Understanding the Difference Between Colloidal Silica, Potassium Silicate and Sodium Silicate
Silica is a naturally occurring mineral commonly found in sand, rocks, and soil. It is composed of silicon and oxygen atoms and has various industrial applications due to its unique properties. When mixed with water, silica can form colloidal suspensions or solutions that are commonly used in the concrete and construction industries In this article, we will delve into the differences between colloidal silica, potassium silicate, and sodium silicate and how each impacts concrete.
What is Colloidal Silica?
Colloidal silica is a stable dispersion or suspension of ultrafine particles of silicon dioxide (SiO2) in a liquid medium. The particle size of colloidal silica is typically in the range of 1-100 nanometers, making it smaller than traditional silica particles found in sand or rocks. Due to its small size, colloidal silica has a large surface area, providing excellent binding properties. Colloidal silica solutions often appear transparent or slightly opaque and can be either acidic or alkaline.
Colloidal silica particles have a negative surface charge, which makes them repel each other and remain suspended in the liquid medium. This property is known as electrostatic stabilization. Furthermore, colloidal silica has a high affinity for water molecules due to its large surface area, leading it to form strong bonds with surrounding water molecules. These properties make colloidal silica an excellent binder and stabilizer in concrete.
What is Potassium Silicate?
Potassium silicate is a compound composed of potassium oxide (K2O) and silicon dioxide (SiO2). It comes in different forms, including liquids, powders, or granules. Potassium silicate solutions are highly alkaline with pH values ranging from 10-12. Due to its alkalinity, it is often used as a corrosion inhibitor and adhesion promoter in coatings and paints.
When potassium silicate is mixed with water, it forms silicic acid (H4SiO4). This acid dissociates into silicate ions (SiO32-) and potassium ions (K+), which are responsible for the alkaline nature of potassium silicate solutions.
What is Sodium Silicate?
Sodium silicate, also known as water glass or soluble glass, is a compound composed of sodium oxide (Na2O) and silicon dioxide (SiO2). It is available in both liquid and solid forms, with the liquid form being more commonly used in various industries. Sodium silicate solutions have a high alkaline pH ranging from 11-13.
Similar to potassium silicate, when sodium silicate comes into contact with water, it forms silicic acid, which dissociates into sodium and silicate ions. These ions are responsible for the high alkalinity of sodium silicate solutions.
How Does Colloidal Silica Differ from Pottasium Silicate and Sodium Silicate when used in Concrete?
Colloidal silica is a dispersion of ultra-fine amorphous Nano silica particles that are normally grown from ripping and stripping apart potassium and sodium silicates and allowing that silica, that SiO2 to polymerize or to grow on top of each other until it becomes a certain size. Then the growth is stopped and the pure silica is flipped with some type of a cursor on it to create a double layer. This prevents it from sticking to each other when it bounces into other particles or adjacent silica particles. The key thing is a higher purity of silica or a higher content of silica than salt.
Nano silica are larger particles of obscure form of Silica in a given cross sectional area. The potassium, sodium, and lithium silicate is silica or silicate attached to a salt, the carrying agent. Therefore, in potassium, sodium, and lithium silicate dispersions, in a given cross sectional area you're going to have more salt as compared to Colloidal Silica where you have more silica than salt.
Additionally, most potassium, sodium, and lithium silicates will react faster than a colloidal silica dispersion. This is commonly seen in densifying agents. Colloidal silica provides deeper penetration and greater migration of that product into the concrete surface then seen with silicate versions. This is because normally those silicates will react at the surface, creating a gel and slowing down the migration of that solution into the body of the concrete. Silica is not going to react as fast because it is 100 particles compared to the solutes in solution.
Conclusion
Although colloidal silica, potassium silicate, and sodium silicate have similar chemical compositions, they have distinct properties and applications. Colloidal silica is a stable dispersion of ultrafine particles with excellent binding properties, while potassium silicate and sodium silicate are alkaline compounds used as corrosion inhibitors, adhesion promoters, and binders. By understanding the differences between these elements, concrete providers can choose the most suitable solution for their specific needs.