Socket where a sand grain has been pulled away from cement paste in 28-day
old mortar containing silica fume. The sand grain was originally at the top
of the picture. Note the dense structure without the gaps and crystals seen
in the previous photo. "When 15% CSF by weight of cement is added to the
mortar, the microstructure of the interfacial zone is significantly changed.
Its structure is homogeneous and dense without the presence of a massive CH
rim or gaps. These changes can be the result of the suppression of bleeding
in the fresh mortar and the ability of the CSF particles to fill the space
in the vicinity of the sand grain surface much more efficiently than the
bigger cement particles." "The effect of CSF on densifying and homogenizing
the microstructure of the interfacial zone may have a considerable influence
on the performance of mortars and concretes. Therefore, when the effect of
CSF on mortars and concretes is being considered, the interfacial effects
should be taken into account in addition to the influence of the CSF on the
bulk paste matrix." Arnon Bentur and M. D. Cohen, "Effect of Condensed
Silica Fume on the Microstructure of the Interfacial Zone in Portland Cement
Mortars," Journal of the American Ceramic Society, Vol. 70, No. 10, pp.
738-743, 1987.
The Silica Fume Association
38860 Sierra Lane, Lovettsville, VA 20180
Tel: 540.257.4224 Fax: 540.822.9456
