3. Metakaolins: definitions and parameters governing their reactivities

Metakaolins (Al ₂ O ₃ , 2SiO ₂ ) are obtained by calcining kaolin clay at temperatures between 500 and 800°C. Heat treatment results in the destruction of the crystalline structure and dehydroxylation of the initial kaolin (loss of structural water). The processes most commonly used for the commercial production of metakaolin are rotary, flash and plate furnaces.