A numerical approach to determine the intrinsic attenuation of concrete

Ultrasound measurements are used for monitoring the structural health of concrete. The elastic waves propagating in concrete structures are attenuated by scattering and intrinsic attenuation. Both quantities have to be determined for a detailed material characterization and for realistic numerical simulations of wave propagation in such structures. We present in this paper a numerical approach to determine the intrinsic attenuation of concrete. For this purpose, a realistic digital three-dimensional concrete specimen is created that accounts for correct volume fractions of aggregates of different sizes embedded into a mortar matrix. Using a viscoelastic finite difference scheme, we perform simulations of the ultrasound wave field in these digital models with different attenuation levels. The numerical observations are compared with results from ultrasonic measurements on a sample of saturated concrete to estimate the intrinsic attenuation. Embedded sensors are used for those long-term laboratory experiments. For this saturated concrete, we obtain Q=130 in a frequency band around 60 kHz.