Undensified Silica Fume

Undensified Silica Fume, also known as raw silica fume or primary silica fume, it is chemically similar to densified silica fume, but with a different density. This type of silica fume is incredibly light, has a density of 250-350 kg/m3, is very active, and requires a large storage space.

Undensified silica fume is more convenient to use, because of the characteristics of small particles, easy to disperse, and basically does 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 the as-built silica fume will be lighter than that of densified silica fume, so it will not deepen the color of the concrete.

Elevate your concrete projects to new heights with Ewende’s premium Densified Silica Fume offerings. Choose from an array of grades, including the sought-after 99.9% Undensified Silica Fume, our star product. Tailored to perfection, our Grade 85D, 90D, 92D, 94D, 95D, and 96D options empower concrete manufacturers and construction endeavors with exceptional silica content and densities. Experience the future of concrete innovation, crafted to your precise needs.

The low bulk density of Undensified silica fume leads to higher transport costs, and manufacturers need to invest more in packaging costs, in addition, the Undensified silica fume is more active and easy to drift caused by the phenomenon of fly ash on-site feeding, resulting in secondary pollution.

Silica fume is formed when ferrosilicon and industrial silicon (metal silicon) are smelted, a large amount of highly volatile SIO₂ and Si gas are produced in the submerged electric furnace, and the gas is quickly oxidized, condensed and precipitated with air after the gas is discharged. It is a product of large-scale industrial smelting. The whole process needs to be recycled with dust removal and environmental protection equipment, because the quality is relatively light, and it needs to be encrypted with encryption equipment.

Semi-encrypted silica fume is mainly composed of glassy SIO₂, and the particles are characterized by ultrafine powder. Most of the particle sizes are less than 1 um, and the average particle size is 0.1 um. It has a high specific surface area (300-400㎡/kg) and Volcanic ash activity.

After silica fume is mixed into cement concrete, it can well fill in the voids of cement particles, making the slurry more dense. In addition, it combines with free Ca(OH) to form stable calcium silicate hydrates ₂CaO and SIO₂ , H₂O, the gel strength of this hydrate is higher than that of Ca(OH) crystal, mainly manifested in:

(1) Increased strength. The compressive strength and flexural strength of concrete are greatly increased, and the compressive strength can be increased by 10-30%, and the flexural strength can be increased by more than 10%.

(2) Increase density. The impermeability is increased by 5-18 times, and the chemical resistance is increased by more than 4 times.

(3) Frost resistance: After 300-500 rapid freezing and thawing cycles, the relative elastic modulus of silica fume will decrease by 10-20%, while the relative elastic modulus of ordinary concrete will decrease by 30% after 25-50 cycles. — 73%.

(4) Early strength: Silica fume concrete shortens the induction period and has the characteristics of early strength.

(5) Anti-abrasion and cavitation erosion control: Compared with ordinary concrete, the anti-abrasion ability of silica powder concrete is 0.5-2.5 times higher, and the anti-cavitation ability is increased by 3-16 times.