Relation between ultrasound propagation velocity and path length in solid concrete

Conclusions

In ultrasonic tests of concrete quality in thick-walled structures (more than 0.5 m thick) and in massive blocks in hydraulic structures, it is necessary to take into account change in the amplitude-frequency spectra of ultrasound pulses with the path length in the concrete, which is a regular phenomenon associated with the normal absorbing properties of the concrete. This must be distinguished from the changes indicating quality deterioration or structural defects in the concrete. The quantitative decrease in the velocity of propagation of ultrasound along a ray in the direction of each sounding depends on the physicomechanical properties of the concrete, its composition, its age, and the natural frequency of the ultrasound-pulse emitter-transducer; for measurement bases between 1 and 6 m, it lies in the range 1–12%. Correction coefficients δ for assessing the effect of this factor can be found with sufficient accuracy for practical purposes from the measured acoustic characteristics of the concrete, in conjunction with the theoretical relation (13) or the graphs in Fig. 6.