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Geology QUESTION #10657
Question 1
Which of the following can serve as raw material for the manufacture of Portland cement?
  • Limestone
  • Iron ore (hematite)
  • Marine shells (calcium carbonate)
  • All of these✔️
Correct Answer Explanation
Portland cement is manufactured by heating a mixture of calcium carbonate ($\text{CaCO}_3$) and silica/alumina/iron sources. Suitable raw materials include:
  • Limestone (most common CaCO₃ source)
  • Marine shells (also CaCO₃)
  • Hematite/iron ore (iron source for the iron phase in cement clinker)
The kiln product (clinker) contains alite (C₃S), belite (C₂S), aluminate (C₃A), and ferrite (C₄AF) phases. All three options are valid raw materials.