In the manufacture of Portland cement, clinker is the solid material produced by the cement kiln stage that has sintered into lumps or nodules, typically of diameter 3-25 mm.

Clinker, if stored in dry conditions, can be kept for several months without appreciable loss of quality. Because of this, and because it can easily be handled by ordinary mineral handling equipment, clinker is traded internationally in large quantities. Cement manufacturers purchasing clinker grind it as an addition to their own clinker at their cement plants. Manufacturers also ship clinker to grinding plants in areas where cement-making raw materials are not available.

You can find our clinker specification here.