Shearography applied to the non destructive evaluation of bonded interfaces between concrete and CFRP overlays

ABSTRACT A shearographic method is proposed that allows (i) to detect bonding defects (delamination or adhesive disbonds) between concrete structures and externally bonded FRP reinforcements, (ii) to assess the width of these defects, and (iii) to evaluate the quality of the adhesive bond in the case of partial delamination, damage or poor properties of the polymer adhesive. The performance of the method is first demonstrated on laboratory specimens containing calibrated defects, i.e., non adherent polytetrafluoroethylene discs placed at the concrete-to-FRP interface. Then, an example of on-site application illustrates the potential of such method for routine inspections of FRP strengthened structures.