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Per §4.7, air entrained in concrete typically consists of minute spherical bubbles in the size range of:

AAbout 5 to 80 microns in size
BLess than 1 micron in size
CAbout 200 to 500 microns in size
DAbout 1 to 5 mm in size
Answer & Solution
Correct answer: A. About 5 to 80 microns in size
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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