Micro silica fume (scientific name “silica fume” or microsilica). It is amorphous and powdery silicon dioxide (SiO2) collected by a specially designed dust collector after oxidizing the silicon vapor discharged from the flue when smelting ferrosilicon and processing industrial silicon. The average particle size of silica fume is 0.1-0.15um, which is a few percent of the average density of cement. The specific surface area is 15-27m2/g, with strong surface activity.
Classification of microsilica fume
1. According to the content
We know that micro-silica fume is mainly composed of silicon dioxide, so according to national standards, micro-silica fume is generally divided according to the content of SiO2:
(1) When the SiO2 content is greater than or equal to 88%, it is called SF88 type micro-silica fume. The main production control requirement is the loss on ignition, and the loss on ignition should be less than or equal to 6%;
(2) When SiO2 is greater than or equal to 90%, it is called SF90 type micro-silicon powder. On the basis of the previous level, the main control is its related impurities, which is mainly determined according to the needs of customers;
(3) When SiO2 is greater than or equal to 93%, it is called SF93 type micro-silica powder. Products of this specification have specific requirements for the content and performance of various impurities, especially fluidity;
(4) When SiO2 is greater than or equal to 96%, it is called SF96 type micro-silica fume. This grade of micro-silica fume has very strict requirements on impurity content and performance, and the requirements for PH value are also strict.
2. Divide by density
According to different densities, micro-silica fume has different performances. It is mainly divided into original micro-silica fume, mildly encrypted micro-silica fume, semi-encrypted micro-silica fume and high-density micro-silica fume:
(1) The density of the original micro-silica fume is 100 to 170kg/m³, its structure is relatively dispersed, and its conveying performance is poor, but its bonding ability is strong after encountering water;
(2) The density of lightly encrypted micro-silica fume is 250 to 400kg/m³, which basically does not appear granular, but the conveying performance is obviously improved, but it is easily affected by temperature;
(3) The density of the semi-encrypted micro-silica fume is 400 to 500kg/m³. The micro-silica fume of this density has a large number of loose particles, which are not easy to bond and have good conveying performance;
(4) The density of high-density micro-silica fume is 500 to 700kg/m³. The shape of high-density micro-silica fume is basically dominated by hard particles. According to different grades, the particle size and tightness are different, and have excellent conveying performance.