According to Table 1.1 (Oxide Composition Limits) of OPC, the permissible CaO content lies in the range:
A{'text': '40 to 50 percent', 'label': 'A'}
B{'text': '60 to 67 percent', 'label': 'B'}
C{'text': '70 to 80 percent', 'label': 'C'}
D{'text': '85 to 95 percent', 'label': 'D'}
Answer & Solution
Correct answer: B. {'text': '60 to 67 percent', 'label': 'B'}
1. Table 1.1 in §1.3 lists CaO content as 60 to 67 percent.
2. The remaining options do not match the limit table.
3. SiO2 by contrast is 17 to 25 percent, Al2O3 is 3 to 8 percent, and Fe2O3 is 0.5 to 6.0 percent.
_Source: IGNOU ET-522 Block-1 Unit-1 Cement, Table 1.1, §1.3, p. 6_
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