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Per Table 8.1, the coefficient of permeability of cement paste at a fixed w/c of 0.7 drops by approximately how many orders of magnitude between FRESH state and full hydration ('Ultimate')?
A{'text': 'About 1 order of magnitude (factor of 10)', 'label': 'A'}
B{'text': 'About 2 orders of magnitude (factor of 100)', 'label': 'B'}
C{'text': 'About 4 orders of magnitude (factor of ten-thousand)', 'label': 'C'}
D{'text': 'About 7 orders of magnitude (factor of ten-million)', 'label': 'D'}
Answer & Solution
Correct answer: D. {'text': 'About 7 orders of magnitude (factor of ten-million)', 'label': 'D'}
1. Table 8.1 lists coefficient of permeability: 2 × 10⁻⁶ m/s (fresh) and about 6 × 10⁻¹³ m/s (ultimate, calculated).
2. That is a drop from 10⁻⁶ to 10⁻¹³, i.e. about 7 orders of magnitude — illustrating why curing is critical.
_Source: IGNOU ET-522 Block-2 Unit-8 Durability of Concrete, Table 8.1, §8.2, p. 66_
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