There are several main reasons why silica fume needs to be encrypted:
- Transportation cost problem:
Silica fume is a by-product recovered during the production of ferroalloys, which has very fine particles and very low density. Silica fume in its original density is bulky and expensive to transport. For example, the initial density of silica fume collected by the dust collector is only 150-200 kg/m³, which leads to a great expense in transportation. For example, a 60-ton train car can only carry about 18 tons when loaded with raw density silica fume, which makes transportation costs per ton of product sometimes as high as 50% of the selling price. Therefore, encrypted silica fume can be significantly reduced in size and transportation costs.
- Problems during use:
Silica fume is highly reactive, extremely easy to float and disperse, and prone to secondary pollution, affecting its performance and use. Unencrypted silica fume may float away through scraper conveyor or pneumatic conveying equipment in the process of use, causing environmental pollution and waste. Encrypted silica fume particles become coarser, the activity decreases, the dispersion becomes weaker, and it is not easy to float and scatter, thus reducing the risk of secondary pollution.
- Enhancement of application performance:
Encrypted silica fume is more widely and effectively used in concrete and other building material products. Researchers have found that the use of encrypted micro silica fume is more conducive to homogeneous mixing and improving the comprehensive performance of concrete, such as increasing strength, improving frost resistance, chemical erosion resistance and abrasion resistance. In addition, the transportability of encrypted silica fume has gradually improved to better meet the needs of different industries.
Encryption of silica fume is to solve the problems of its high transportation cost, easy to float and secondary pollution during use, and to enhance its performance in application.
There are mainly the following encryption methods for silica fume:
- Compressed air encryption method:
Produced silica fume is placed into a silo and then compressed air is blown in from the bottom of the silo causing the silica fume particles to tumble and agglomerate. – The heavier agglomerates fall to the bottom of the silo and are collected periodically. – These agglomerates decompose with the mix during concrete production.
2. Mechanical Compression Method：
Silica fume is loaded into molds and compressed under high pressure to make different shapes of industrial silica fume products. – This method is suitable for demanding industrial silica fume encryption and can produce products with high hardness, high density and flexible shapes. – However, it is not clear whether mechanically densified silica fume products are readily available in the market.
3. Ball milling method:
It is a commonly used method of industrial silica fume encryption, whereby silica fume is ground with sand by means of a ball mill to form high-density silica fume particles. – This method is suitable for the production of large-scale industrial silica fume with easy quality control and high stability.
- Wet encryption:
High density silica fume particles are prepared by utilizing the chemical reaction principle of wet method. – It needs to be made by mixing silica fume with a certain proportion of water, then adding chemical reaction agent, and made through several steps such as mixing, precipitation, filtration and drying.
When choosing the encryption method, the encryption process should be determined according to the use and requirements of the product. The main advantages of encrypted silica fume include savings in transportation costs (due to reduced volume and increased density), reduction of fugitive and secondary pollution, and the ability to improve the microstructure through physical and chemical action in the concrete paste, increasing the strength, frost resistance, chemical erosion resistance and abrasion resistance of concrete.
After encryption of silica fume, its performance is usually improved in the following aspects:
- increased density: After encryption of silica fume, its density increases, which helps to reduce transportation costs and storage space.
- Increased resistance to fly-away: Encrypted silica fume is not easy to fly-away, which reduces environmental pollution and waste.
- Improvement of concrete properties: As a concrete additive, encrypted silica fume can significantly improve the compressive strength, tensile strength, frost resistance, chemical erosion resistance and abrasion resistance of concrete.
- Microstructure Improvement: Adding encrypted silica fume to concrete can change its microstructure and make concrete denser, thus improving its durability.
- Increased abrasion resistance: Encapsulated silica fume can enhance the abrasion resistance of concrete, making it more durable.
- Improved impermeability: Encapsulated silica fume can improve the impermeability of concrete and reduce the penetration of water and harmful substances.
- Enhanced Thermal Stability: Encapsulated Silica Fume can improve the thermal stability of the concrete and keep its performance stable under high temperature environment.
- Enhanced environmental performance: The application of encrypted silica fume in concrete can reduce the amount of cement used, thereby reducing carbon dioxide emissions, which has environmental significance.
It should be noted that the degree of performance improvement after encryption of silica fume depends on its encryption process, product quality and application area. Therefore, when selecting and using encrypted silica fume, it should be evaluated and selected according to the specific needs and actual situation. At the same time, care should be taken to follow the relevant safety regulations and technical requirements during use.
Encrypted silica fume can be applied in several fields due to its improved physicochemical properties. The following are the possible application areas of encrypted silica fume:
- Field of building materials:
– **Exterior Wall Insulation, Moisture-proof, Dust-proof**: Encrypted silica fume can improve the thermal insulation, moisture-proof and dust-proof of the exterior wall of a building, thus improving the overall performance of the building.
– **Concrete additive**: encrypted silica fume, as a concrete admixture, can improve the microstructure of concrete and increase its strength, frost resistance, chemical erosion resistance and abrasion resistance. In addition, the revenue share of silica fume in the concrete sector is estimated to be high, which is the largest downstream application area of silica fume.
- Special fields:
– **Aerospace, Ship Anti-corrosion**: encrypted silica fume can be used in anti-corrosion treatments in aerospace and ships to protect metal surfaces from corrosion.
- Refractory materials:
– Encrypted silica fume can also be used in the production of refractory materials to improve the high-temperature strength and thermal shock properties of refractory materials by improving the fluidity and densification of the materials.
- Environmental field:
– Encrypted silica fume can also be used in wastewater treatment, utilizing its surface properties to remove harmful impurity ions in the water to purify the water.
- Other fields:
– Encrypted silica fume may also be used in ceramics, paints and coatings, plastics, rubber, metallurgical protective slag, chemical industry, papermaking, welding rods, and many other fields, depending on the degree of encryption and the desired physicochemical properties.
It should be noted that the application areas of encrypted silica fume may vary depending on its encryption process, product quality and market demand. Therefore, when selecting encryption silica fume, the applicable encryption methods and product specifications should be determined according to the specific application scenarios and needs. At the same time, care should be taken to follow the relevant safety regulations and technical requirements during use.