In the hydration of Portland cement, Calcium Hydroxide is considered undesirable because it:
A{'text': 'Gets leached out and causes porosity in concrete', 'label': 'A'}
B{'text': 'Increases early compressive strength', 'label': 'B'}
C{'text': 'Reacts with gypsum to form ettringite', 'label': 'C'}
D{'text': 'Lowers the heat of hydration significantly', 'label': 'D'}
Answer & Solution
Correct answer: A. {'text': 'Gets leached out and causes porosity in concrete', 'label': 'A'}
1. §1.5(a) reads: 'Calcium Silicate Hydrate and Calcium Hydroxide are produced. Calcium Hydroxide is considered undesirable as it gets leached out causing porosity in Concrete.'
2. The strength contribution belongs to the C-S-H gel (Tobermorite gel) of §1.6, not to Ca(OH)2.
_Source: IGNOU ET-522 Block-1 Unit-1 Cement, §1.5(a), p. 8_
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