Frequency-dependent stress wave attenuation in cement-based materials

Ultrasonic techniques are a widely used, reliable form of nondestructive testing of materials. The nature of concrete as a heterogeneous mixture makes it somewhat ill-suited as a conductor of stress waves, and therefore makes the interpretation of ultrasonic data difficult. In order to quantify the attenuation of ultrasonic waves in concrete, a point source/point receiver (PS/PR) ultrasonic test system was set up, and the individual components were evaluated. PS/PR can be used to quantify (among other things) the ultrasonic attenuation in the materials. The technique was applied to a series of four portland-cement-based test specimens. These specimens ranged from a fine cement paste to concrete sample with a maximum aggregate size of 10 mm. The frequency-dependent attenuation was evaluated for each specimen. The results of this investigation showed that the wave-propagation characteristics of the materials can be quantified with this technique, and that certain characteristics of the attenuation curves can be linked to the degree of inhomogeneity in the material.