Durability diagnosis of a concrete structure in tidal zone by combining NDT methods: laboratory tests and case study

To successfully implement non-destructive techniques (NDTs) for surveying concrete structures in marine environments, non-destructive measurement results must be correlated with concrete durability indicators such as porosity and water and chloride contents. For this purpose, tests introducing two elec- tromagnetic methods (GPR and the capacitive technique), as well as the impact-echo method, were run on six different concrete mixes containing various porosities, with five water content values and three chloride concentrations. A reinforced concrete beam, extracted from the wharf of the Nantes-Saint-Nazaire Port, exposed to ocean tides was also tested under actual conditions. The NDT laboratory results exhibit linear correlations with concrete indicators, which in turn allows building a three-dimensional empirical model. This 3D cross-correlation model, coupled with onsite NDT results, is then used to perform a dura- bility diagnosis of the actual structure. Moreover, these results serve to illustrate the advantages of the 2D data fusion models developed during this project