Studies recently indicated that certain tools from nonlinear acoustics seem to be promising for the characterization of cracks or micro-cracks developed in concrete structures. Only a few of them are currently applied in the field because their implementation causes various problems. This paper proposes a new method based on nonlinear acoustics to characterize the concrete damage associated with the alkali-silica reaction (ASR), a common deterioration process affecting numerous concrete structures. This method consists in quantifying the influence of an external mechanical disturbance on the propagation of an ultrasonic compression wave in the material. When a damaged material is subjected to continuous ultrasonic pulses while a punctual mechanical perturbation is generated, the pulse velocity is suddenly reduced due to the opening of the micro-cracks. Then it slowly and gradually returns to its initial value while the micro-cracks are closing. This variation is associated to the nonlinear attenuation observed to process the nonlinear parameter. This new method was applied on concrete specimens affected by ASR. The results confirmed the relevant of this nonlinear technique in order to better evaluate the effects of ASR on concrete structures.

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