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Per §4.7, air entrained in concrete typically consists of minute spherical bubbles in the size range of:
A{'text': 'About 5 to 80 microns in size', 'label': 'A'}
B{'text': 'Less than 1 micron in size', 'label': 'B'}
C{'text': 'About 200 to 500 microns in size', 'label': 'C'}
D{'text': 'About 1 to 5 mm in size', 'label': 'D'}
Answer & Solution
Correct answer: A. {'text': 'About 5 to 80 microns in size', 'label': 'A'}
1. §4.7: 'Entrained air is minute spherical bubbles of size ranging from 5 microns to 80 microns distributed evenly in the entire mass of the concrete.'
2. These bubbles act like ball bearings, improve workability, and interrupt capillaries — they are NOT large entrapped voids.
_Source: IGNOU ET-522 Block-1 Unit-4 Admixtures, §4.7, p. 49_
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