alleryStart learning →Per the source, when grinding clinker to produce Portland cement, the percentage of gypsum added by weight is:
A2 to 3 percent
B1 to 2 percent
C5 to 7 percent
D10 to 12 percent
Answer & Solution
Correct answer: A. 2 to 3 percent
1. §1.2 (Wet process, e): 'Finally this clinker is ground in a ball mill with 2 to 3 percent of gypsum to produce portland cement.'
2. Gypsum is added to prevent the flash set otherwise caused by C3A reacting violently with water (§1.5 d).
_Source: IGNOU ET-522 Block-1 Unit-1 Cement, §1.2(e) and §1.5(d), pp. 6 and 8_
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