Micro Silica Chemical Composition

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Basic physical properties of micro silica:

◇ Existing form: amorphous ultra-fine (amorphous) powder
◇ Typical color: gray (the natural state is grayish white, and the color gradually deepens with the increase of density)
◇ Specific surface area: 15~28 m2/g
◇ Loose bulk density: 200~350 kg/m3
◇ Activity index: ≥ 85%
◇ Water demand ratio: ≤ 125%

The main chemical component of micro silica powder is SiO2, with content of 85~97%. Its elements include Fe2O3, Al2O3, CaO, K2O, Na2O, MgO, C, etc.

Comparison of physical properties of micro silica fume with cement, slag and fly ash:

Project Silica Fume Cement Slag Fly Ash
Proportion(N/m3) 21000 31500 29000 21000
Density(kg/m3) 200-300 1200-1400 1000-1200 900-1000
Loss on ignition(%) 2-4 12
Specific surface area(m2/kg) 20000 200-500 200-600

Micro silica chemical composition in the world:

Physical and chemical properties United States Europe Canada Japan China Brazil South Korea Italy
SiO2 (%) ≥ 85.0 ≥ 85.0 ≥ 85.0 ≥ 85.0 ≥ 85.0 ≥ 85.0 ≥ 85.0 ≥ 85.0
SO3 (%) < 2.0 < 1.0 < 3.0 < 3.0
cl (%) < 0.3 < 0.1 < 0.2 < 0.3
free Cao (%) < 1.0 < 1.0
MgO (%) < 5.0 < 5.0
free Si (%) < 0.4
Alkali content (%) < 1.5 < 1.5
Humidity (%) < 3.0 < 3.0 < 3.0 < 3.0 < 3.0
Ignition loss (%) < 6.0 < 4.0 < 6.0 < 5.0 < 6.0 < 6.0 < 5.0 < 4.0
Specific surface area (m2/g) > 15 15-35 > 15 > 15 > 15 > 15
Activity indicators (%) > 105@7d > 95@7d> 105@28d > 85@28d > 95@7d > 85@7d
Particle size ( 45um triage %) < 10 < 10 < 10 < 5.0 < 10
The average particle size (%) < 5 < 5
Water requirement ratio (%) < 125

The United States, Canada, Norway and other countries have formulated specifications (standards) for the use of silica fume:

          Project
Country
SiO2 SO3 Loss on ignition Maximum allowable usage
Canada > 85 < 1 < 6 < 10
United States > 85 < 1 < 6 < 10
Norway > 85 < 1 < 8