Silica fume, also known as micro silica, is a by-product of the production of ferrosilicon or silicon(silicon metal) industrial. Silica fume is an amorphous silicon dioxide(SiO2) generated as...
Description of Silica Fume
Silica fume, also known as micro silica, is a by-product of the production of ferrosilicon or silicon(silicon metal) industrial. Silica fume is an amorphous silicon dioxide(SiO2) generated as a gas in submerged electrical arc furnaces during the reduction of quartz. The whole process needs to be recycled with a dust-removing protection facility.
The individual micro silica particles are extremely small, approximately 1/100th the size of an average cement particle. Due to its fine particles, large surface area, and high SiO2 content, silica fume is a very reactive pozzolan used in concrete. The quality of silica fume is specified by ASTM C 1240 and AASHTO M 307.
|Physical state||Ultrafine Amorphous Powder|
|Color||Light to dark gray|
|Solubility(Water)||Insoluble to slightly soluble|
|Melting point(℃)||Around 1230|
|Particle size(μm)||Around 0.3|
Specification of Silica Fume
|Loss on ignition||2||3||4||4||6|
（1）Very Stable Chemical and Physical Properties
（2）Increased compressive strength
（3）Reduced water permeability
（4）Increased Thermal Conductivity
（5）Improved abrasion resistance
Because of construction materials, silica fume can fill the pores between cement and concrete particles, form a gel with hydration products, and react with basic material magnesium oxide to form a gel.
Silica fume also can greatly improve the strength and density of concrete, Microsilica is widely used in refractory, concrete, industrial floor, dry powder mortar (or dry mixed mortar), grouting material, cementing wellhead, external wall insulation, and other industries.
The content of silica fume is generally 5% to 10% of cementitious material.
The mixing method of micro-silica is divided into internal mixing and external mixing.
(1) Internal admixture: under the premise of constant water consumption, 1 phr silica fume can replace 3-5 phr cement (weight) and keep the compressive strength of concrete unchanged, so as to improve other properties of concrete.
(2) External mixing: the strength and other properties of concrete can be significantly improved by adding silica fume. When concrete is mixed with silica fume, there is a certain slump loss. Silica fume must be combined with water reducing agent. It is suggested to mix fly ash and ground slag to improve its constructability.
(1) Input aggregate, then put silica fume and cement dry mix, then add water and other additives.
(2) Put coarse aggregate + 75% water + silica fume + 50% fine aggregate, stir for 15-30 seconds, then add cement + admixture + 50% fine aggregate + 25% water, and stir until uniform. The stirring time extends 20-25% or 50-60 seconds to ordinary concrete.
There is no significant difference between silica fume concrete and ordinary concrete in the construction method, but it is necessary to organize and vibrate compactly in construction. The early strength of silica fume concrete will make the final setting time advance, so attention should be paid to the plastering surface. At the same time, adding micro silica will improve the stickiness of concrete and greatly reduce bleeding, making the plastering surface slightly difficult.
Package of silica fume: Jump packages or customized packages are available on request.
Storage of silica fume: Dry storage. Avoid contact with moisture.
At present, the demand for Silica fumes in the international market is increasing. China plays an important role in the world in the production of ferrosilicon and silicon metal, the associated silicon fume is valued by foreign customers. Lots of foreign businessmen come to China to buy silicon fume.
China is the largest consumer of refractory materials, and the application technology of micro silica in refractory materials is relatively mature. From the development trend of refractory materials in China, due to the “Eleventh Five-Year Plan” period, metallurgy, building materials, and other industries will maintain steady development. The total demand for refractory materials is still large and will continue to maintain a rapid growth trend. The prospects of the silica fume are brightening.
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