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Per §7.5 (Impact Strength), impact strength of concrete relative to its compressive-strength test results typically shows:
A{'text': 'Much greater scatter than compressive tests', 'label': 'A'}
B{'text': 'Much less scatter than compressive tests', 'label': 'B'}
C{'text': 'Essentially identical scatter', 'label': 'C'}
D{'text': 'No measurable scatter at all', 'label': 'D'}
Answer & Solution
Correct answer: A. {'text': 'Much greater scatter than compressive tests', 'label': 'A'}
1. §7.5 reads: 'impact strength results show greater scatter of result than compressive strength results because compressive strength test is done slowly and gradually which allows relief of high stresses from highly stressed weak zones by way of redistribution owing to creep of concrete.'
2. Impact loading is too fast for creep redistribution; local weak zones dominate failure.
_Source: IGNOU ET-522 Block-2 Unit-7 Strength of Concrete, §7.5, p. 54_
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