Definition
Silica fume (also called microsilica), is a co-product of silicon or ferrosilicon production, consisting of ultrafine (sub-micron), amorphous, non-porous, perfectly spherical silicon dioxide (SiO2) particles, with purity levels of 85 to 99 %. The main effect of these ultra-fine particles is to greatly improve particle packing and produce a highly pozzolanic reaction in concrete and other cementitious bond systems where the silicon dioxide reacts with calcium hydroxide, heightening performance levels and the strength and durability of these materials. Additionally, silica fume, because of its amorphous (non-crystalline) structure and its specific area, provides other useful features to various applications, including improved sintering capabilities and enhanced high-temperature performance of refractory castables, resulting in reactions between microsilica and other components of the refractory mix.
Production
Silica fume is a byproduct in the carbothermic reduction of high-purity quartz with carbonaceous materials like coal, coke, and wood chips, in electric arc furnaces in the production of silicon and ferrosilicon alloys.
Densification and Bulk Density
| Undensified Silica Fume (260~450kg/m³) | Undensified Silica Fume Grade 85U，90U，92U， 94U，95U，96U，99.9U |
| Densified Silica Fume (500~650 kg/m³) | Densified Silica Fume Grade 85U，90U，92U， 94U，95U |
Whether you’re a paints and coatings or concrete manufacturer, at Ewende, we supply both high-quality silica fumes to help you meet local standards and industry specifications. Before shipping our products, we ensure that they are thoroughly inspected so you can be sure to achieve the desired results. Get in touch with us today to get specifications or a quote and discover how we can help you meet your upcoming projects’ needs.
Color
The color of silica fume ranges from light gray to dark gray. There is also a white silica fume with both SiO2 and ZrO2 content.
Factors that influence the color of silica fume:
- Raw material, reductant: Since SiO2 is colorless, the color is influenced by other content such as carbon and iron oxide. Under normal conditions, silica fume collected from silicon metal, high purity silicon has darker colors than that collected from ferrosilicon.
- Time: Silica fume produced from smelters that just started operating has darker colors than from smelters that have operated for more than 2 or even 6 months.
- Bulk density: Typically, the higher the density, the darker the color.
- Temperature in smelters.
- Conditions of smelters.
The working principle of silica fume
Due to its very small particle size (over 100 times finer than cement) and high SiO2 content, Silica Fume is a highly reactive pozzolan. This means it will react with the calcium hydroxide [Ca(OH)2] produced when cement hydrates. The small particle size means that the silica fume fills the spaces between the cement grains, improving the rheology of the mix and reducing the voids in the concrete. The ‘pozzolanic reaction’ with the Ca(OH)2 increases the amount of calcium silicate hydrates (CSH) produced, which intensifies the bond to the aggregates and improves the homogeneity of the mix, reducing porosity and permeability and increasing the strength.
“High-Performance Concrete” is usually designed to incorporate silica fume, and sometimes other pozzolans, to achieve targeted characteristics for the structure being built. These can be flow or pumping performance, or enhanced durability, such as increased toughness, increased resistance to abrasion, corrosion and chemicals, and life-cycle cost efficiencies. Highway bridges, parking decks, marine structures and bridge deck overlays are subject to constant deterioration caused by reinforcing steel corrosion, abrasion and chemical attack. Silica Fume will protect concrete against de-icing salts, seawater and abrasion from road traffic. Reinforcing steel corrosion and concrete deterioration are virtually eliminated, minimizing maintenance costs.
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Applications:
- In construction, the Ewende line of products improves the performance of a wide range of construction materials in a variety of applications:
- High-performance concrete with microsilica reduces construction time and provides structural advantages and durability for buildings, bridges, transport tunnels, roadways, etc.
- Fiber cement with microsilica is used in roofing materials, such as flat and corrugated sheets, tiles, pipes and moldings for new structures or to efficiently help replace asbestos.
- Gypsum board with microsilica improves fire resistance and core strength.
- For refractory materials, Ewende Silica Fume offers the following advantages:
- Improved strength and service life in high-temperature applications
- Compatible with the making of complex structures, such as castables and shaped parts, thanks to good placement characteristics and low porosity, combined with excellent heat resistance properties.
- For oilfield cementing operations, Ewende Silica Fume Powder offers the following advantages:
- There are numerous microsilica additives to ensure essential bonding and mechanical properties.
- Applied to the mix design of high-performance concrete:
- compatibility: the compatibility of micro silicon fume powder with water-reducing agents, fly ash, mineral powder, fiber and others is good.
- slumps: due to the interstitial effect, concrete viscosity is higher, so the silica fume concrete slumps design requirement is higher by 2 – 3 cm than the ordinary concrete;
- the amount of silica fume added (added amount): making high strength and shotcrete, the added microsilica amount is 6-12% of cement; for underwater engineering, its amount is higher; When the microsilica fume is used as pump aid, the mixing amount is reduced to 2%. The final mix ratio is determined by the mixing ratio test.
- Micro silica fume and cement, aggregate are stirred at the same time, strictly according to standard construction, and maintenance must be strengthened at the same time.
Silica Fume Supplier in China | Ewende
Ewende is one of the professional Silica Fume Suppliers in China, and also the premium source of high-performance Silica Fume products for concrete and refractory industries.
As a crucial supplier of Silica Fume, we have gained credit from our excellent guests and have been maintaining stable and long-term business cooperation, owing to our advanced tech, reasonable price, varied packages and good service. Our market covers Australia, America, Canada, Japan, Southeast Asia, etc.
Welcome to visit our factory, if you have any needs or any questions, please contact us.
