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Micro silica Physicochemical Properties:

1, Micro silica appearance: white&#;Refractoriness > &#;&#; Bulk density: 200 to 250 kg / m3.

2, Micro silica fineness: 90% fineness of 0.1μm; average particle size of 0.1 &#; 0.2μm, specific surface area: 20 &#; 28 m2 / g. Micro silica fineness and specific surface area is 80 to 100 times of that of cement, 50 to 70 times of fly ash.

3, Micro silica particle morphology and mineralogical structure: Due to the surface tension of the phase change, micro silica fume forms into amorphous phase amorphous spherical particles with smooth surface, or a plurality of ball particles stick together.

Micro silica fume is a high activity pozzolanic material with large surface area. Micro silica in materials will play the role of lubrication with the tiny spherical body.

Silica Fume has a stable pH and a low impurity level and is perfectly adapted to the requirements of refractory castables. Its use improves the flow, mechanical properties (especially hot strength), and durability (via permeability reduction).

Silica fume in refractory castables provides better particle packing. Silica fume use requires less water, while maintaining the same flow characteristics. Silica fume use also promotes low temperature sintering, and the formation of mullite in the matrix of castables. This allows production of castables which have a low permeability to gas, slag and metal penetration. Castables made with silica fume are stronger than non-silica fume castables, especially at high temperatures and higher density. Silica fume use will attain lower porosity and are more volume stable.

Acting as a filler is not the only effect of microsilica in refractory castables. It has been shown in studies of cement pastes with microsilica that a certain fraction of the microsilica reacts with the cement and water to form so-called C-A-S-H (CaO-Al2O3-SiO2-H2O) phases in addition to the C-A-H (CaO-Al2O3-H2O) and A-H (CaO-Al2O3) phases normally found in hydrated cement. The C-A-S-H phases are of zeolitic nature and the amounts of these hydration products are dependent on the quality (purity) of the microsilica.

1. After adding aggregate, add micro silica and cement without delay, then add water and other admixtures.
2. Add coarse aggregate + 75% water + micro silica + 50% fine aggregate, and stirred for 15-30 seconds, then put cement + additive + 50% fine aggregate + 25% water and stirred. Stirring time is 20-25% longer than that of ordinary cement or 50-60. Avoid put the silicon powder to the already mixed concrete.

Micro-silica fume is widely used in the refractory industries:

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1.Instead of pure aluminum oxide mud as refractory material.

2.As the additive for production of amorphous and shaped refractory products, to improve the strength, and high temperature performance.

3.Other refractory products like cohesive agent, bonding agent, accelerator and additives.

the applications of silica fume in refractory materials

Silica fume is mainly used to improve refractory materials for over forty years. Silica fume using in refractory materials has many features as following:

• Silica fume can increase the liquidity of pouring type of refractory materials, reduce water consumption and make it easy to shape and improve production efficiency greatly.
• Because of its ultra-structure of filler, the density of refractory material and strength will increase significantly;
• Silica fume has high activity, under the premise of existence of Al2O3 ingredients, it is easy to generate the mullite phase to make the high temperature strength and thermal shock resistance increase greatly.
• Silica fume has strong hydrophilic. Adding water, it can make stronger cohesion in refractory material in order to improve the performance of high temperature resistance of refractory and prolong the service life of refractory products.

Refractory material usually uses unencrypted micro silicon powder. At present, besides in casting refractory material widely using, unencrypted micro silicon is applied extensively in the fused and sintered refractories. Such as low cement castable, developed in the seventy&#;s, is a new type of high performance refractory castable, which is successfully developed by France first. Therefore, silica fume is widely applied in various industrial high temperature furnace with good technical and economic effect.

Low cement castable and ordinary castable both use calcium aluminate cement. But adding silica fume and high efficiency water reducing agent, it can not only save expensive aluminate cement 50-70% but also improve the cement performance. Silica fume has double applications in the new castable. Because of the size of silica fume is very small, and an important feature of silica fume can reduce the cement content in the refractory casting material.

Silica fume is widely used in refractory industry. Refractory raw material can be instead of pure aluminium oxide mud as refractor material; Used as an additive to join in the production of amorphous and shaped refractory products, silica fume can improve strength and increase the high temperature performance. In addition, it is applied in the ladle as a whole as condensation agent. According to the data indicate, the low cement castable with silica fume has been widely applied in coke oven, the sintering, steel-making, steel rolling, nonferrous metallurgy, petroleum as well as chemical, cement, glass ceramics and power generation industry etc at home and abroad. More info about silica fume applications, you can browse our website: www.sialloy.com Anyang Huatuo Metallurgy Co.,LTD will provide detailed introduction for our customers.

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