Characterization of cement-based multiphase materials using ultrasonic wave attenuation

Ultrasonic wave attenuation measurements have been used to successfully characterize the microstructure and material properties of inhomogeneous materials; these ultrasonic techniques have the potential to provide for the in situ characterization of heterogeneous, cement-based materials. Recent research has applied existing acoustic scattering models to predict ultrasonic attenuation in relatively simple cement-based materials with good results. The goal of the current research is to extend this past work and to investigate the influence of elastic inclusions in order to simulate a more realistic microstructure: a cement paste matrix material that contains both sand inclusions and air voids. The sand inclusions simulate fine aggregates as they are present in real civil engineering structures, while the air voids provide an additional microstructure that is present in concrete components. This research considers an independent scattering model as well as a self-consistent effective medium theory approach in order to model the scattering attenuation due to the sand inclusions in the cement paste matrix. The research develops a reliable measurement technique essential to assess the wave attenuation of the particulate materials. Subsequently, the ultrasonic wave attenuation is measured in cement paste specimens of various types. The measured attenuation is then compared to the model predictions and the results are discussed. Finally, theoretical approaches to model the described three-phase materials are presented and discussed.M.S.Committee Chair: Jacobs, Laurence J.; Committee Member: Kim, Jin-Yeon; Committee Member: Qu, Jianmi