**9.4 Non-destructive evaluation for risk and asset Management of Bridges**

This project aimed at evaluating reinforced concrete bridge elements using two non-destructive evaluation (NDE) techniques, namely ultrasonic pitch and catch (UPC) and ground-penetrating radar (GPR). State-of-the-art literature reviews on multiple cutting-edge NDE techniques were carried out to identify potential knowledge gaps. **Figure 7** shows the basic principles of the UPC technique.

A validation test for a reinforced concrete slab specimen with embedded steel rebars and wire meshes was conducted to identify the advantages and limitations associated with the UPC and GPR techniques. **Figure 8** shows 3D visualization of the test specimen using NDT/NDE GPR and UPC (MIRA). **Figure 9** shows twodimensional reconstructed image at an artificial delamination location. The highresolution electromagnetic GPR technique accurately located almost all embedded reinforcements in the 3D slab volume tested.

The UPC technique detected rebars with large diameters while small diameter rebars and wire meshes could not be accurately detected. However, unlike the image obtained from the GPR data, 3D visualization reconstructed from the UPC's data showed very strong reflections of the slab bottom. The UPC technique usually requires multiple-point scanning for the targeted survey areas, resulting in a timeconsuming data collection and processing. The research team recommended the combined use of the GPR and UPC techniques to comprehensively assess RC bridge elements, where the GPR is used to quickly evaluate questionable/defected regions while the UPC technique is used for an in-depth inspection/evaluation.
