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Per §8.7, which of the following is named as a PRE-HARDENING (early-age) crack cause in concrete?
A{'text': 'Drying shrinkage from long-term moisture loss in cured concrete', 'label': 'A'}
B{'text': 'Corrosion of reinforcement decades after construction', 'label': 'B'}
C{'text': 'Structural failure under live load on the hardened structure', 'label': 'C'}
D{'text': 'Plastic shrinkage from chemical reactions soon after placing', 'label': 'D'}
Answer & Solution
Correct answer: D. {'text': 'Plastic shrinkage from chemical reactions soon after placing', 'label': 'D'}
1. Table 8.7 lists pre-hardening crack causes as: subgrade settlement, formwork movement, settlement around reinforcement / formwork obstructions, plastic shrinkage (chemical reactions soon after placing under moist conditions) and drying shrinkage (rapid drying while setting).
2. Drying shrinkage post-set, structural failure and reinforcement corrosion appear in Table 8.8 (post-hardening).
_Source: IGNOU ET-522 Block-2 Unit-8 Durability of Concrete, Tables 8.7 and 8.8, §8.7, p. 76_
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