Quantifying penetration depth of damage in concrete structures using nonlinear elastic wave spectroscopy

Abstract

The ubiquity of concrete as a building material necessitates the ability to inspect and evaluate its structural integrity, preferably in a nondestructive manner. Of particular interest is the ability to detect and quantify the degree to which surface damage penetrates concrete. This is especially important in the nuclear energy industry where concrete is used as a barrier protecting the primary confinement vessel, such as in dry storage casks, in which case cracks form a path for corrosion. Nondestructive evaluation techniques based on the material's nonlinear elastic parameters are orders of magnitude more sensitive to the presence of damage than linear elastic methods analogous to sonar. Two methods, both subsets of Nonlinear Elastic Wave Spectroscopy (NEWS), were used: Nonlinear Resonance Ultrasound Spectroscopy (NRUS) for evaluation of a sample's bulk nonlinear characteristics, and Time Reversal Elastic Nonlinearity Diagnostics (TREND) for evaluation of a sample's local nonlinear characteristics. These nonlinear characteristics are strong indicators of the presence of damage. Eight concrete samples were cut into two pieces, of the two piece one was thermally damaged for 3 h at 500°C. Evaluations of these pieces using NRUS showed a seven times nonlinear parameter increase for the damaged pieces over the undamaged pieces. Using a minimally participating adhesive, samples were glued back together and evaluated using TREND. Results from TREND aligned closely with the expected modeled response. © The Society for Experimental Mechanics, Inc. 2013.