Portland cement (J. Aspdin) contains maximum % of CaO. Cement clinker contains A) limestone & clay as raw materials

B) SiO2 to Al2O3 ratio 2.5 to 4.0 or

C) gypsum, fly ash and black ash (Na2CO3 + CaS)

D)

The correct option is D

Explanation:

The major raw material used in making cement clinker is limestone. This limestone is usually mixed and heated with clay and can sometimes be mixed, in addition to the clay, with fly ash, black ash, bauxite, iron ore and gypsum. However, the product cement clinker contains different calcium silicates and/or aluminates such as Ca₃SiO₅, Ca₃Al₂O₆, Ca₂(Al,Fe)₂O₅ and Ca₂SiO₄. Thus, the correct option is D.