Per §7.2, the presence of 5 percent entrapped air voids in concrete ca…

Question

Per §7.2, the presence of 5 percent entrapped air voids in concrete can typically reduce its compressive strength by approximately:

Accepted Answer

C. {'text': 'About 35 percent of the void-free value', 'label': 'C'}

1. §7.2 states: 'The presence of these entrapped air voids in concrete greatly reduces its strength: 5 percent of voids can lower strength by as much as 35 percent and even 2 percent voids can result in a drop of strength of more than 10 percent.'
2. Hence even modest compaction defects severely hurt strength.
_Source: IGNOU ET-522 Block-2 Unit-7 Strength of Concrete, §7.2, p. 42_

Answer

{'text': 'About 1 percent of the void-free value', 'label': 'A'}

Answer

{'text': 'About 5 percent of the void-free value', 'label': 'B'}

Answer

{'text': 'Effectively zero', 'label': 'D'}