Relationship between porosity, permeability and ultrasonic parameters in sound and damaged mortar: Fid-Bau Portal

Relationship between porosity, permeability and ultrasonic parameters in sound and damaged mortar

Goueygou, M. / Lafhaj, Z. / Kaczmarek, M.

The relationship between porosity, permeability and acoustic parameters of mortar samples measured by ultrasonic NDT is investigated. In order to enhance the sensitivity of the ultrasonic wave to microstructure, a high frequency range (0.3 to 1.3 MHz) is chosen. In sound samples, despite a significant dispersion of experimental results, the expected trends were observed. Phase and pulse velocity decrease with porosity and permeability. The attenuation behaviour depends on material saturation. It was found to increase with porosity in dry samples, with just the opposite trend in water saturated samples. An interesting result is the change from positive to negative dispersion as frequency increases. Porosity of samples was further increased by chemical damage. Due to excessive attenuation, only the pulse velocity of longitudinal and shear waves could be measured. No clear correlation could be obtained between porosity and acoustic velocity in damaged samples. This is probably due to experimental problems that could be solved by carefully washing the samples prior to ultrasonic testing. This study also highlights the difficulty of obtaining accurate estimates of ultrasonic parameters, because of the high variability of the material under study. Solving this problem would require a fair amount of experimental data and an appropriate equipment to acquire weak signals. The present study shows how ultrasonic parameters are expected to evolve as physical parameters related to damage vary. This observation is significant from the viewpoint of the undertaken project focused on quantitative interpretation of data acquired on site using ultrasonic NDT techniques.