Silica Fume
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Silica Fume is a byproduct of the production of silicon and ferrosilicon alloys. It is a very fine powder, with particles about 100 times smaller than cement particles.
Silica Fume is added to concrete mixtures as a pozzolanic material, which means it reacts with calcium hydroxide in the presence of water to form additional cementitious compounds that increase the strength and durability of concrete. Silica Fume works by filling in the spaces between cement particles, which helps increase the concrete’s density and strength. It also reacts with calcium hydroxide in the cement to form a gel-like material, which helps to strengthen the concrete further.
Silica Fume can be supplied in two forms: Densified and Undensified.
Densified Silica Fume is a Silica Fume that has been treated and compressed into very fine pellets. Densified Silica Fumes have a higher bulk density than Undensified Silica Fumes. Densified Silica Fume is often used in high-strength concrete applications, such as bridges, high-rise buildings, and marine structures. It is also used in applications requiring a low water-to-cement ratio, such as precast concrete. Densified Silica Fume can improve concrete’s compressive strength, tensile strength, and durability.
Undensified Silica Fume, on the other hand, is a loose powder that has not been treated or compressed. It has a lower bulk density than Densified Silica Fume and is less uniform in size and shape. Undensified Silica Fume is often used in applications where a high surface area is desired, such as in shotcrete or as an admixture in self-compacting concrete. It is also used in precast concrete, improving the surface finish and reducing the risk of cracking.