A nondestructive acoustic approach for the detection and quantification of damage in mortars affected by delayed ettringite formation (DEF) is used to study the degradation mechanism at micro- and macro-scales. The presentation considers a linear acoustic technique, dynamic elastic modulus, which measures the macro-scale damage, and a nonlinear acoustic technique, Nonlinear Impact ResonanceAcoustic Spectroscopy (NIRAS), which assesses the damage at the micro-scale. Both methods successfully differentiate the degree of DEF-damage in mortars experiencing various expansion levels. Variable Pressure Scanning Electron Microscopy (VP-SEM) images and Energy Dispersive X-Ray Spectroscopy (EDS) microanalysis are used to confirm the microstructural distress caused by DEF. Results indicate that mortars are damaged both during the early-age high-temperature curing and subsequent limewater exposure. However, the microcracking occurred during the early age high-temperature curing cycle is only detectable using nonlinear acoustic measurements. Furthermore, results from expansion, relative change in dynamic elastic modulus, standard deviation of average nonlinearity parameter, and corrected cumulative average nonlinearity parameter are in agreement with each other
