Cement has 4 main components, namely Calcium oxide(CaO) which makes up about 60-67% of cement, Silicon DIoxide(SiO2) which covers about 17-25% of cement, Aluminium Oxide(Al2O3) which is 3-8% helps in setting and hardening process and Iron oxide (Fe2O3) of 0.5-6% helps in giving colour to the cement.