The grinding and blending operations are then completed with the materials in slurry form. After blending, the mixture of raw materials is fed into the upper end of a tilted rotating, cylindrical kiln. The mixture passes through the kiln at a rate controlled by the slope and rotational speed of the kiln. Burning fuel consisting of powdered coal or natural gas is forced into the lower end of the kiln. Clinker is discharged red-hot from the lower end of the kiln and transferred to various types of coolers to lower the clinker to handling temperatures.
Cooled clinker is combined with gypsum and ground into a fine gray powder.
This fine gray powder is portland cement. Types of Portland Cement Different types of portland cement are manufactured to meet various physical and chemical requirements. Specification C-150 provides for eight types of portland cement. Type I portland cement is a normal, general-purpose cement suitable for all uses. It is used in general construction projects such as buildings, bridges, floors, pavements, and other precast concrete products.