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Per §8.3.1, sulphate-resisting Portland cement provides high resistance because it is manufactured with a content of C3A (tricalcium aluminate) of not more than:
A{'text': '5.5 percent', 'label': 'A'}
B{'text': '1.0 percent', 'label': 'B'}
C{'text': '10.0 percent', 'label': 'C'}
D{'text': '30.0 percent', 'label': 'D'}
Answer & Solution
Correct answer: A. {'text': '5.5 percent', 'label': 'A'}
1. §8.3.1(iii)(a): 'High resistance to sulphate attack has been found for portland cements containing not more than 5.5 per cent C3A.'
2. C3A reacts with sulphates to form calcium sulpho-aluminate, whose ~227 percent volume increase is the disruption mechanism.
_Source: IGNOU ET-522 Block-2 Unit-8 Durability of Concrete, §8.3.1(iii)(a), p. 68_
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