Silica fume or micro silica is an amorphous polymorph of silicon dioxide and silica.
Silica fume is an ultrafine powder. It is a silicon and ferrosilicon alloy. Micro silica consists of spherical particles with an average particle diameter of 150 nm. It is a very reactive pozzolana due to its chemical and physical properties.
When silica fume is used in cementitious applications, silica fume works as both a filler – improving the physical structure by taking the spaces between the cement particles – and as a “pozzolan” reacting chemically to impart far higher strength and durability to concrete.
Silica fume is a byproduct of creating silicon metal or ferrosilicon alloys. One of the most valuable uses for silica fume is in concrete. Due to its chemical & physical characteristics, it is chemical responsive. Concrete containing silica fume can have extremely high strength and can be truly tough. Silica fume is accessible from suppliers of concrete admixtures and, when specified, is simply added during concrete production. Placing, finishing, and curing silica-fume concrete require special attention on the part of the concrete contractor.
Silica fume comprises fundamentally of undefined (non-glasslike) silicon dioxide (SiO2). The singular particles are minuscule, roughly 1/100th the size of a normal concrete molecule. On account of its fine particles, huge surface region, and high SiO2 content, silica fume is an exceptionally receptive pozzolan when utilized in concrete. The nature of silica fume is indicated by ASTM C 1240 and AASHTO M 307.
High-strength concrete is an extremely affordable material for conveying vertical burdens in tall building structures. Until a couple of years prior, 6,000 psi concrete was viewed as high strength. Today, utilizing silica fume, concrete with compressive strength of more than 15,000 psi can be promptly delivered. The construction is displayed at the above right utilized silica-fume concrete with a predetermined compressive strength of 12,000 psi in segments coming to starting from the earliest stage the 57th story.
The best reason for substantial disintegration in the US today is consumption instigated by deicing or marine salts. Silica-fume concrete with low water content is exceptionally impervious to the entrance by chloride particles. Increasingly more transportation organizations are utilizing silica fume in their substantial for the development of new extensions or recovery of existing designs.
Silica-fume concrete doesn’t simply occur. A specifier should settle on a cognizant choice to remember it for cement to accomplish wanted substantial properties. Help with determining silica-fume concrete for high strength or expanded solidness can be acquired from the SFA or from significant admixture providers.
Silica fume for use in concrete is accessible in wet or dry structures. It is typically added during substantial creation at a substantial plant as displayed in the photograph. Silica fume concrete has been effectively delivered in both focal blend and dry-cluster plants. Help is promptly accessible on all parts of dealing with silica fume and utilizing it to create predictable, excellent cement.
Silica-fume cement ought to be shipped, put, got done, and restored following the great cementing rehearses illustrated by the American Concrete Institute. Flatwork containing silica fume concrete for the most part requires less completing exertion than ordinary cement. The photograph shows the “one-pass” completing the cycle in which the silica-fume concrete is put, united, and finished with practically zero holding up time between activities. To acquire the most advantages from utilizing silica fume, the substance should be relieved successfully. The SFA or your substantial provider can give any vital help concerning development tasks.
Properties of Silica Fume:
- The particle size of silica fume is less than 1 micrometer.
- Silica fume is 100 times smaller than the average cement particle.
- Bulk density varies from 130 to 600 kg/m3.
- The specific gravity of silica fume varies from 2.2 to 2.3.
- The specific surface area of silica fume ranges from 15,000 to 30,000 m2/kg
Advantages of Silica Fume:
- It provides high compressive strength.
- Silica fume gives high flexural strength.
- Silica fume is the value of modulus of elasticity.
- It enhances the overall durability of the concrete.
- Micro silica increases the permeability of concrete to water.