Silica Fumes For Concrete | Image Resource : image.slidesharecdn.com
 

Also known as micro silica, silica fume is a non-crystalline polymorph of silica and silicon dioxide. The EINECS number is 273-761-1 and CAS number is 69012-64-2. Being the by-product of ferrosilicon and silicon alloy production, it is a powder that is ultrafine. The average diameter of the spherical particles included in it are 150nm. It is mainly used as a pozzolanic material that is used in concretes for the purpose of high performance.
 
Due to the inherent rheological benefits in silica fumes, the concrete can be custom-tailored using placement methods. Certain modifying properties like creation of a high consistent workability, long distance concrete pumping or the fluid concrete ability to hold the slope. Silica fumes is one of the best concrete additives at the present.
 

People often misinterpret or confuse silica fumes with fumed silica despite of both of them having a very different CAS number. Fumed silica is known by another name, pyrogenic silica. The field of application, particle characteristics and production process of silica fume is completely different from fumed silica. Silica fume is used as a concrete additive and is an insert at the initial stage. The properties of this additive begin to show as soon as water starts to react with cement.
 
Two types of chemical compounds such as calcium silicate hydrate and calcium hydroxide are produced as the primary chemical reaction that takes place due to the mixture. Additional CHS is formed due to the pozzolanic reaction that takes place between the CH and silica fume in most of voids that are situated around the cement particles that are hydrated. The creation of additional CHS makes the concrete more flexural, with improved compressive and as well as bond-strength. Those void areas that are subjected to become a possible entrance to poisonous and deleterious materials also get a denser matrix.
 

Concrete additives are added for the purpose of inducing properties that are present in the admixtures but the silica fumes for concrete dramatically curtails the transportation of substances. Electrical currents and liquid compounds have a very diminished migration capability which results in high electrical resistivity and low permeability. The benefits of the inclusion of silica fumes in fresh concrete is evident even before any hardening process can begin.
 
The size of the silica fume particles extremely fine in comparison to an ordinary cement. This fine size helps in complementing the concrete finesse modulus with a ball-bearing like effect. The modification of concrete viscosity can improve the thixotropic behaviour. The silica fumes for concrete has a very high surface area which affects the water mobility that takes place within the concrete. This results in virtual elimination of bleeding and segregation of the concrete. The silica fumes that are included in the concrete can be easily purchased from whole sale or retail suppliers but the former type of seller will provide a more reasonable rate in comparison to what is provided by the latter.