Why is microsilica added to concrete?

Microsilica is used to produce high-strength concrete (above C70), significantly enhancing the strength and pumpability of concrete.

It is used to create high-impermeability (≥ P30) and structurally self-waterproof concrete for subways, tunnels, and basements of high-rise buildings.

Microsilica has a reasonable particle size distribution, high density, and excellent hardness, providing superior wear resistance. It can greatly improve the tensile strength, compressive strength, impact resistance, and wear resistance of cured materials, increasing abrasion resistance by 0.5 to 2.5 times.

Microsilica can increase thermal conductivity, improve adhesive properties, and enhance flame retardancy.

It reduces the exothermic peak temperature of epoxy resin curing reactions, decreases the linear expansion coefficient and shrinkage of cured materials, thereby eliminating internal stress and preventing cracking.

Due to its fine particle size and reasonable distribution, microsilica effectively reduces or eliminates sedimentation and stratification.

Microsilica is of high purity, with low impurity content and stable physicochemical properties, giving cured materials excellent insulation and arc resistance.

It is used in marine and chemical-resistant concrete. Its high density effectively prevents sulfate and chloride ion penetration and erosion, protecting reinforcement from corrosion and extending the service life of concrete.

The chemical composition of microsilica is silicon dioxide (SiO₂), an inert substance that does not react with most acids and alkalis. When evenly distributed and covering the surface of objects, it provides strong corrosion resistance, increasing cavitation erosion resistance by 3 to 16 times.

Microsilica has a low bulk density, ranging from 0.2–0.8 or 1.0–2.2. As a polymer filler, it requires less material compared to other mineral fillers, reduces loading weight, saves polymer usage, and thus lowers production costs.

Frost resistance: After 300–500 rapid freeze-thaw cycles, the relative elastic modulus of microsilica concrete decreases by only 10–20%, whereas ordinary concrete decreases by 30–73% after 25–50 cycles. This significantly improves the frost resistance of concrete.

Early strength: Microsilica concrete shortens the induction period, providing early strength characteristics. These properties are highly advantageous.

In water conservancy, highway, and bridge projects, concrete not only requires the basic performance indicators but also demands exceptional wear and erosion resistance. Adding microsilica is essential in such cases.

Microsilica’s high reactivity provides water-reducing properties, making it suitable as an admixture for early-strength and high-strength concrete needed in fast-track construction; for high-strength shotcrete used in tunnel, subway, and large foundation pit support; and for concrete in underwater projects (such as bridge piers, dams, and drilling platforms).