Q. Chemical composition of cement is: Answer:
Limestone, Clay and Gypsum
Notes: The two important raw materials used for the preparation of cement are :
Limestone : CaCO3 is used in the manufacture of cement just to provide CaO.
Clay : Clay is hydrated aluminium silicate and iron (iii) oxide having chemical formula Al2O3SiO2Fe2O3.2H2O. Thus, clay consists of aluminium oxide (Al2O3), silicon dioxide (SiO2), and iron (iii) oxide (Fe2O3) along with water molecules.
In addition of limestone and clay, gypsum is also used during preparation of cement. It is added into the cement to slow down the setting of cement when water is added into it.