Effect of Interfacial Transition Zone on diffuse ultrasound in thermally damaged concrete

Abstract

The correlation between Interfacial Transition Zone (ITZ) and the diffusion of ultrasound for the Non Destructive Evaluation of thermally damaged concrete is investigated in this study. As most damages first emerge from the ITZ, it is necessary to understand the ultrasonic wave/ITZ interaction. This paper focuses on the use of the diffusivity parameter to characterize thermal damage within the microstructure. A numerical model accounting for real ITZ characteristics and validated through a previous study is used to assess the effects of ITZ on diffusivity values. Diffusivity measurements are performed on real concrete specimens with different thermal damage states. Comparison of experimental and numerical data exhibits a strong correlation between the ultrasonic diffusivity, the thermal damage level and the ITZ contact level. A direct correlation between diffusivity and ITZ characteristics is suggested. This result is a major step toward the development of quantitative ultrasonic methods for the NDE of concrete.