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Per §7.6.1, the dynamic modulus of elasticity of concrete determined by ultrasonic-pulse / longitudinal-vibration tests is typically:
A{'text': 'Substantially LESS than the static (secant) modulus', 'label': 'A'}
B{'text': 'Zero, because the elastic limit is never reached', 'label': 'B'}
C{'text': 'Identical to the static (secant) modulus', 'label': 'C'}
D{'text': 'Substantially HIGHER than the static (secant) modulus', 'label': 'D'}
Answer & Solution
Correct answer: D. {'text': 'Substantially HIGHER than the static (secant) modulus', 'label': 'D'}
1. §7.6.1 reads: 'dynamic modulus is rather much higher than secant (static) modulus of elasticity. This difference is due to creep occurring in later case and also due to the fact that heterogeneity of concrete affects the two modulus in different ways.'
2. The dynamic modulus relates to ultrasonic pulse velocity v via E = ρ v² (1+μ)(1-2μ)/(1-μ).
_Source: IGNOU ET-522 Block-2 Unit-7 Strength of Concrete, §7.6.1 and Eq. 7.14, p. 57_
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