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Microstructure of entrained air voids in concrete, Part I

Published online by Cambridge University Press:  31 January 2011

Ahmed I. Rashed  and
Robert Brady Williamson
Ahmed I. Rashed
Affiliation:
Department of Civil Engineering, University of California, Berkeley, California 94720
Robert Brady Williamson
Affiliation:
Department of Civil Engineering, University of California, Berkeley, California 94720
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Abstract

The microstructure of air voids in both air-entrained and non air-entrained paste, mortar, and concrete has been studied at different ages (5 min to 60 days) in order to understand how air-entrained voids form in portland-cement systems. Scanning electron micrographs of air voids are presented for different ages. The solidification process of portland-cement paste and mortar was frozen at different ages using a low temperature scanning electron microscope and freeze drying. At very early ages the air voids show thin shells made of very fine particles. The packing of the cement grains behind the air void varies, depending on the water-to-cement ratio. Air voids appear to have the same interface with the cement paste matrix as aggregates. No readily visible difference was found between entrapped and entrained air voids.

Type
Articles
Information
Journal of Materials Research , Volume 6 , Issue 9 , September 1991 , pp. 2004 - 2012
Copyright
Copyright © Materials Research Society 1991

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