What is the difference between fumed silica and silica?

Dear Hadi Maghsoudiganjeh , fumed silica is produced in a flame or torch, SiO2 molecules coalesce and form silica nanoparticles that aggregate in a chain shaped structure. On the other hand, silica nanoparticles made by sol-gel or other methods are isolated particles.

Why do we use silica fume in concrete?

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. Silica addition refines pore structure and produces concrete of improved mechanical strength.

How do you make silica fume?

Fumed silica is made from flame pyrolysis of silicon tetrachloride or from quartz sand vaporized in a 3000 °C electric arc.

What is fumed silica powder?

Fumed silica serves as a universal thickening agent, a thickener in milkshakes, and a anticaking agent in powdered foods. Like silica gel, it serves as a desiccant. It is used in cosmetics for its light-diffusing properties. It is used as a light abrasive, in products like toothpaste.

Is silica fume a hydraulic material?

Supplementary cementing materials (SCMs) contribute to the properties of hardened concrete through hydraulic or pozzolanic activity. Typical examples are fly ashes, slag cement (ground, granulated blast-furnace slag), and silica fume. Slag cement is hydraulic and can be added to cement as an SCM.

Is silica fume expensive?

Condensed silica fume costs from $400-$1,000/ton, which is significantly higher than portland cement ($90/ton).

What is Ggbs material?

GGBS (Ground Granulated Blast-furnace Slag) is a cementitious material whose main use is in concrete and is a by-product from the blast-furnaces used to make iron. This ‘granulated’ slag is then dried and ground to a fine powder.

How is precipitated silica made?

Precipitated silica is produced by the controlled neutralization of dilute sodium silicate (waterglass) by either concentrated sulfuric, hydrochloric, or carbonic acids. The raw materials are those required for the silicate: sand, soda ash, caustic soda, and water.

What is the difference between precipitated and fumed silica?

While fumed silica is often used as a matting agent by conservators, its efficacy has been called into question. Fumed silica is produced commercially as a thickening or thixotropic agent, not as a matting agent; in contrast, precipitated silica is sold specifically as a matting agent.

How do you make fumed silica?

Fumed silica is synthesized by the pyrolysis method in which silicon tetrachloride reacts with oxygen in a flame, and the SiO2 seed grows in size or aggregates [8].

What is silica fume?

Silica fume, also known as microsilica, is a fine-grain, thin, and very high surface area silica. The particle size of silica fume is around 1/100th the size of an average cement particle.

What is the difference between silica and crystalline silica?

The difference between the two is at the atomic level. Crystalline silica (quartz) is the form of silica that OSHA is writing the new regulations to cover, it is a health hazard. It is not reactive with portland cement, meaning it does not cause ASR (alkali-silica reactivity) regardless of particle size.

What is the particle size of fumed silica?

Fumed silica normally classified into two classes: treated and untreated(also known as hydrophilic and hydrophobic). Normally the hydrophilic one is cheaper than hydrophobic. The particle size of fumed silica is around 7~40 nm.

What is the difference between silica fume and fly ash?

Difference between Silica Fume and Fly Ash – Scribd Silica Fume is typically much more reactive, particularly at early ages , because of its higher silicon dioxide content and because of its very small particle size .