Silica Fume (SF90)

Microsilica - Physical Properties
Particle Size Most particles are sub-micron. Average particle diameter is 0.15 microns, about 100x smaller than cement
grains.

Particle Shape Smooth, spherical particles.
Density (Specific Gravity)
Approximately 2.2 (cement is typically 3.1)
Specific Surface Area
Ranging from 15 000 to 30 000 m2/kg (measured by nitrogen-absorption - BET)

Microsilica - Chemical Properties
Minimum 85% SiO2 (normally 90+%) 

 Amorphous Reactive Silica

Pozzolanic - reacts with Ca(OH)2

LOI - preferably less than 4%