10-10-2014, 02:18 PM
The dynamic properties such as pamping constant and resonant frequency of
concrete and mortar are important parameters in design of dynamically loaded
concrete structures. In services, concrete could have suffered some internal
micro-cracking due to stresses acting on them. Hence it is essential to know the
influence of such cracking on the logarithmic decrement, etc. of concrete.
In the present investigation a total of 34 specimens cast out of two mortar mixes
and two concrete mixes are tested using “Sonic Resonance Test”. One mortar mix
and one concrete mix each having six specimens were subjected to “Sonic
resonance test” which is at minimum of five repetition for each specimen. In this
type of test the order of difference for logarithmic decrement was 6% in case of
mortar, and 15% in case of concrete which is due to heterogeneity of concrete and
mortar mixes. From the other mixes tested for sonic resonance test before and
after the application of different percentages of ultimate prior-stress. Logarithmic
decrement decreases with increases of prior-stress up to 40% of ultimate stress,
and increases with increase of prior-stress after 40% of ultimate stress. There was
considerable scatter in the result.
The dynamic modulus, in general, found to be higher than static modulus and
also found to decrease with increase of prior-stress.