Effects of sand aggregate on ultrasonic attenuation in cement-based materials

Ultrasonic wave attenuation measurements have been successfully used to characterize the microstructure and mechanical properties of inhomogeneous materials; these ultrasonic techniques have the potential to provide for the in-situ characterization of microstructure changes in cement-based materials due to damage. Recent research has applied acoustic scattering models to quantitatively predict ultrasonic attenuation for evaluating the air void content in hardened cement paste. The objective of the current research is to investigate the influence of sand aggregate on the ultrasonic attenuation as a first step towards a full simulation of more realistic microstructures in real concrete. Hardened cement paste samples containing sand aggregate of varying volume fractions are considered. The research employs an independent scattering model and a self-consistent effective medium theory to predict the scattering-induced attenuation of longitudinal ultrasonic waves by the sand inclusions distributed in the cement paste matrix. The predicted attenuation coefficients are compared with measured ones. It is observed that at low volume fractions, both models provide a good estimate of the total attenuation in the specimens. These results indicate that it is possible to use a physics-based model to quantify the effect of sand aggregate on ultrasonic attenuation.