If the raw meal is not homogeneous enough, units of varying sizes will exist which do not have the required chemical composition. It can be easily deduced from the phase diagram for the system CaO - Al₂O₃ - Fe₂O₃ - SiO₂ the phase compositions which can coexist assuming different volumes have different chemical composition. In Fig. 1 the different phase assemblages in the system CaO - Al₂O₃ - SiO₂ can be seen.

Fig.1: Possible mineral assemblages in the system CaO - Al2O3 - SiO2

With inhomogeneous raw feeds we should expect a clinker microstructure of varying mineralogy. In reality, this model also exists in the clinker. Fig. 2 shows a clinker with a very inhomogeneous distribution of alite, belite and free lime, reflecting the non-homogeneity of raw material.

Fig.2: Inhomogeneous distribution of clinker minerals. 64 X

In comparison to the inhomogeneous microstructure produced from an inhomogeneous raw mix, Fig. 3 shows the clinker fabric when the raw mix is correctly homogenized. All the minerals are statistically distributed.

Fig.3: Homogeneous distribution of minerals. 250 X

In additional to the effects caused by oversize particles, the concentrated areas due to inhomogeneous distribution contain normally more than one clinker component, and usually extend over a larger area.

According to experience, however, a certain clustering , particularly of belite, is always observed in plant clinker. The even distribution in Fig. 3 is rather an exception.