1.Accelerate the hydration of the cementitious material system this process.
After mixing with micro silica powder partially replacing cement in equal quantities, the amount of heat of hydration release increases dramatically in 3 days and 7 days. For grouting projects that require control of early hydration heat release, special attention should be paid to this point when selecting materials.
The effect of micro silica powder on the release of heat of hydration of the cementitious material system
2.Improve the strength of grouting materials.
When micro-silica powder and high-efficiency water reducing agent are used together, the silica powder reacts with the hydration product calcium hydroxide to generate hydrated calcium silicate gel, which fills the gaps between cement particles, improves the interfacial structure and adhesion, and forms a dense structure, which significantly improves the strength of the grouting material. In general, when the silica fume content is 3%~8%, the ultra-high strength grouting material with a compressive strength of 100 MPa can be prepared.
3.Increase compactness
The particles of micro silica powder are very fine and can fill the voids between cement particles. The dense accumulation of particles can reduce bleeding and capillary pores as well as the average pore size. Good mixing results can be obtained when the silica fume content is 3% to 8%. Water reducer should be used to ensure the dispersion of silica fume and cement.
4.Improve the segregation and water secretion properties of grouting materials
5.Improve the impermeability and chemical resistance of grouting materials
6.The effect of microsilica powder on the frost resistance of grouting materials
On the effect of micro silica powder on the frost resistance of grouting materials, a large number of studies at home and abroad have shown that, under the same replacement conditions, the dosage of less than 15% of the grouting material frost resistance is basically the same, and sometimes improved (such as the dosage of 3% to 8%), but the dosage of more than 20% of the grouting material frost resistance will be significantly reduced.
In high-performance grouting materials, taking into account the reduction of early plastic shrinkage and dry shrinkage, the content of silica fume is generally controlled within 10% of the total amount of cementitious materials. At this time, frost resistance is usually improved due to the reduction of bubble spacing coefficient.
7.Reaction between microsilica powder and alkali aggregate
Alkali-aggregate reaction is the active silica in the aggregate reacts with the alkali in the cement to generate water absorption products, which increase in volume and lead to expansion and cracking of the grouting material. When the micro silica powder is mixed into the grout material, the micro silica powder reacts with the alkali in the cement to prevent this over-expansion. Domestic and international practice shows that micro silica powder is beneficial to inhibit the alkali aggregate reaction in grouting materials. When calculating the total alkali content in grouting materials, the effective alkali content brought in by micro silica powder is calculated as 50% of the total alkali content.