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The manufacturer analyzes the filling effect application principle of silica fume in detail

silica fume concrete

Silica fume, also known as Condensed Silica Fume, is produced by ferroalloys when smelting ferrosilicon and industrial silicon, and a large amount of highly volatile SiO2 and Si gas is produced in the mineral-heated electric furnace, which is precipitated by rapid oxidation and condensation with air after the gas is discharged. Silica fume mixed into concrete has a good filling effect. So, what is the application principle of the filling effect of silica fume?

Improve the fluidity

Concrete in the composition of silica fume mixed compound, in order to obtain the construction requirements of the liquidity, often need to add more water (more than the amount of water required for cement hydration), these extra water not only makes the cement slurry thinner, weakening the cementitious force, and excess water residue in the concrete to form a blister or waterway, with the concrete hardening and evaporation will leave pores. Thinner water-based slurry, excess water will be residual evaporation formed in the concrete, with the cured concrete blisters or waterways to leave holes. Thus reducing the actual stress area of concrete, and in the mix when stressed, easy to produce stress concentrations around the pores.

Increase the strength

Some scholars have calculated: 15% of silica fume instead of cement, the number of cement particles and the number of silica fume particles in the ratio of 1 : 2000000, that is, two million silica fume to a cement particle, so silica fume has a great impact on the strength of high-performance concrete. In high performance concrete less than 100 times the diameter of the cement particles of silica fume, filled between the pores of the cement paste, filled between the voids of cement particles, the effect as cement particles filled between the voids of the aggregate and fine aggregate filled between the voids of coarse aggregate, from the microscopic scale to increase the density of high performance concrete, improve the strength of high performance concrete, this is the silica fume “filling effect”. In high performance concrete, the silica fume filled in the cement paste makes the number of cement paste pores significantly reduced and the homogeneity increased, while the total void ratio remains basically unchanged. High-performance concrete due to a certain amount of silica fume, its strength compared with ordinary concrete (without silica fume), there is a significant improvement.

Reduce water secretion

Silica fume in the transition zone of the interface between cement paste and aggregate reduces the water secretion of high-performance concrete, prevents the aggregation of water under the aggregate, makes the microstructure of the transition zone of the aggregate interface similar to that of the cement paste, thus improving the denseness of the interface filtration zone and effectively reducing the thickness of the interface transition zone. The silica fume particles become the “seed” of Ca(OH)2, which makes the Ca(OH)2 crystal size smaller and orientation more random. Therefore, the addition of silica fume improves the bond strength between cement paste and aggregate in high performance concrete, eliminates the “weak connection” problem of different composite components in concrete, and makes high performance concrete have the characteristics of composite materials. The aggregate particles play a reinforcing role in high performance concrete, not just as inert fillers. Silica fume has little effect on the strength of the cement paste, but can make the concrete with the same water-cement ratio significantly stronger than the matrix.

Silica fume incorporated into concrete should also be mixed according to the conditions of application of silica fume in cement paste in order to effectively improve the use of cement paste and concrete and increase the strength and durability of concrete.

HSA Silica fume

HSA has been a global supplier of high-quality silica fume since 2001. We have established long-term and stable cooperation with many concrete construction companies around the world to provide our customers with high-quality silica fume with different contents and different uses, fully satisfying all kinds of concrete project needs.

If you have any needs for silica fume, please feel free to contact us!

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