Abstract: A method of calcining kaolin, comprising the steps of:a) producing a clay slurry comprised of water and kaolin clay of a specific particle size;b) mixing a water insoluble potassium containing glass forming compound into the clay slurry in an amount wherein the potassium content of the slurry is equal to about 1% by weight of the kaolin clay in the slurry;c) removing sufficient water from the slurry to form a material having an extrudable consistency;d) extruding the material into elongated shapes;e) heating the shapes by continuously moving them through a furnace having a zone, wherein the material is exposed to temperatures of at least 2700.degree. C. for at least 30 minutes.

Abstract: A method of forming powdered metakaolin for use as an additive in cement based materials comprising the steps of calcining kaolin so as to reduce the hydroxyl content thereof to produce a meta-stable material have an identifiable amorphousness, and pulverizing the meta-stable material into a powder having a particle size of 50 microns or less.