- Make high strength concrete (above C70) with silica fume, which can significantly improve the strength and pumping performance of concrete;
- Make high impermeability (≥ P30), structural self-waterproof concrete, used in subways, tunnels, basements of high-rise buildings;
- Silica fume particle size distribution is reasonable, dense, hardness, good wear resistance, can significantly improve the curing of tensile, compressive, impact strength and wear resistance, impact resistance can be increased by 0.5-2.5 times.
- Silica fume can increase the thermal conductivity, change the adhesive and increase the flame retardant performance.
- It can reduce the exothermic peak temperature of epoxy resin curing reaction, reduce the linear expansion coefficient of the cured material and the shrinkage rate of the cured material, thus eliminating internal stress and preventing cracking.
- Because of the fine particle size and reasonable distribution of silica fume, it can effectively reduce and eliminate precipitation and delamination.
- Silica fume is pure, low impurity content, stable physical and chemical properties, so that the cured material has good insulating properties and anti-arc properties.
- The manufacture of marine and chemical concrete, due to its high dense properties, effectively prevent the penetration of sulfate and chloride ions on the concrete, erosion, to avoid corrosion of concrete reinforcement, thereby extending the life of concrete;
- The chemical composition of silica fume is silicon dioxide (SiO2), is an inert material, and most of the acids, alkalis do not have a chemical reaction, silica fume uniform distribution, covering the surface of the object, has a strong anti-corrosion, anti-cavitation ability increased by 3-16 times.
- Silica fume stacking density is small: one between 0.2-0.8, one between 1.0-2.2. As a polymer filling material, the dosage is less than other mineral fillers, the loading weight is small, saving polymer dosage, so it can reduce the cost of the product.
- Silica fume frost resistance: silica fume after 300-500 times rapid freeze-thaw cycle, the relative elastic modulus rung low 10-20%, while ordinary concrete through 25-50 cycles, the relative elastic modulus rung low 30-73%. Therefore, it can improve the frost resistance of concrete.
- Silica fume early strength: silica fume concrete makes the induction period shorten and has the characteristics of early strength. These characteristics are very good!
- Silica fume in water conservancy, highway, bridge projects, concrete not only needs the above basic indicators, but also has very harsh requirements for its wear resistance and scour resistance, it is very necessary to mix in silica fume;
- Silica fume is very active, with water-reducing properties, suitable for fast construction needs of early strength, high strength concrete admixture; tunnel, subway, large pit structure construction process for the support of high strength shotcrete admixture; underwater construction projects (such as: piers, dams, drilling platforms, etc.) with the admixture of concrete.
How much silica fume is added to concrete?
The amount of silica fume added to the concrete is generally 5-10% of the amount of cementitious materials.
The mixing method of micro silica fume is divided into internal and external mixing.
- Internal blending: under the premise of the same amount of water, 1 part of silica powder can replace 3-5 parts of cement (weight) and maintain the same compressive strength of concrete and improve the other properties of concrete.
- External blending: the amount of cement remains unchanged, the addition of micro silica fume significantly improve the strength of concrete and other properties. Concrete mixed with micro-silica powder when there is a certain slump loss. This point needs to be noted in the ratio test.
Micro silica fume must be used in conjunction with water reducing agents, it is recommended to compound fly ash and finely ground slag to improve its constructability.
When preparing concrete with micro silica fume, the general weight ratio with cementitious materials are.
(1) High-performance concrete: 5-10%.
(2) hydraulic concrete: 5-10%.
(3) Shotcrete: 5-10%.
(4) Pumping aid: 2-3%.
(5) wear-resistant industrial flooring: 6-8%.
(6) polymer mortar, insulation mortar: 10-15%.
(7) Indefinite refractory castables: 6-8%. Before use, please select the reasonable and economic dosing amount through experiment according to the actual needs.
Silica Fume Mixing method
Micro-silica powder concrete and castable should be made by the test room. Strictly follow the construction ratio. In the mixing of micro-silica powder concrete, the micro-silica powder should be added to the mixer immediately after the aggregate is fed. There are two procedures for adding.
(1) put in the aggregate, followed by micro-silica powder, cement dry mix, and then add water and other additives.
(2) Put in coarse aggregate + 75% water + silica fume + 50% fine aggregate, mix for 15-30 seconds, then put in cement + admixture + 50% fine aggregate + 25% water, mix until uniform. Mixing time is 20-25% or 50-60 seconds longer than ordinary concrete. Never add silica powder into the already mixed concrete.
Silica Fume Construction method
There is no significant difference between the construction method of micro-silica powder concrete and ordinary concrete, but it is necessary to organize well and vibrate densely during construction. The early strength of micro-silica concrete will make the final setting time earlier, which should be paid attention to when plastering; at the same time, the addition of micro-silica powder will improve the stickiness of concrete and significantly reduce water secretion, making plastering slightly difficult.
Silica Fume Construction safety
Micro silica fume concrete construction safety should be strictly in accordance with the relevant national construction specifications for concrete projects, but because the micro-silica powder is light, it is strictly prohibited to throw the material from above to prevent the micro silica fume from flying.
