Which one among the following is the correct order of amount of lime (CaO), silica (Si02), alumina (AI203) and ferric oxide (Fe2O3) in Portland cement?

Ordinary Portland cement (OPC) is primarily composed of four major oxides: lime (CaO), silica (SiO2), alumina (Al2O3), and ferric oxide (Fe2O3). According to chemical composition data, lime is the most abundant constituent, typically ranging from 60% to 67%. Silica follows as the second most significant component, comprising approximately 17% to 25% of the mixture. Alumina is present in smaller quantities, generally between 3.0% and 8.0%. Ferric oxide, which provides the characteristic grey color to cement, is found in the lowest proportion among these four, typically ranging from 0.5% to 6.0%. This hierarchical distribution is essential for the formation of complex compounds like tricalcium silicate and dicalcium silicate during the kiln process. Therefore, the correct descending order of abundance is CaO > SiO2 > Al2O3 > Fe2O3.