Active additives for the modification of cement systems have been widely used in production for more than a decade. They are used to give Portland cement-based compounds greater strength, chemical resistance and durability. One of the most common pozzolanics today is metakaolin.
In fact, metakaolin is a chemical phase formed during the processing of kaolin under high temperature conditions. This modifier reacts well with lime released during the hydration of Portland cement and forms insoluble binders. It has high moisture requirements, strong thickening ability, improves the consistency of concretes and other mortars, and increases the effectiveness of surfactants. Metakaolin also has a very good effect on the adsorption of solutions.
Another characteristic property of metakaolin is the instability of several its properties, including color, activity, reaction rate. For this reason, manufacturers using this additive must be prepared for some variation in the color of the finished product. Another property, which in certain cases may seem like a disadvantage, is the ability of metakaolin to increase the stickiness of cement and concrete mortars. This practically does not allow using it in its pure form when grouting, smoothing and spackling – as a rule, additional additives are used for these methods.
Metakaolin is mainly used in working with cement materials, concretes and dry mixes. Experience shows that replacing only eight percent of concrete or cement with metakaolin can increase the early strength of the mortar by 15%. In addition, metakaolin in the composition of concrete, cement and dry building mixtures increases the density of the final product. Another advantage of this substance is its ability to reduce the consumption of plasticizers and redispersible powders, which are quite expensive materials. It is used in the production of highly mobile, fine-grained self- levelling and self-compacting types of concrete.