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Per §4.5, the most commonly known retarding admixture used in cement industry is:
A{'text': 'Sucrose (cane sugar) added during mixing', 'label': 'A'}
B{'text': 'Sodium chloride dissolved in the mixing water', 'label': 'B'}
C{'text': 'Sodium silicate liquid added at the batch plant', 'label': 'C'}
D{'text': 'Calcium sulphate (gypsum) inter-ground with clinker', 'label': 'D'}
Answer & Solution
Correct answer: D. {'text': 'Calcium sulphate (gypsum) inter-ground with clinker', 'label': 'D'}
1. §4.5: 'The most commonly known retarder is calcium sulphate. It is interground to retard the setting of cement.'
2. Sugar is one of the most effective retarders (0.2 percent can delay final set by 72+ hours) but is not the standard inter-grinding agent.
_Source: IGNOU ET-522 Block-1 Unit-4 Admixtures, §4.5, p. 48_
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