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Micro-silica fume

  1. Silica Fume

The fine dust effused together with the exhaust gas in the process of the high temperature melting of industrial silicon and ferrosilicon is called silica fume or silicon powder. The content of SIO2 approximately accounts for 90% of the total amount of the flue gas, including 10% of SIO2 in free form. The surface-to-volume ratio is 28-35m2/g; it is of ash grey color with whiteness of  40-50. It appears carbon black if it is mixed with cement and caesious if it is mixed into concrete: with its minor granularity, the averge particle diameter is only 0.1-0.15 micrometer. The minimum particle diameter is only 0.01 micrometer. So it is often called micr-silicon powder. 

  1. Physical & chemical performance index
performance index Ms90 Ms85
Sio2 ≥90% ≥85%
Al2o3 ≤1.0% ≤1.0%
Fe2o3 ≤1.0% ≤1.0%
Cao ≤1.0% ≤1.0%
Mgo ≤1.5% ≤1.5%
Ignition loss ≤3.0% ≤6.0%
Water content ≤2.0% ≤2.0%
Activty index ≥90% ≥90%
Density uniformity ≤5% ≤5%
Fineness uniformity ≤5% ≤5%
  1. Silica Fume ̉s  function on improving the performmance of concrete
Investigation and research shows that the micro-silicon powder plays a positive role in improving concrete performance, especially in the follwing repects:
(1) The concrete intensity is obviously improved. Mixing some micr-silicon powder into the common concrete, we ̉ll find that the concrete intensity is improved by 40%-150% in accordance with the admixing mode (intemal or extemal admixing),the variety and the amount of filling material.
(2) The concrete ̉s placeability is obviously improved, with the micro-silicon powder, the concrete will not disintegrate or bleed, yet its slump constant is much less than that of common concrete. We can add high effciency water-reducing ageht as a compensation of the slump constant in practical use.
(3) The concrete mixed with micro-silicon powder is small hole (ultramicro-hole).its impermeability and frost resistance are much better than of  the common concrete. The test data show the concrete ̉s impermeability is enhanced by 6-11 times if it is mixed with 5%-10% micro-silicon powder in the form of internal admixing, the concrete ̉s frost resistance is enhanced by 2 times if the filler accounts for less than 15% of the total amount, wnich reaches the impermeability and frost resistance when the wanter-cement ratio of the common concrete is 0.4 .
(4) Other performmance is improved, for exosion resistance,impact resistance and so on.
(5) The rebound degree of the dry or wet blasting concrete is reduced, especially in wet blasting concrete when the rebound degree can be ignored.
  1. Application of micro-silicon powder
The micr-silicon powder is high-tech material with broad application prospect and it can be widely appliede to chemical industry and metallurgical industry. It can be used to improve the performance of cement or concrete and produce special concrete or compound cement with abrasive resistance, impact resistance, corrosion resistance, seepage control ability and frost resistance, which meets the special requirements in the well cementing of oil field, the drilling platform of the marine oil field, seaport and wharf, railroad bridge, expressway, runway,tunnel and high building engineering, it can also be used in rubber to improve its extensibility, tear resistance and tensile syrength, besides,it can cffectively improve the strength and durability of the fireproof materials and the cermic wares.
(1) the concrete mixed with micro-silicon powder helps to improve abrasion resistance of hydraulic and hydroelectric engineering sunch high molecular materials as epoxy resin mortar are often used as traditional abrasive-resistant materials. Although it is of high wearing capacity, as its linear expandability is several times of that of the common foundation concrete, it can hardly seamlessly seal with the foundation concrete and often crack and come off in natural climatic condition. What is more, the construction process is rather complicated with high cost and toxicity, thus it cannot be spread applied on a larg scale. However, the wearing capacity of the concrete mixed with micro-silicon powder is twice as much as that of common concrete. Its wearing capacity against 48m/s flow is improved by three times.
(2) The concrete mixed with micro-silicon powder helps to improve crack restance
 The concrete crack has aroused more and more peopli ̉s attention. In most circumstances, it is caused by the temperature rise in material ̉s hydration heat; for example, although the concrete admixed with fly ash can reduce the temperature rise, owning to its low early stength, it is not widely appliede.
(3) The concrete mixed with micro-silicon powder helps to improve its resistance to penetration and corrosion resistance and protect the rebar
 In underwater works, the chloride ion infiltrated into concrete will cause severe destructive effect, for example, the rebar gets rusted and the concrete delaminates with short service life. Norally, the tremie is used in the pouring of concrete underwater. The loss of cement mortar makes it hardly cohere with foundation and reduces the stenth of the water-concrete part. But the concrete admixed with micro-silicon powder can solve all these problems.
(4) Stong antiwear performance in the quick repair of road surface
It take 28 days for the road to be open to traffic if the common concrete is used. Even if the early stength concrete is used, it will take 3 days. The concrete road surface is inevitably destroyed. Traffic interruption often happens and cause severe economic loss if the regular repair method is used. However, if the early strength antiwear concrete mixed with micro-silicon powder is used ,it will achieve very good application effect. For example, for the airport runway, 80Mpa or over concrete with strong wearing capability is used.
(5) others:
1) Used in the production of water glass with its modulus greater than 4;
2) Used in the production of rubber stuffing. It enhances the rubber ̉s percentage of elongation, tear resistance and ageing resistance;
3) Used the production of high grade silica brick;
4) Used in pesticide and fertillzer and soil amendment. It can be used to produce potassium metasilicate by mixing with potassium hydroxide or potassium carbonate.
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