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Per §8.2, the gel pores of hydrated cement paste have a porosity of about 28 percent but contribute LITTLE to overall permeability because:
A{'text': 'The gel pores are completely filled by calcium hydroxide as hydration proceeds in the paste body', 'label': 'A'}
B{'text': 'Their pore size is so small that water cannot pass; gel permeability is only about 1/100th of paste', 'label': 'B'}
C{'text': 'They form open continuous capillary channels for water to leave at every drying interface', 'label': 'C'}
D{'text': 'Air entrainment during mixing forces all gel pores shut for the lifetime of the hardened paste', 'label': 'D'}
Answer & Solution
Correct answer: B. {'text': 'Their pore size is so small that water cannot pass; gel permeability is only about 1/100th of paste', 'label': 'B'}
1. §8.2 reads: 'The gel has porosity of 28 percent, but its pores are so small that appreciable amount of water cannot pass through them. In fact the permeability is only 1/100th of that of the paste. Therefore, you could say that gel pores do not contribute to the permeability of the concrete.'
2. Capillary cavities (whose size depends on w/c) are the real permeability path.
_Source: IGNOU ET-522 Block-2 Unit-8 Durability of Concrete, §8.2, p. 66_
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