The hardness of clinker in cement mill is important for the energy cost of the grinding process by cement mill. It depends both on the clinker's mineral composition and its thermal history. The easiest-ground clinker mineral by cement mill is alite, so high-alite clinkers reduce grinding costs brought by cement mill, although they are more expensive to make in the kiln than cement mill. The toughest mineral is belite, because it is harder, and is somewhat plastic, so that crystals tend to flatten rather than shatter when impacted in the cement mill. The mode of burning of the clinker is also important. Clinker rapidly burned at the minimum temperature for combination, then rapidly cooled, contains small, defective crystals that grind easily in cement mill. These crystals are usually also optimal for reactivity. On the other hand, long burning at excess temperature, and slow cooling, lead to large, well-formed crystals that are hard to grind in cement mill and un-reactive. The effect of such a clinker can be to double milling costs brought by  cement mill. If you have any interesting with our cement mill,please telephone us: 0086-0371-86079588 or leave us a message: info@zkcorp.com