The principle of Ewende micro silica powder (silica fume) to improve the frost resistance of concrete mainly has the following aspects:
- Optimization of microstructure
Dense filling：silica fume particles are extremely fine, can be fully filled into the pores of concrete, so that the concrete structure is more dense. Reduced porosity within the concrete reduces the space for water infiltration and icing, thus reducing the damage to the concrete caused by freeze-thaw cycles.
For example, during the concrete mixing process, the microsilica powder can be evenly dispersed in the cement paste, filling in the voids between the cement particles and making the overall structure of concrete more compact.
- Promote the hydration reaction of cement
Silica fume can react with calcium hydroxide produced by cement hydration to produce more calcium silicate gel. The calcium silicate gel can further fill the pores and improve the strength and compactness of concrete.
This reaction not only makes the concrete more dense, but also consumes part of the calcium hydroxide that is unfavorable to the frost resistance of the concrete, reducing the risk of deterioration of the concrete in the freeze-thaw environment.
- Enhancement of mechanical properties
Strength improvement:the addition of microsilica powder can significantly improve the compressive, tensile and flexural strength of concrete. Concrete with high strength is better able to resist damage due to ice expansion pressure during freeze-thaw cycles.
For example, the internal structure of concrete modified with microsilica fume can better maintain its integrity when subjected to freeze-thaw cycles, reducing the occurrence and expansion of cracks.
Improved toughness: Silica fume can improve the toughness of concrete, so that it is less prone to brittle damage in the freeze-thaw cycle. The improvement of toughness enables concrete to better adapt to the volume change during freeze-thaw process and reduce cracks caused by stress concentration.
For example, in the freeze-thaw environment, concrete with better toughness can better absorb and disperse the ice expansion pressure, reducing the degree of destruction of concrete.
- Reduce permeability
Reduce capillary channels: Microsilica powder fills the capillary pore channels in concrete and reduces the permeability of concrete. This makes it difficult for moisture to enter the interior of the concrete, reducing the possibility of freeze-thaw damage.
For example, low permeability concrete is better able to prevent moisture penetration and freezing during freeze-thaw cycles, thus improving the frost resistance of concrete.
Improved resistance to chloride penetration: Micro silica powder can improve concrete’s resistance to chloride ion penetration and reduce chloride ion corrosion of steel reinforcement. Corrosion of steel reinforcement can lead to the destruction of the concrete structure and reduce the frost resistance of concrete.
For example, in areas with high chloride ion content such as marine environments, concrete improved with microsilica powder can better protect the steel reinforcement, extend the service life of the concrete structure and improve its frost resistance.