Characterization of the microstructure of cement-based materials using ultrasonic attenuation

Ultrasonic techniques have the potential to provide quantitative information about the microstructure of cement-based materials. A critical parameter in describing ultrasonic wave propagation is attenuation. Attenuation refers to the energy loss associated with both scattering and absorption. It has been observed that the two major sources of ultrasonic attenuation are absorption due to the viscoelastic effects, of the medium and the scattering from inhomogencities. This research considers the propagation of ultrasonic waves through an isotropic, viscoelastic medium containing randomly distributed spherical voids the medium is a representation of a cement paste matrix containing a moderate percentage (on the order of 10%) of approximately 1mm-diameter spherical inclusions (i.e. entrained air to resist freeze/thaw damage). An analytical model is used to predict attenuation under the assumption of no scattering interaction between the air voids. Experimental measurements are made on samples prepared with varying amounts of air entrainer, and these results are compared to analytical predictions. There is a good agreement between measured and predicted values, and these results are used to quantify the effect of microstructure on the attenuation of ultrasonic waves in cement-based materials.