Application of nonlinear elastic resonance spectroscopy for damage detection in concrete

Nonlinear resonance ultrasound spectroscopy experiments were conducted on naturally aged concrete cores, one chemically and mechanically damaged by alkali-silica reactivity (ASR), and a similar sample showing little ASR damage. Both exhibited nonlinear behavior, similar to many other damaged materials. It was found that the damaged sample responds more nonlinearly, manifested by a larger resonant peak shift, i.e., modulus shift, as a function of strain amplitude. Further, as in many other materials, slow dynamics were present. The nonlinear response observed in these two concrete samples demonstrates that nonlinearity is an extremely sensitive indicator of damage. The results and story---now over two decades old---of how these experiments came about are revisited in this talk with an eye on future research and funding possibilities and to discuss lessons learned in the marketing of this research.