Kaolin, calcined kaolin, washed kaolin, metakaolin.

The uses of kaolin include:
As a necessary mineral raw material for dozens of industries, such as paper making, ceramics, rubber, chemical industry, coating, medicine and national defense, kaolin has certain plasticity, which makes the ceramic mud body conducive to turning, grouting and forming.

The role of kaolin in ceramics is to introduce Al2O3, which is conducive to the formation of mullite and improves its chemical stability and sintering strength.

During sintering, kaolin decomposes into mullite, forming the main framework of green body strength, which can prevent the deformation of products, widen the firing temperature, and make the green body have a certain whiteness.

Metakaolin (MK for short) is an anhydrous aluminum silicate (Al2O3 · 2SiO2, AS2 for short) formed by dehydration of kaolin (Al2O3 · 2SiO2 · 2H2O, AS2H2 for short) at an appropriate temperature (600~900 ℃). Kaolin belongs to layered silicate structure, and the layers are bound by van der Waals bond, in which OH ions are firmly bound. When kaolin is heated in the air, its structure will change several times. When it is heated to about 600 ℃, the layered structure of kaolin will be destroyed due to dehydration, forming a transition phase metakaolin with poor crystallinity. Because the molecular arrangement of metakaolin is irregular, it presents a thermodynamic metastable state and has gellability under proper excitation.

Metakaolin is a kind of highly active mineral admixture. It is an amorphous aluminum silicate formed by ultra-fine kaolin calcined at low temperature. It has high pozzolanic activity, mainly used as concrete admixture, and can also be used to make high-performance geological polymers.