Undensified Silica Fume, also known as raw silica fume or primary silica fume, is a by-product of the high-temperature smelting of ferrosilicon in industrial electric furnaces.
What is raw silica fume (primary silica fume)?
Raw silica ash is a gaseous dust released during the production of silicon metal or ferrosilicon alloy at high temperatures and collected by condensation. It has the characteristics of large specific surface area, high activity and small fineness. Because of its low bulk density of approximately 200+ kg per cubic meter, it is larger than the equivalent weight of encrypted silica fume, which can increase costs in terms of transportation.
Production process of Undensified silica fume
Exhaust gas purification
The flue gas exported from the electric furnace passes through the fume hood, the main flue gas pipeline, cools down through the cooler and then enters the cyclone separating dust collector, and then passes through the cloth bag dust collector. The flue gas enters the bag filter through the fan, the dust is trapped down by the inner surface of the filter bag, and the purified flue gas which meets the environmental protection standard is discharged from outside the filter bag and rises to the top of the dust collector to be discharged into the atmosphere through the emission port.
Silica Fume collection
When the equipment running resistance or time reaches the set value, the ash unloading process starts. Using the negative pressure of the front section of the main fan, the process of cleaning silica dust from each compartment of the bag dust collector is realized through the switch of the anti-suction duct and the inlet and outlet duct valves, and the recovered dust is sent to the Silica Fume homogenizing device by the fan through the ash conveying duct.
Encryption processing (Densified Silica Fume)
When making silica fume, manufacturers often carry out the third step, which is encryption processing. Considering the transportation cost, and other specific application needs, silica fume manufacturers will provide different microsilica according to the customer’s situation, so this is the reason why encrypted microsilica is more popular. However, Undensified silica fume also has many advantages.
What are the advantages of Undensified silica fume?
Silica Fume is often encrypted, which is also due to the characteristics of the Undensified silica fume itself, low bulk density resulting in higher transport costs, manufacturers need to invest more packaging costs, in addition, the Undensified silica fume is more active, easy to drift caused by the phenomenon of fly ash on site feeding, resulting in secondary pollution. However, there are always two sides of a coin, there are disadvantages which means that it also has advantages, the Undensified silica fume also has the advantages of other types of silica fume do not have, as follows.
The Undensified silica fume is more convenient to use, because of the characteristics of small particles, easy to disperse, basically do not need to increase the concrete mixing time. It has the characteristics of increasing the compressive and flexural strength of concrete, water penetration resistance, good filling effect and good adaptability to water reducing agents. The color of as-built silica fume will be lighter than that of encrypted silica fume, so it will not deepen the color of concrete.
Silica fume improves the performance of concrete through physical and chemical mechanisms. Physical mechanisms include reducing bleed-through, providing nucleation point formation, and filling solid particles more efficiently.
Reduced permeability: Silica fume in fresh concrete significantly reduces permeability and enhances cohesion as a physical effect, the result of incorporating very fine particles into the mix. The higher the silica fume content, the more pronounced the effect. Enhanced bonding will benefit the hardened concrete structure by reducing segregation and gaps in the reinforcement and coarse aggregates.
Provide nodule point formation: Silica fume accelerates the hydration reaction of cement by providing nodule points in the early stages, in which the cement hydration products are more easily resolved from solution to form nodule points.
Granular packing: In hardened concrete, silica fume particles improve the filling of the solid material by occupying the gaps between cement particles, just as cement occupies the gaps between particles of fine aggregate, which in turn occupy the gaps between particles of coarse aggregate, an analogy that applies only when the surface forces between cement particles are negligible, i.e., when sufficient water reducing agent is present to overcome the effect of surface forces . In most concretes used for construction purposes, the addition of more silica fume leads to an increase in water demand, requiring the use of water reducers to increase workability.
To know the Difference Between Densified and Undensified Silica Fume, please visit: https://hsamaterial.com/blog/difference-between-densified-and-undensified-silica-fume.html
Although the Undensified silica fume has its own performance limitations, however, it also has many advantages, specific areas of use can be consulted Silica Fume manufacturer Henan Superior Abrasives, we can provide customers in different industries with different uses of high quality microsilica powder and provide technical support throughout the process, welcome your consultation.
