The synergy of ultrasonic experiments, numerical analyses of wave propagation and scattering theories in cementitious materials

Abstract

The final properties of cementitious materials (strength and durability) strongly depend on the mix proportions and the fresh state of the latter. It is therefore imperative to investigate the early stages, assess the quality of the mixes as well as monitor their time evolution. In this direction, ultrasonic measurements, since many decades, have been proposed as the most efficient tool for quality control and condition characterization due to their ability to inspect, detect, locate and continuously monitor the material’s performance throughout the entire lifetime. However, wave propagation can be quite complicated, especially if the material heterogeneity and wave-microstructure interactions are taken into account. For this reason, in the current study, the ultrasonic experiments are complemented by numerical analyses of wave propagation offering the advantage of easier, faster, repeatable and parametric implementation. The strong dispersion and attenuation trends observed in both the experiments and the numerical tests make, herein, the additional implementation of scattering theories necessary as the third pillar. The results show good match between the experimental and the numerical methods as well as between the numerical simulations and scattering theories, thus providing a more holistic insight of wave propagation in microstructured cementitious materials. In the framework of this study, cement pastes and mortars (containing sand or glass beads as aggregates) are investigated, while the results are demonstrated in terms of pulse velocity and attenuation as a function of frequency revealing interesting information on the influence of the aggregate content on the quality of the mixes.