Why is gypsum added to cement clinker during grinding?
A{'text': 'To raise the early heat of hydration of the mix', 'label': 'A'}
B{'text': "To improve the cement's resistance to freezing damage", 'label': 'B'}
C{'text': 'To replace the lime component in the mix design', 'label': 'C'}
D{'text': 'To prevent flash set caused by C3A reacting with water', 'label': 'D'}
Answer & Solution
Correct answer: D. {'text': 'To prevent flash set caused by C3A reacting with water', 'label': 'D'}
1. §1.5(d): 'The reaction of pure C3A with water is very fast and may lead to flash set. Gypsum is added at the time of grinding to prevent this flash set.'
2. Gypsum (2-3 percent, §1.2) thus regulates the setting time of cement.
_Source: IGNOU ET-522 Block-1 Unit-1 Cement, §1.5(d) and §1.2(e), pp. 6 and 8_
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