The influence of 8 characteristics of micro silica fume on the performance of grouting material

The influence of 8 characteristics of micro silica fume on the performance of grouting material

Silica fume will have many good effects on the performance of grouting materials. The beneficial effect of amorphous and very fine silica fume on high-performance grouts is manifested in both physical and chemical aspects: it acts as an ultra-fine filler; it acts as a crystal nucleus during early hydration and has high pozzolanic activity .

1. Accelerate the hydration of the cementitious material system. After replacing the cement with the same amount of silica fume, the 3d and 7d hydration heat release will increase greatly. The grouting project that needs to control the early hydration heat release should pay special attention to this when selecting materials a little.

2. Improve the strength of grouting material

When microsilica fume is used together with high-efficiency water reducer, microsilica fume and hydration product Ca(OH)2 react to form hydrated calcium silicate gel, which fills the gaps between cement particles and improves the interface structure and cohesive force. Form a dense structure, thereby significantly improving the strength of the grout. Generally, the dosage of micro-silica fume is 3%~8%, and the ultra-high-strength grouting material with a compressive strength of 100MPa can be prepared.

3. Increase density

Microsilica particles are very small and can fill the gaps between cement particles. The particles are densely packed, which can reduce bleeding, reduce capillary pores and average pore size. When the dosage of micro-silica fume is 3%~8%, good doping effect can be obtained. Water reducing agent should be used to ensure the dispersion of silica fume and cement.

4. Improve grouting material segregation and bleeding performance

5. Improve the impermeability and chemical corrosion resistance of grouting materials

6. The effect of micro-silica fume on the frost resistance of grouting materials

Regarding the effect of silica fume on the frost resistance of grouting materials, a large number of studies at home and abroad have shown that in the case of equivalent substitution, the frost resistance of grouting materials with an amount of less than 15% is basically the same, and sometimes it will increase (such as When the dosage is 3%~8%), but the dosage exceeds 20%, which will obviously reduce the frost resistance of the micro-silica fume grouting material.

In high-performance grouting materials, in order to reduce early plastic shrinkage and drying shrinkage, the amount of micro-silica fume is generally controlled within 10% of the total amount of cementitious materials. improve.

7. Microsilica fume and alkali-aggregate reaction

The alkali-aggregate reaction is the reaction between the active silica in the aggregate and the alkali in the cement to form a water-absorbing product, which increases in volume and causes expansion and cracking of the grouting material. When microsilica fume is added to the grout, the microsilica fume reacts with the alkali in the cement, which can prevent this excessive expansion. The practice at home and abroad shows that micro-silica fume is beneficial to inhibit the alkali-aggregate reaction in the grouting material. When calculating the total alkali content in the grouting material, the effective alkali content brought by micro-silica fume is calculated as 50% of the total alkali content.