Pump and probe wave mixing for imaging nonlinear features embedded into a massive concrete block

International audience ; Nonlinear ultrasonic parameters are known to be highly sensitive to the presence of damage in materials, and numerous methods have already been reported. This study proposes a way to image a nonlinear defect embedded into a nonlinear medium. The nonlinear defect is mimicked by a Berea sandstone sphere (high nonlinearity). It is placed into a large concrete block (average nonlinearity) during casting. The proposed pump and probe propagating wave interaction method allows imaging the presence of the highly nonlinear region. The image contrast is magnified by a factor 8 in the defective zone. The results are validated using a model and the individual mechanical properties of both concrete and Berea Sandstone. These findings open perspectives for application to civil engineering concrete structures such as the assessment of durability distresses involving internal swelling.