1. Raw Materials:

* Limestone (CaCO3): This is the primary source of calcium oxide (CaO), which is a key component of cement.

* Clay (Al2O3, SiO2, Fe2O3): These oxides provide the necessary aluminum, silicon, and iron oxides for the clinker formation.

* Other materials: Gypsum (CaSO4.2H2O) is added later for controlled setting.

2. Chemical Reactions in the Kiln:

* Calcination: Limestone decomposes into calcium oxide and carbon dioxide (CaCO3 → CaO + CO2).

* Sintering: The mixture of calcium oxide, silica, alumina, and iron oxide undergoes a series of complex chemical reactions at high temperatures (around 1450°C) to form clinker. This is the key stage where the chemical properties of cement are determined.

3. Grinding and Mixing:

* Clinker Grinding: Clinker is ground into a fine powder.

* Gypsum Addition: Gypsum is added to control the setting time of the cement.

4. Hydration and Setting:

* Chemical Reaction with Water: When water is added to cement, a complex chemical reaction occurs called hydration. This reaction releases heat and forms a hardened paste that binds the aggregates together.

So, the "chemical part" of cement is not just a single component, but the entire process of its creation, from the raw materials to the final hardened product. The chemical reactions and the resulting properties are what make cement a vital construction material.