Q. What is Silica Fume?
A. It is a by-product in the production of certain types of steel.
Q. What is special about Silica Fume?
A. The particles are much smaller than cement. They are over 90% silicon and can react with the calcium hydroxide in cement. When they react they are able to fill and seal the space between particles of cement.
Q. What are the primary properties imparted by Silica Fume in concrete?
A. Low permeability, high compressive strength and high abrasion resistance. The low permeability is desirable in concretes that have steel and are exposed to de-icing salts or saltwater such as in bridge decks and marine docks.
Q. Do I just need to add Silica Fume to concrete to make it stronger?
A. No. Silica Fume needs to react in a low water:cement ratio environment to be able to develop high strength and low permeability. Silica Fume should be used along with a water reducer for best performance.
Q. Are there any other applications for Silica Fume?
A. Yes. In shotcrete it is used to reduce the rebound of material and to impart high strength.
Q. How is color affected when using Silica Fume?
A. Silica Fume is dark gray in color. Concrete with Silica Fume will be darker in color.
Q. Are there any special requirements for placing, finishing and curing concrete with Silica Fume?
A. Yes. Since Silica Fume concrete has a low water cement:ratio it is important to prevent drying and moist curing is very important. For additional information contact Fritz-Pak.
Q. Is Silica Fume harmful to humans?
A. No. Silica Fume is an amorphous form of Silicon and does not promote silicosis in humans. However, respirators are required for handling the product, since Silica Fume particles are very small and can easily become airborne.
Q. Are Silica Fume and Fumed Silica the same?
A. No. Silica Fume is a by-product of steel production. Fumed Silica is a precipitated form of silicon dioxide that is produced chemically. Fumed Silica is much more expensive that Silica Fume and does not provide the same characteristics to concrete.