Special Chemical Concrete Admixture Fine Granular Powder Micro Silica Fume with High Reactive Pozzolanic

Properties of Silica Fume

CAS No.

69012-64-2

Particle shape

Powder

Color

Dark grey / Light grey

Amorphous

This term simply means that silica fume is not a crystalline material. A crystalline material will not dissolve in concrete, which must occur before the material can react. 

Silicon dioxide (SiO2)

85% to 97 %

This is the reactive material in silica fume. Because of its very high amorphous silicon dioxide content, silica fume is a very reactive pozzolanic material in concrete. As the portland cement in concrete begins to react chemically, it releases calcium hydroxide. The silica fume reacts with this calcium hydroxide to form additional binder material called calcium silicate hydrate. It is largely this additional binder that gives silica-fume concrete its improved hardened properties.

Bulk density

280-400 kg/m3 (Undensified) / 550-700 kg/m3 (Densified)

The bulk density of the as-produced fume depends upon the metal being made in the furnace and upon how the furnace is operated. Because the bulk density of the as-produced silica fume is usually very low, it is not very economical to transport it for long distances.

Specific surface area:

15000-27000m2/kg

Specific surface is the total surface area of a given mass of a material. Because the particles of silica fume are very small, the surface area is very large. We know that water demand increases for sand as the particles become smaller; the same happens for silica fume. 

Particle size

 < 1 µm

Silica fume particles are extremely small, with more than 95% of the particles being less than 1 µm . Particle size is extremely important for both the physical and chemical contributions of silica fume in concrete.

Specific gravity

2.2

Specific gravity is a relative number that tells how silica fume compares to water, which has a specific gravity of 1.00.  Silica fume has a specific gravity of about 2.2, which is somewhat lighter than portland cement, which has a specific gravity of 3.15. Thus, adding silica fume to a concrete mixture will not “densify” the concrete in terms of increasing the density of the concrete.