ULTRASONIC PULSES BEHAVIOR IN CONCRETE DURING COMPRESSIVE LOADING

The paper investigates the variation of ultrasonic pulse velocity, attenuation and frequency in concrete udder uniaxial compressive loading Experimental results indicate that the pulse velocity in concrete is independent of the stress level to a large extent, up to about 70% of the compressive strength. This means, in practical terms, that stresses prevailing in the concrete of a structure do not have to be taken into account when pulse velocity data are used for the evaluation of the quality of concrete. Compared with velocity, the amplitude of ultrasonic waveform has higher sensitivity to the extent of cracking. In order to improve the reliability of measurement, thepaper combines velocity, amplitude and frequency to propose a damage coefficient D as anindicator of crack growth. The results proposed in this paper are useful for improving reliability of non-destructive test of concrete, and determining the extent of damage due to load, creep, shrinkage,and other environmental effects.