This graph shows that adding increasing amounts silica fume greatly
increases the water demand for a constant-slump concrete. To be able to
produce low water-cementitious materials ratio concrete, it is essential to
use a high-range water-reducing admixture in conjunction with the silica
fume.
As the w/cm becomes lower and lower for higher and higher levels of
performance, it is not unusual to greatly exceed the manufacturer's
recommendations on HRWRA dosage. This practice is not usually a problem,
but be sure to look at the effect of the increased admixture on your time of
setting.
This figure is taken from: V. M. Malhotra and G. G. Carette, "Silica Fume
Concrete -- Properties, Applications, and Limitations," Concrete
International, Vol. 5, No.5 , pp. 40-46.
The Silica Fume Association
38860 Sierra Lane, Lovettsville, VA 20180
Tel: 540.257.4224 Fax: 540.822.9456
