Date of this Version
Published (2023) Journal of Nondestructive Evaluation, 42 (4), art. no. 93, .DOI: 10.1007/s10921-023-01003-2
Nonlinear acoustic methods demonstrate high sensitivity for concrete damage evaluation. Among these methods, nonlinear resonance acoustic methods have been widely used in laboratory tests on small scale test samples. In this study, a nonlinear impact-echo (IE) method was proposed for concrete damage evaluation, in which the IE frequency shift was measured at different impact force levels. The nonlinear IE test is similar to the nonlinear impact resonance acoustic spectroscopy (NIRAS) test in the experimental setup and analysis method. How- ever, the nonlinear IE test excites a local thickness resonance mode of a member instead of the global resonance vibration. Therefore, the analyzed mode is not affected by boundary conditions and can be applied to large concrete structural members. To identify the fundamental IE frequency, multiple impacts at different locations were used. The nonlinear IE method was then validated on seven concrete beam specimens with different levels of alkali-silica reaction (ASR) damage. The nonlinear IE test results demonstrate high sensitivity to concrete damage and allow for quantitative assessment of the damage state of concrete without a baseline measurement.