What Raw Materials Are Used for Cement Production
The main raw materials for the production of Portland cement clinker are calcareous raw materials and clay raw materials.
Calcareous raw material
Raw materials containing calcium carbonate as the main component are all calcareous raw materials. It can be divided into natural calcareous raw materials and artificial calcareous raw materials. Commonly used in cement production is natural ore containing calcium carbonate (CaCO3).
Types and characteristics of calcareous raw materials
- Limestone: It is a chemical and biochemical sedimentary rock composed of calcium carbonate. Main mineral: it is composed of calcite (CaCO3) particles, and often contains dolomite (CaCO3•MgCO3), quartz (crystalline SiO2), vermiculite (also known as vitreous quartz, flint, the main component is SiO2, which belongs to crystalline SiO2). Iron and other impurities. CaO content: pure limestone contains CaO56%, the loss on ignition is 44%, and the CaO content decreases with the increase of impurity content. Water content: generally not more than 1.0%, the specific value varies with the climate. The more impurities contain clay, the higher the moisture.
- Marl: is a uniformly mixed sedimentary rock formed by the simultaneous deposition of calcium carbonate and clay. It is an intermediate type of rock that transitions from limestone to clay. It is an excellent cement raw material. Classification: High Calcium Marl: CaO ≥ 45% ; Low calcium marl: CaO <45%. In some places, the composition of marl is close to the raw material for making cement. It can be directly fired into cement, which is called natural cement rock. Main mineral is calcite.
- White peony: also named chalk, it is a mixture of shells and of marine organisms. It is rich in biological remains, mainly composed of cryptocrystalline or amorphous fine-grained calcium carbonate. The main ingredient: calcium carbonate, the content of 80% -90%, and even higher than 90%. Performance: Easy to grind and calcinate, it is the high quality calcareous raw material of Lianya Cement Plant.
- Shells and corals: mainly shells, clams and coral stones. Main ingredients: about 90% calcium carbonate. The surface is covered with mud and salt (such as MgCl2, NaCl, KCl) and other substances that are harmful to cement production, so rinse with water when using. At present, some small coastal cement plants use this raw material.