Type | SiO2 | Al2O3 | Fe2O3 | LOI | PH |
SF-95 | 95%Min | 1.0%Max | 1.0%Max | 4%Max | 4.5-7.5 |
SF-92 | 92%Min | 1.0%Max | 1.0%Max | 5%Max | 4.5-7.5 |
SF-90 | 90%Min | 2.0%Max | 2.0%Max | 5%Max | 4.5-7.5 |
SF-85 | 85%Min | 2.5%Max | 2.5%Max | 6%Max | 4.5-7.5 |
Package:
Because of its extreme fineness and high silica content, silica fume is a very effective pozzolanic material. Standard specifications for silica fume used in cementitious mixtures are ASTM C1240, EN 13263.
Silica fume is added to Portland cement concrete to improve its properties, in particular its compressive strength, bond strength, and abrasion resistance. These improvements stem from both the mechanical improvements resulting from addition of a very fine powder to the cement paste mix as well as from the pozzolanic reactions between the silica fume and free calcium hydroxide in the paste.
Addition of silica fume also reduces the permeability of concrete to chloride ions, which protects the reinforcing steel of concrete from corrosion, especially in chloride-rich environments such as coastal regions and those of humid continental roadways and runways (because of the use of deicing salts) and saltwater bridges. Furthermore, Silica Fumes has important uses in oil and gas operations. Silica fume can be used for a primary placement of grout as a hydraulic seal in the well bore, or secondary applications such as remedial operations including leak repairs, splits, and closing of depleted zones.
Prior to the mid-1970s, nearly all silica fume was discharged into the atmosphere. After environmental concerns necessitated the collection and landfilling of silica fume, it became economically viable to use silica fume in various applications, in particular high-performance concrete.Effects of silica fume on different properties of fresh and hardened concrete include: