Application Of Microsilica Fume in Shotcrete

The addition of silica fume to shotcrete can greatly improve the performance of dry-mix and wet-mix shotcrete. There are three types of silica fume; non-encrypted silica fume, encrypted low-density silica fume, and encrypted high-density silica fume. There is little difference in the performance of shotcrete made with these three different silica fumes.

Silica fume is a mineral admixture of high-grade pozzolan, mainly used to improve the strength and durability of concrete, and can replace Portland cement.

The use of silica fume was originally mainly in the United States, Canada and Scandinavia, and now it has been widely used all over the world. The performance of dry-mixed and wet-mixed shotcrete can be greatly improved by adding micro-silica fume, such as stability in rock mass. Applications in tunnel lining and foundation restoration. Excellent results can be obtained.

In the 1970s, Norway first used silica fume in sprayed concrete, which promoted the development of sprayed alkali tunnel lining. By the early 1980s, the use of microsilica in sprayed concrete had developed in the Western Hemisphere. First in western Canada and then in the United States Silica sprayed concrete has been used in various engineering projects: rock slope stabilization, tunnel linings for roads and railways, beams for road bridges. Restoration of columns and abutments, restoration of offshore works such as piles, revetments and quay support structures, restoration of chemical plants, artificial rock columns for zoos and sea aquariums, etc.

The use of silica fume can improve the performance and production technology of shotcrete as follows:

1 Reduce the springback of the shotcrete being mixed, thereby improving the economic benefits of the material.

2 The single-layer spray thickness on the top surface and vertical surface can be increased without coagulant, thereby improving production efficiency.

3 When repairing piles and revetments in tidal areas. Improves cohesion to resist washout.

4 Reduce the permeability and improve the freeze-thaw durability (note that the wet-mixed shotcrete must be properly air-entrained).

5 Both early and late flexural and compressive strengths were improved.

6 enhanced chloride. Nitrate. Resistance to chemical attack such as sulphate, acid and alkali aggregate reactions.

7. The high electrical resistivity and low permeability of micro-silica sprayed concrete in the project can reduce the corrosion of steel bars and wire mesh by chlorides.