Is silica fume an admixture in concrete?
Is silica fume an admixture in concrete?
Silica fume is a byproduct of producing silicon metal or ferrosilicon alloys. One of the most beneficial uses for silica fume is in concrete. Perhaps the most important use of this material is as a mineral admixture in concrete. Silica fume consists primarily of amorphous (non-crystalline) silicon dioxide (SiO2).
How does silica fume effect concrete?
Silica fume is added to Portland cement concrete to improve its properties, in particular its compressive strength, bond strength, and abrasion resistance. Silica fume also blocks the pores in the fresh concrete so water within the concrete is not allowed to come to the surface.
What is silica fume in construction?
Silica fume, a by-product of the ferrosilicon industry, is a highly pozzolanic material that is used to enhance mechanical and durability properties of concrete. It may be added directly to concrete as an individual ingredient or in a blend of portland cement and silica fume.
How does silica fume improve concrete strength?
The resistance against chloride ion penetration increased with the increase in the contents of silica fume in concrete. A reduction in water-binder ratio (from 0.35 to 0.30) increased the ability of the concrete to resist chloride ion’s penetration.
What are the disadvantages of high silica cement?
disadvantages of silica fume in concrete
- Silica fume concrete is too viscous and difficult to apply.it is not easy to wipe the surface.
- Silica fume requires a high amount of water and needs to be used with a superplasticizer.
- The price of silica fume is relatively high compared to cement and fly ash.
What are the properties of silica fume?
Various properties of silica fume cocnrete, including slump, air-content, compressive strength, flexural strength, permeability, and permeable void volume were investigated, and the effect of the silica fume replacement ratio of cement is described.
Is silica still used in concrete?
Crystalline silica is a common mineral found in the earth’s crust. Materials like sand, stone, concrete, and mortar contain crystalline silica. It is also used to make products such as glass, pottery, ceramics, bricks, and artificial stone. About 2.3 million people in the U.S. are exposed to silica at work.
What is silica fume and how is it produced?
Silica fume is a by-product from the production of elemental silicon or alloys containing silicon in electric arc furnaces. At a temperature of approximately 2000°C the reduction of high-purity quartz to silicon produces silicon dioxide vapor, which oxidizes and condenses at low temperatures to produce silica fume.
Why is silica fume a good pozzolan?
Silica fume is a pozzolanic material composed of extremely fine, amorphous spheres produced as a byproduct in the manufacture of silicon metals. It has a high water demand and it is more reactive than natural pozzolan or fly ash. It increases the compressive strength significantly.
Why is microsilica used in concrete?
Microsilica or silica fume is an excellent admixture for concrete as it leads to better engineering properties. It reduces thermal cracking, improves durability, and increases strength. There are a number of construction applications in which silica fume has been used successfully.
What are the advantages of using fly ash in concrete?
Fly Ash has very small particles which makes the concrete highly dense and reduces the permeability of concrete. It can add greater strength to the building. The concrete mixture generates a very low heat of hydration which prevents thermal cracking. Fly Ash concrete is resistant to acid and sulphate attacks.
How much silica does it take to get silicosis?
Because silicosis is caused by cumulative or repeated exposure to respirable crystalline silica, it makes sense that we would want to limit exposure as much as possible! OSHA has set the Personal Exposure Limit (PEL) at 50 micrograms per cubic meter of air, averaged over an 8 hour shift.
What kind of concrete is silica fume concrete?
SILICA FUME CONCRETE Silica fume is an artificial pozzolona having high pozzolonic activity. It is a By- product from an electric arc furnace used in manufacture of silicon metal or silicon alloy. It has high silica content of more than 80%. It is an excellent for use as a portland cement supplement. 4. SILICA FUME CONCRETE 5.
How is silicon dioxide used in concrete admixture?
Perhaps the most important use of this material is as a mineral admixture in concrete. Silica fume consists primarily of amorphous (non-crystalline) silicon dioxide (SiO2). The individual particles are extremely small, approximately 1/100th the size of an average cement particle.
Which is the best quality of silica fume?
The quality of silica fume is specified by ASTM C 1240 and AASHTO M 307. High-strength concrete is a very economical material for carrying vertical loads in high-rise structures. Until a few years ago, 6,000 psi concrete was considered to be high strength.
Which is a byproduct of Portland cement hydration?
Silica fume (SF) is an industrial byproduct mainly from ferrosilicon producing companies. Condensed silica fume is a very fine, amorphous, and reactive mineral admixture. It reacts readily with the calcium hydroxide, which is produced during Portland cement hydration.