Characterizing internal macropores using cross-specimen acoustic tomography: Verification of two dimensional results

The engineering properties of a geologic material are greatly affected by the presence of macropores. Previous research has demonstrated that the size, location, and proximity of macropores influences both the strength and stiffness of specimens. Knowledge of the distribution of macropores in a specimen prior to testing would be useful for a number of reasons. We are currently developing a non-destructive method called cross-specimen acoustic tomography (CSAT) to determine the number, location, and size of the macropores in a laboratory specimen. The CSAT method uses a set of piezoelectric sensors that generate and receive high frequency acoustic waves. We measure the travel times of the acoustic waves through a specimen and then use a commercially available tomography software package to invert the data. The inverted velocity model is in turn used to locate the voids within the specimen. The verification of two dimensional (cross-sectional) results from plaster specimens containing large macropores of Styrofoam show the technique is promising and worthy of further development.