What is Silica Fume

AK-SILICA FUME® under the “AK SILICA FUME” brand name is a brand, which has established itself as a superior cementitious material that can be used for producing high performance concrete presently, from our associate plants in India and China based on the Client’s requirement. Silica fume is a mineral admixture composes of very fine solid glassy spheres of silicondioxide (SiO2). Most Silica fume particles are generally 50 to 100 times finer than average cement or fly ash particles. Silica fume is a by-product of the industrial manufacture of ferrosilicon and metallic silicon in high temperature electric arc furnaces. The ferrosilicon or silicon product is drawn off as a liquid from the bottom of the furnace. Vapour rising from the 2000-degree-C furnace bed is oxidized, and as it cools condenses into particles, which are trapped in huge cloth bags. Processing the condensed fume to remove impurities and control particle size yields Silica fume.

  1. 1
    Product Description

    Silica Fume is a finely-divided mineral admixture, available in both uncompacted and compacted forms. It is a pozzolanic material which is composed of highly refined silicon dioxide in the non-crystalline form. Silica Fume will chemically react with the calcium hydroxide released by the hydration of portland cement to form compounds possessing superior cementitious properties. This ultra-fine material will better fill voids between cement particles and result in a very dense concrete with higher compressive strengths and extremely low permeability.

    Silica Fume is recommended for all types of concrete where improved concrete performance with reduced permeability is required to reduce the effect of corrosive chemicals, such as deicing salts, on structural steel. Silica Fume is also recommended where higher density and ultimate strengths are desired. Silica Fume does not contain calcium chloride, nitrates, nitrites or other potentially corrosive materials and is compatible with all standard concrete admixtures.

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    How does AK-Silica Fume Work ?

    Silica fume is added to concrete, initially it remains inert. Once portland cement and water in the mix start reacting with each other (hydrating), primary chemical reactions produce two chemical compounds: Calcium Silicate Hydrate (CSH), which is the strength producing crystallization, and Calcium Hydroxide (CH), a by-product also called free lime which is responsible for nothing much other than lining available pores within concrete as a filler or leaching out of inferior concrete. Pozzolanic reaction occurs between silica fume and the CH, producing additional CSH in many of the voids around hydrated cement particles. This additional CSH provides the concrete with not only improved compressive, flexural and bond- strength but also a much denser matrix, mostly in areas that would have remained as small voids subject to possible ingress of deleterious materials.

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    Advantages of AK- Silica Fume

    Silica Fume has been used all over the world for many years in the area where high strength and durable concrete were required. Silica Fume improves the characteristics of both fresh and hard concrete. The main benefits of using silica fume are:

    • Lowers concrete permeability
    • Significantly increases concrete durability.
    • Increases ultimate strength gain.
    • Significantly reduces alkali-silica reactivity.
    • Reduces steel corrosion.
    • Provides excellent resistance to sulfate or seawater attack.
    • Improves freeze/thaw durability of concrete.

  4. 4
    Compatibility of AK-SILICA FUME®

    Silica Fume is compatible with most air-entraining admixtures, calcium chloride and other admixtures. When used with other admixtures, each one must be dispensed separately into the mix.

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    Chemical and Physical Properties

    S.No Parameters AK-SILICA FUME®
    1 Silica (SiO2) (%) 94.42
    2 Ferric Oxide (Fe2O3) 0.48
    3 H2O (%) 0.68
    4 Alumina(AI2O3) 0.29
    5 Calcium Oxide(CaO)) 0.27
    6 Loss Of Ignition (%) 1.13
    7 Bulk Density (kg/m3) 610
    8 + 0.045mm (%) < 0.50
    9 – 0.045mm (%) > 99.5
    10 Active Index @ 7 days (%) 131

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    Health and Safety

    AK-SILICA FUME® is not considered to be hazardous to health; however it should be handled in accordance with good occupational hygiene and safety practices. High concentrations of dust may cause irritation. It is recommended that Personal Protective Equipment including eye protection, hand and skin protection and dust masks are worn when handling this product.



Highway bridges, parking decks, marine structures and bridge deck overlays are subject to constant deterioration caused by rebar corrosion current, abrasion and chemical attack.  Silica fume will protect concrete against deicing salts, seawater, traffic and heavy impact.  Rebar corrosion activity and concrete deterioration are virtually eliminated, which minimizes maintenance expense.


The use of silica fume in refractory castables provides better particle packing. It allows for less water to be used while maintaining the same flow characteristics. It also promotes low temperature sintering and the formation of mullite in the matrix of the castable. This produces a castable that has a low permeability to avoid gas, slag and metal penetration.


Silica-fume Shotcrete – delivers greater economy, greater time savings and more efficient use of sprayed concrete.  Silica fume produces superior shotcrete for use in rock stabilization, mine tunnel linings, and rehabilitation of deteriorating bridge and marine columns and piles.

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