microsilica - sioxid®


MICROSILICA - SIOXID /Type II Admixture/ is a finely dispersed powdered material of a gray color. MICROSILICA - SIOXID /Type II Admixture/ is a by-product originating from the production of ferrosilicon in electric arc furnace (EAF). Fine-grained condensed fumes of silicon dioxide are collected by bag house filters in dedusting units.

For silica fume used as a material for concrete MICROSILICA – SIOXID /Type II Admixture/, the harmonized standard STN EN 13263-1:2005 +A1:2009, declaration of parameters of the manufacturer no. 01/2019/CPR and the certificate of constancy of performance 1301 – CPR – 0432 shall apply.

Physical properties

Apparent density of silica fume in its original undensified form is roughly 130 to 450 kg/m3. For improving handling and transportation silica fume can be densified into micropelletized form with higher apparent density of 450 to 650 kg/m3. Fineness of material as characterized by specific surface measured by nitrogen absorption method (BET) normally ranges from 15 to 35 m2/g. Most particles are within a diameter of 0.1 to 0.2 μm. Loss on ignition as measured by L. O. I. method is max. 4 % at 750°C.

Intended use

Silica Fume for concrete MICROSILICA – SIOXID /Type II Admixture/ is used as follows:

manufacturing of prefabricated materials intended for reconstructing and reprofiling of constructions made of concrete and reinforced concrete, the weight proportion of MICROSILICA – SIOXID /Type II Admixture/ is 2.5 – 10 % w/w out of binding material;
manufacturing of concretes with special properties, the weight proportion of MICROSILICA – SIOXID /Type II Admixture/ as additive into cement typically ranges from 5 to 15 % w/w;
cement manufacturing in accordance with STN EN 197-1;
rubber and woodworking industry, as well as non-construction sectors and industries

Packing and Transport

The material is supplied in its original form packed in coverings such as big bags, bags, or barrels with loading onto motor vehicles. A loose material can be transported in cisterns. MICROSILICA - SIOXID /Type II Admixture/ can also be delivered as pelletized material available upon customer request.

Size of particles (μm)

Typ. 0.1 - 0.2

Bulk density (kg/m3)
0 - 450
450 - 600
min. 600
Chemical Analysis %
Elementary Si
Sulphates (SO3)
Total Alkali Content (Na2O equiv.)
Chlorides (Cl-)
Loss on Ignition
min. 85.0
max. 0.4
max. 1.0
max. 2.0
max. 6.0
max. 0.3
max. 4