the growing CH reduces the amount of orientated CH at the aggregate - paste interface. The growth mechanism of these crystals is discussed. The reduction of CH, most significant after 28 days of hydration, is mainly... (More)
A microstructural study of mortars prepared with a low-alkali, low-C3A cement and a Class F fly ash, both of Swedish origin, was carried out using the scanning electron microscopy - energy-dispersive X-ray analytical technique. Supplementary phase analyses were made by X-ray diffraction and thermogravimetry -differential thermal analysis. Normally, CH crystals in the transition zone grow with their c axis parallel (or the (001) cleavage plane perpendicular) to the aggregate surface. The encapsulation of the fly ash particles by the growing CH reduces the amount of orientated CH at the aggregate - paste interface. The growth mechanism of these crystals is discussed. The reduction of CH, most significant after 28 days of hydration, is mainly due to the reaction of CH with the fly ash glass phase. Initially, the replacement of cement by fly ash weakens the paste - aggregate interfacial zone due to reduction of contact points, and increases the local water-to-cement ratio. This, however, improves significantly when the fly ash has reacted. In order to enhance the reaction of fly ash, extra gypsum was added. The results show that gypsum can accelerate the fly ash reaction, but the products formed, and the beneficial effects of gypsum, are mainly determined by the total amount of gypsum in the paste. (Less)
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author
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Paste aggregate interfacial zone, Composition effects, Cements, Concrete aggregates, Crystal growth, Differential thermal analysis, Fly ash, Gypsum, Gravimetric analysis, Interfaces (materials), Microstructure, Scanning electron microscopy, Cement mortar, X ray analysis, Water to cement ratio
in
Matériaux et Constructions
volume
26
issue
161
pages
414 - 424
publisher
Springer
external identifiers
  • scopus:0027642903
ISSN
0025-5432
DOI
10.1007/BF02472942
language
English
LU publication?
no
id
a7c7b0ce-d9be-424e-b480-e03e492622ec (old id 1485707)
date added to LUP
2009-10-05 10:52:40
date last changed
2017-08-13 04:15:08
@article{a7c7b0ce-d9be-424e-b480-e03e492622ec,
  abstract     = {A microstructural study of mortars prepared with a low-alkali, low-C3A cement and a Class F fly ash, both of Swedish origin, was carried out using the scanning electron microscopy - energy-dispersive X-ray analytical technique. Supplementary phase analyses were made by X-ray diffraction and thermogravimetry -differential thermal analysis. Normally, CH crystals in the transition zone grow with their c axis parallel (or the (001) cleavage plane perpendicular) to the aggregate surface. The encapsulation of the fly ash particles by the growing CH reduces the amount of orientated CH at the aggregate - paste interface. The growth mechanism of these crystals is discussed. The reduction of CH, most significant after 28 days of hydration, is mainly due to the reaction of CH with the fly ash glass phase. Initially, the replacement of cement by fly ash weakens the paste - aggregate interfacial zone due to reduction of contact points, and increases the local water-to-cement ratio. This, however, improves significantly when the fly ash has reacted. In order to enhance the reaction of fly ash, extra gypsum was added. The results show that gypsum can accelerate the fly ash reaction, but the products formed, and the beneficial effects of gypsum, are mainly determined by the total amount of gypsum in the paste.},
  author       = {Xu, A. and Sarkar, S.L. and Nilsson, Lars-Olof},
  issn         = {0025-5432},
  keyword      = {Paste aggregate interfacial zone,Composition effects,Cements,Concrete aggregates,Crystal growth,Differential thermal analysis,Fly ash,Gypsum,Gravimetric analysis,Interfaces (materials),Microstructure,Scanning electron microscopy,Cement mortar,X ray analysis,Water to cement ratio},
  language     = {eng},
  number       = {161},
  pages        = {414--424},
  publisher    = {Springer},
  series       = {Matériaux et Constructions},
  title        = {Effect of fly ash on the microstructure of cement mortar},
  url          = {http://dx.doi.org/10.1007/BF02472942},
  volume       = {26},
  year         = {1993},
}