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Factors That Determine The Color Of Silica Fume


Silica fume is a by-product of ferrosilicon smelting, and is used in high-strength concrete, refractory castables, etc. Also, as a mineral admixture, silica fume is often used in wall decorative patching materials such as cement plaster to increase their strength and durability. Usually we see the silica fume are gray, used in wall decoration or repair material may affect the color of the wall, then the silica fume color has white? The answer is certain.

The color of silica fume

In fact, the color of silica fume is not only one kind of gray, there are dark blue, blue-black, off-white, white, black, etc. Different colors represent the different content of various elements in its composition, but the silica content is between 80% and 96%. Generally speaking, gray and dark gray silica fume are used in the preparation of high-strength concrete, while black and other heavier colors are used in the preparation of refractory materials, and white is mostly used in insulation materials, chemical coatings, oil well cement and other fields.

The factors that determine the color of silica fume

  1. The silica in the silica fume itself is colorless, but because the silica fume is collected, the coke in the powder and wood chips, etc. will be combined with it, so that the silica fume has a different color; according to the different furnace temperatures in ferrosilicon smelting, the reaction produced by many elements in the dust is different, and the color will have a gap.
  2. According to different ferrosilicon smelting process, the smelting process may use different materials, and the main factor that determines the color of silica fume is the content of carbon and iron oxide, when their content is less, the more white the color of silica fume, the higher the content of carbon or iron oxide, the darker the color of silica fume, or even blackened.
  3. After the silica fume is collected, the dispersion is larger, and it is more difficult to transport and use, so it usually undergoes certain encryption treatment, and the encrypted silica fume will be slightly darker than before it is encrypted because the pores become smaller and the particles are closer together.

The content of the constituent elements of silica fume

Usually the color of the silica fume cannot be artificially controlled, after all, each time the silicon smelting process can not be exactly the same, so the color between the previous and subsequent batches will not be the same, then there will be partners worried about the quality of different colors of silica fume, I think here is not necessary, because no matter which color of silica fume, its elemental composition and content are strict standards, even if the black silica fume The following is the content of each element in the different specifications of silica fume, you can refer to:

Composition Index Specification
SF96 SF93 SF90 SF88
SiO2 96% 93% 90% 88%
AL2O3 1.0% 1.0% 1.5%
Fe2O3 1.0% 1.0% 2.0%
CaO+MgO 1.0% 1.5% 2.0%
K2O+Na2O 1.0% 1.5% 2.0%
C 1.0% 2.0% 2.0% 2.5%

From the content of each constituent element in the above table can be seen, in fact, the color of microsilica powder and microsilica powder specifications are not directly related, although there are differences in iron oxide content and carbon content in different specifications, but it does not mean that the same specifications of microsilica powder color is the same, which is not necessarily.

Because each batch of silica fume color is not possible to maintain consistent, so when the purchase of color requirements, must be determined in advance with the silica fume manufacturer consultation, otherwise the purchase of products that do not meet the requirements of use is not good. Henan Superior Abrasives has close cooperation with many domestic research institutes in order to provide users with different content, specifications and colors of micronized silica powder, if you need, you can leave a message on our website or call our customer service for detailed consultation.

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