The main raw materials for cement clinker manufacture are calcareous and argillaceous materials, typically limestone (about 75%) and marl (about 25%), respectively.
Quarried limestone is a rock consisting predominantly of calcium carbonate (CaCO3), while marl contains calcium carbonate and clay minerals (Mx/n [xAl2O3·SiO2]·zH2O). The raw materials also contain silica (SiO2), alumina-bearing materials, iron oxides and magnesium compounds.
To ensure the final product has the required chemical composition, the raw-material proportions may be adjusted by adding small amounts of corrective materials, such as quartz and iron ore.
Limestone and marl are extracted from quarries in blocks with typical 1–2 m in size (figures below) and transported to the crusher, where their blocks size is reduced.
