The compressive strength figure in the BIS designation '53 Grade OPC' refers to the minimum 28-day strength of:
A{'text': '33 MPa', 'label': 'A'}
B{'text': '43 MPa', 'label': 'B'}
C{'text': '63 MPa', 'label': 'C'}
D{'text': '53 MPa', 'label': 'D'}
Answer & Solution
Correct answer: D. {'text': '53 MPa', 'label': 'D'}
1. §1.7(A) lists three BIS grades — 33 Grade (IS-269), 43 Grade (IS-8112), 53 Grade (IS-12269) — and adds: 'The figures 33, 43, 53 refer to minimum 28 days strength of these cements in MPa.'
2. Table 1.4 confirms 53 Grade OPC at 672±4 hours (28 days) reaches 53 MPa.
_Source: IGNOU ET-522 Block-1 Unit-1 Cement, §1.7(A) and Table 1.4, pp. 10 and 13_
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