Dynamic property determination for early-age concrete

This paper reports the test results of the dynamic modulus of elasticity an d Poissons ratio of concrete at early age by means of nondestructive evalua tion. The dynamic modulus was measured by a new test apparatus that include s a free-free boundary vibration chamber and a dynamic resonance measuremen t system with a fast, Fourier transform (FFT) analyzer The measurement was conducted on concrete cylinder specimens. The dynamic modulus and Poisson's ratio were calculated using the first two natural frequencies of a cylinde r The measured dynamic response showed very good consistency and reproducib ility. This method enables a measurement of progressive changes in the stif fness of the concrete without damaging the specimen and provides reliable v alues of dynamic modulus. It is found that the age of concrete has a signif icant influence on resonance frequencies; herein, the resonance frequencies shift from lower to higher values in a regular pattern with the age of con crete.