Densified Microsilica (Silica Fume) Grade 90D

Densified Microsilica with Minimum SiO2 Content 90%

Microsilica(silica fume) is a densified or undensified admixture which consists primirily fine amorphous SiO2 particles.Microsilica is used in construction, construction chemicals and refractory industries.

Principle of action

Microsilica fume/silica fume can be well filled in the voids of cement particles after being mixed into cement concrete, making the slurry more dense. In addition, it combines with free Ca(OH) to form a stable Calcium silicate hydrate 2CaO.SiO2.H2O, the gel strength of this hydrate is higher than that of Ca(OH) crystal.

Performance characteristics: Mixing an appropriate amount of microsilica powder into cement products and concrete admixtures can significantly improve the compression resistance, flexural resistance, anti-permeability, anti-corrosion, impact resistance and wear resistance at various stages, and significantly extend the service life. life and significantly improve product strength. Mainly manifested in:

1) Increase intensity. The compressive and flexural strength of concrete is greatly increased. By adding 5-10% of microsilica fume, the compressive strength can be increased by 10-30% and the flexural strength can be increased by more than 10%.
2) Increase density. The impermeability performance is increased by 5-18 times, and the chemical resistance is increased by more than 4 times.
3) Frost resistance: After 300-500 rapid freezing and thawing cycles of microsilica fume, the relative elastic modulus decreases by 10-20%, while the relative elastic modulus of ordinary concrete decreases by 30-50 times after 25-50 cycles. 73%.
4) Early strength: Microsilica fume concrete shortens the induction period and has early strength characteristics.
5) Resistance to abrasion and cavitation erosion: Microsilica fume concrete has an abrasion resistance that is 0.5-2.5 times higher than that of ordinary concrete, and a cavitation erosion resistance that is 3-16 times higher.

Specific application scope

1. Additives for refractory materials 

China is the world’s largest consumer of refractory materials. The application technology of XZH microsilica fume in refractory materials is relatively mature. In particular, high-quality microsilica fume has high fluidity, low water storage capacity, and high density. and high strength characteristics. It is mainly used as high-performance refractory castables, prefabricated parts, ladle materials, breathable bricks, self-flowing refractory castables and dry and wet spraying materials. As well as oxide-bonded silicon carbide products, high-temperature calcium silicate lightweight insulation materials, corundum-mullite push plates for electromagnetic kilns, high-temperature wear-resistant materials and products, corundum and ceramic products, etc. 

2. Used in high-strength concrete admixtures. 

The concrete industry is the field with the earliest research, the most achievements, and the widest application in the comprehensive utilization of microsilica fume abroad. Since microsilica fume has physical and chemical characteristics such as small particles, large specific surface area, high SiO2 purity, and strong volcanic ash activity, adding microsilica fume as an admixture to concrete can improve various properties of concrete, such as significantly improving plastic concrete. Adhesion performance and cohesion can greatly reduce the amount of rebound, increase the thickness of shotcrete in one shot, shorten the construction period, and save project costs. In the fields of ordinary high-performance concrete and ultra-high-performance reactive powder concrete, microsilica fume is used as an admixture to prepare high-strength concrete, and its strength level can reach hundreds of MPa or more. Such as: RPC concrete, HPC concrete, pipe pile concrete, etc. 

3. Mixed cement admixtures. 

In 1982, the mixed cement produced by the French Lafarge Cement Company using microsilica fume mixed with Portland clinker entered the market. Generally, spherical microsilica fume is ground together with clinker to produce mixed cement containing about 6% microsilica fume. At present, in some special fields of cement in China, microsilica fume has been widely added to mixed cement or special cement. 

4. The main material of the exterior wall insulation STP hollow insulation board 

utilizes the characteristics of XZH silica fume’s initial product density, low moisture, dryness, fineness, and good adhesion. The silica fume (and other auxiliary materials) are pressed against the wall The material is sealed in a certain size, area and shape. After sealing, it is compressed and drawn into a hollow state. As an inorganic non-metallic material, silica fume has a very low thermal conductivity, and the hollow insulation panels made of it are lighter, more energy-saving and have the characteristics of heat preservation. 

5. Commonly used additives such as mortar, grouting agent, and grouting materials.

Wall energy conservation, thermal insulation, and fire protection have been hot topics in the industry in recent years. Therefore, thermal insulation mortar, foamed concrete panels, and aerated concrete have all stood out. Silica fume is also clearly reflected in the application of these products in terms of improving strength and fluidity. At the same time, with the rapid development of high-speed rail technology and construction needs in recent years, through the improvement of grouting material technology, cement + fly ash + silica fume + cellulose + defoaming agent + water reducing agent + expansion agent, etc., have been developed into a super artesian. Sexy, high-strength, dense-pore grouting agent. This technology has become increasingly mature and has been widely used in highways, bridges, and high-speed rail fields.

6. In the chemical fertilizer industry

Potassium silicate, a slow-release agricultural fertilizer, can be made by mixing and heating microsilica powder with potassium hydroxide or potassium carbonate. It is not easy to volatilize and lose. It can protect the soil, promote crop root development, inhibit pests and diseases, and combine microsilica powder with potassium hydroxide or potassium carbonate. Waste materials such as waste bark produced by cellulose factories or wood factories are processed to form mixed substances that can enhance soil fertility and improve soil varieties.

Precautions for construction of microsilica powder

1) Due to the small particles of microsilica fume, large specific surface area, and high water demand, when microsilica fume is mixed into concrete, it must be used in conjunction with a high-efficiency water-reducing agent to achieve good results.

2) There are two ways to mix microsilica fume into concrete: internal mixing method and external mixing method. Since the internal mixing method reduces the amount of cement, it is generally used in medium and low-grade concrete; the external mixing method does not reduce the amount of cement and is generally used in high-grade concrete.

3) The dosage of microsilica fume in concrete should not be too high or too low. The general dosage is 5% to 10%. Within this range, the beneficial effect of microsilica fume is best exerted, that is, not only does microsilica fume replace cement, It is best to give full play to various excellent properties and avoid adverse effects, such as reduced frost resistance of concrete when the dosage is greater than 15%.

4) For impermeable concrete, seawater erosion-resistant concrete, and wear-resistant concrete, after adding microsilica fume, the water consumption will increase by approximately 20%, but the strength will remain unchanged.

5) Due to the high consistency of microsilica fume concrete, the slump of concrete should be designed to be 2~3cm larger than that of ordinary concrete.

6) The mixing time of microsilica fume concrete should be 0.5~2 minutes longer than that of ordinary concrete in order to mix the concrete more evenly and prevent microsilica fume from forming agglomerates in the concrete and causing quality accidents.

7) Secondary plastering: The concrete should be plastered twice before final setting. It is best to cover it after plastering to prevent surface cracks caused by rapid evaporation of water.

8) Moisturizing and curing: 2 hours to 4 hours after final setting, the concrete must be moisturized and cured, and it must be cured in a humid environment for more than 14 days. The curing method can be water-sprinkling moisturizing curing, covering moisturizing curing, or water storage curing.

Packaging

950/1000kg double plastic woven jumbo bag.

25kg woven bags with PE liner.

Special packaging can be supplied on request.