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Per §8.2, ways listed in the source to IMPROVE the impermeability of concrete include all EXCEPT:
A{'text': 'Use of pozzollonic materials (prevents Ca(OH)2 leaching)', 'label': 'A'}
B{'text': 'Air entrainment up to about 6 percent', 'label': 'B'}
C{'text': 'Increasing the water-cement ratio above 0.7', 'label': 'C'}
D{'text': 'High-pressure steam curing', 'label': 'D'}
Answer & Solution
Correct answer: C. {'text': 'Increasing the water-cement ratio above 0.7', 'label': 'C'}
1. §8.2 lists three improvements: (i) use of pozzolonic materials, (ii) air-entrainment up to 6 percent, (iii) high-pressure steam curing (which gives a coarser gel and lower drying shrinkage).
2. Increasing the water-cement ratio is the OPPOSITE — Table 8.1 makes clear that lower w/c is required to reduce permeability; w/c > 0.7 in §3.2 of Unit-3 was already shown to leave unblockable capillaries.
_Source: IGNOU ET-522 Block-2 Unit-8 Durability of Concrete, §8.2, pp. 66-67_
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