Silica Fume is a by-product of ferrosilicon smelting, which is an essential mineral admixture to increase the strength in high-strength concrete, but at the same time, Silica Fume can also be mixed into foamed concrete to improve the performance of foamed concrete.
Foam concrete
Foam concrete, also known as bubble concrete, is a special variety of aerated concrete, its pore structure and material properties are close to aerated concrete, the difference between the two, only in the shape of the pores and aerated means.
Effect of Silica Fume on pore structure
With the increase of Silica Fume, the pore size of foamed concrete decreases continuously; when no Silica Fume is mixed, the pore size is mainly distributed in the range of 1.2 to 1.6ram, and the pores in this range account for 66% of the total pore ratio; when the amount of Silica Fume is increased to 9%, the pore size of foamed concrete is mainly distributed in the range of 0.9 to 1.2ram, and the pores in this range account for 69% of the total pore ratio. The pore size of foamed concrete is reduced from 1.39ram to 1.05ram when the amount of Silica Fume is increased from 0% to 9%; however, when the amount is more than 9%, the pore structure of foamed concrete does not change much, and the change in the pore size of the pores is extremely small.
Silica Fume as a kind of ultra-fine powder mixed into the foamed concrete mix, its particle size is relatively small, the specific surface area and water absorption rate is larger. With the increase of Silica Fume, due to the slurry consistency of foamed concrete gradually become larger, improve the cohesion between the slurry particles, so the surface tension of the bubble film in the slurry becomes larger, so that the bubble to overcome the surface tension of the liquid film and the slurry from the gravity of the need for greater internal pressure, when its peroxide content remains unchanged, the bubble pressure does not change, thus making the pore size of foamed concrete smaller; due to Silica Fume particle size is relatively small, in the foamed concrete slurry system not only play a role in filling capillary pores, and can occur with the cement hydration products of secondary hydration, the high alkaline hydration of calcium silicate into low alkaline hydration of calcium silicate, so that the foamed concrete pore wall densification; based on the above two reasons, the pore size of foamed concrete pores with the increase in the amount of micro-silica powder and reduce.
Effect of Silica Fume on mechanical properties
With the increase of microsilica powder, the strength of foamed concrete increases continuously, when the amount of micro-silica powder is 9%, the 28d compressive strength, flexural strength and vertical surface tensile strength increase by 5.6%, 1.8% and 26% respectively; micro-silica powder as ultra-fine powder mixed into foamed concrete, not only can fill the capillary structure in the pore wall of foamed concrete, and cement hydration products occur in the second hydration, will High alkaline hydrated calcium silicate into low alkaline hydrated calcium silicate, which makes the pore wall of foamed concrete dense, and makes the pore size of foamed concrete decreasing, more uniform distribution of pores, less likely to produce stress concentration when stressed, making the compressive strength, flexural strength and vertical surface tensile strength of foamed concrete increase with the increase of micro-silica powder admixture.
Precautions for mixing Silica Fume into foamed concrete
- The mixing time of foam concrete should be extended by 30 to 60 seconds after adding Silica Fume.
- Pay attention to control the dry shrinkage crack of micro-silica powder concrete, before the final setting after the foam concrete is poured, it must be sprayed to reduce water evaporation, or covered with plastic film, or sprayed with concrete curing agent to maintain the surface of concrete wet, but should not appear water flow and visible water drops.
- Silica Fume is very fine spherical particles, not suitable for dispersion, high viscosity.
Silica Fume can effectively improve the strength of concrete products no matter in which they are used, and its volcanic ash filling effect can also improve the pore structure of foamed concrete and enhance its performance.
Silica Fume Manufacturer
As a high-tech enterprise developing and producing various micro silica fume products, Henan Superior Abrasives Import & Export Co., Ltd produces high grade micro-silica powder which can fully meet the requirements of foamed concrete while meeting the national standards, if you need, you can leave a message on our website or call our customer phone for detailed consultation.
