Analysis Of The Reasons Why Micro-Silica Fume Will Be Widely Used

Micro-silica fume has a good filling effect and has been widely used in construction concrete. Why?

When concrete is mixing sand and gravel, in order to obtain the fluidity required by concrete construction, it is often necessary to add more water (more than the amount of water required for cement hydration). This additional water not only makes the cement slurry thinner, weakens the cementing force, but also excess water Remains in the concrete to form blisters or water channels, leaving a large number of pores after the concrete hardens and evaporates, thereby reducing the actual force area of the concrete, and when the concrete is stressed, stress concentration is likely to occur around the pores.

In concrete, the internal bleeding is blocked by aggregate particles and gathers under the aggregate to form a porous interface. More Ca(OH)2 is formed in the filtration area of the aggregate interface than in other areas. The Ca(OH)2 crystal grows larger and has a strong orientation parallel to the surface of the aggregate. The large Ca(OH)2 crystal parallel to the surface of the aggregate is easier to crack, which is better than calcium silicate hydrate gel (CSH) weak. The interface filter zone between cement slurry and aggregate becomes the weakened area of concrete due to its porous and large Ca(OH)2 crystals arranged in orientation. Due to the addition of a certain amount of micro-silica fume in HPC, its strength is significantly improved compared with ordinary concrete (without silica fume).

We have obtained a lot of detailed data through experiments: If 15% of the micro-silica fume is used to replace the cement, the ratio of the number of cement particles to the number of micro-silica particles is 1:2000000, that is, two million micro-silica particles per cement particle , So the micro-silica fume has a great influence on the strength of HPC. In HPC, microsilica powder, which is less than 100 times the diameter of the cement particles, is filled in the pores of the cement paste and filled in the voids of the cement particles. The effect is the same as that of the cement particles filling the gaps in the aggregate and the fine aggregate filling the coarse The same between the gaps of the aggregate, increase the compactness of HPC from the microscopic scale and increase the strength of HPC, which is the "filling effect" of micro-silica powder. In HPC, the micro-silica fume filled in the cement paste significantly reduces the number of pores of the cement paste, improves the homogeneity, and keeps the total porosity basically unchanged.

The silica fume in the transition zone of cement slurry and aggregate interface reduces the bleeding of HPC and prevents moisture from accumulating under the aggregate, making the transition zone of aggregate interface similar to the microstructure of cement paste, thereby improving the filtration zone of the interface. Compactness and effectively reduce the thickness of the interface transition zone. The micro-silica particles become the "seeds" of Ca(OH)2, making the size of Ca(OH)2 crystals smaller and the orientation more random. Therefore, the addition of silica fume not only improves the bonding strength of cement paste and aggregate in HPC, but also eliminates the "weak connection" problem of different composite components in concrete, making HPC have the characteristics of composite materials. Particles play a reinforcing role in HPC, not just inert fillers. Micro-silica fume does not greatly affect the strength of cement paste (no aggregate), but it can increase the strength of concrete with the same water-binder ratio. It is significantly higher than the strength of its matrix (clean pulp).

　　 Through detailed understanding of the overall structure of concrete, we now understand. It is not difficult to understand that micro-silica fume has such a good filling effect that it is widely used in construction concrete. Concrete microsilica is really an indispensable new material in the modern construction concrete industry.