There are four stages in the manufacture of Portland cement:
(1) crushing and grinding the raw materials,
(2) blending the materials in the correct proportions,
(3) burning the prepared mix in a kiln,
(4) grinding the burned product, )clinker(
together with some 5 percent of gypsum (to control the time of set of the cement). The three processes of manufacture are known as the wet, dry, and semidry processes and are so termed when the raw materials are ground wet and fed to the kiln as a slurry, ground dry and fed as a dry powder, or ground dry and then moistened to form nodules that are fed to the kiln.