Effect of the tide on permittivity values obtained on a reinforced concrete bridge in marine environment

Summary Main damage occurring on reinforced concrete (RC) structures can be attributed to the corrosion of the rebar. When dealing with structures in marine environment, chloride ion penetration and water content must be considered, as the different exposure zones (tidal, splash and atmospheric) will have a significant influence. GPR survey were performed on several piles and processed to evaluate the evolution of the surface permitivity vs. elevation in the tidal and splash areas. For that, a in-house software by HK Polytechnic university was used to estimate the local radar wave velocity for each location of rebar. The objective herein is to estimate if any vertical gradient of water/chloride content in the surface content. GPR results show a notable decrease of water content between the tidal and the atmospheric area, and no significant information on any gradient of chloride content vs. elevation.