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Condensed Silica Fume in Concrete

HSA Condensed Silica Fume

What is Condensed silica fume?

Condensed silica fume is a by-product of the manufacture of silicon or of various silicon alloys which are produced in so-called “submerged-arc electric furnaces”.

Condensed silica fume particles appear to be formed by the oxidation and condensa-tion of the gaseous silicon suboxide, SiO, which is formed in the reaction zone. When solidified condensed silica fume particles are entrained by the reaction gas or the reac-tion gas-air mixture coming from the furnace, they are collected in a dedusting system, generally in fabric bag filters.

As in many other highly technological industries, the silicon alloy producers have developed a whole range of specific products for specialized applications. Moreover, the customer’s specifications for silicon alloys have become more demanding so that a given producer must use different raw materials to produce a certain type of alloy. As different types of silicon alloys have been produced in submerged electric arc furnace, there have been correspondingly different types of condensed silica fume, just as there have been different types of fly ashes and slags, depending on the type of coal burned or the type of iron ore processed.

Condensed Silica Fume in Concrete
A series of complex chemical reactions occur in the furnace.

Production of Condensed Silica Fume

Schematic representatjon of silicon plants wjth and without aheat recovery system The type of alloy produced in a given furnace greatly influences the chemical com-position of the condensed silica fume recuperated in the bag-house because the tem-perature and the chemical reactions in the furnace depend on the type and amount of metal alloyed to silicon and on the impurities present in the metal or the ores intro-duced in the burden.

The use of wood chips in the burden can also influence to some extent the chemical composition of condensed silica fume, especially its carbon content, and also the loss on ignition (LOI) and the alkali content.

The design of the furnace, with or without a heat recovery system, not only influ-ences the color of condensed silica fume, but also its chemical composition, especially its carbon content. When the furnace is equipped with a heat recovery system gases leave the top of the furnace at about 800°C so that most of the carbon is com-pletely burned. In a conventional furnace, gases leave the furnace at about 200°C so that unburned carbon particles and some wood chips will be collected in the bag-house with condensed silica fume.

In addition, the chemical composition of quartz and coal, the two major compo-nents of the burden of the submerged-electric arc furnace, influences to some extent the chemical composition of condensed silica fume. Although these materials are gen-erally of high purity, they have to be very carefully selected and controlled.

Generally as the amount of silicon increases in the final product the level of chemical impurities in condensed silica fume decreases.

Condensed Silica Fume

Advantages of Condensed Silica Fume in Concrete

1. Very Stable Chemical and Physical Properties

Condensed Silica fume serves as a neutral filler with incredibly stable properties, both chemical and physical. It does not contain crystalline water, does not take part in the curing reaction, and does not impact the reaction process in any way.

2. Increased Thermal Conductivity

Not only can silica fume increase thermal conductivity, but it can also improve flame retardancy and change the adhesive velocity.

3. Good Adsorption Performance

Silica fume has a good adsorption performance, as well as good infiltration for various types of resin. In addition, it is easy to mix with no agglomeration phenomenon.

4. Reduced Precipitation and Stratification

Due to its reasonable distribution and fine grain size, silica fume can effectively eliminate stratification and reduce precipitation.

5. Improved Strength

The reasonable size distribution of silica fume ensures good hardness, strong densification, and great wear resistance. Adding silica fume to concrete can improve the wear resistance, compressive strength, and tensile strength of cured products. In addition, the abrasion resistance can be increased by 0.5-2.5 times.

6. Improved Insulation

Silica fume presents pure silicon powder with a low amount of impurities. As such, it possesses stable chemical and physical properties that ensure good arc resistance and insulation of the curing material.

7. Reduced Overall Costs

The bulk density of silica fume ranges between 0.2 and 0.8 or 1.0 and 2.2. When used as polymer filling material, microsilica can reduce the total cost of the product by saving the amount of polymer and minimizing the amount of loading.

8. Improved Corrosion Resistance

Silica fume is composed of silica, or SiO2, which is an inert material. This means that silica fume doesn’t react with most alkaloids or acids, and the silicon powder is evenly distributed over the surface of objects. As such, silica fume contributes to improved cavitation and corrosion resistance by 3 to 16 times.

9. Shortened Induction Period

Adding silica fume to concrete can shorten the induction period and provide early strength.

10. Crack Prevention

Silica fume can reduce the peak temperature achieved during the curing reaction of epoxy resin. In addition, it reduces the shrinkage rate and linear expansion coefficient in solidified concrete, thus reducing the internal stress and preventing cracking.

11. Improved Frost Resistance

The relative elastic modulus of microsilica is only 10 to 20 percent after 300-500 freeze-thaw cycles. At the same time, the average elastic modulus of usual concrete is 30 to 73 percent after 25-50 cycles. As such, adding microsilica to concrete can significantly improve its frost resistance.

Condensed Silica Fume Supplier

Henan Superior Abrasives is one of the largest suppliers of silica fume in China, we supply silica fume to many famous companies around the world, such as sika, elkem, etc. We can supply densified and undensified silica fume with 85%-99% silica content.We can also produce according to your requirement. The machine is automatically packed and filtered by a screen, so that no debris is mixed in.We are the only silica fume factory in China that uses machine packaging.

Feel free to contact us for the latest 2023 quotation of silica fume.



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