DETERMINATION OF WATER CONTENT PROFILES IN CONCRETE USING THE INVERSION OF PERMITTIVITY MEASUREMENTS BY CAPACITIVE PROBE

Abstract

The assessment of durability indicators is an importanttask for civil engineers. The indicators are used to monitorthe health condition of reinforced concrete structures andto plan the maintenance. When it comes to the penetrationof aggressive chemicals in cover concrete, the water con-tent plays an important role. Therefore, in this study, wepresent a methodology to obtain the water content profilesversus the depth in the concrete structure. To this aim,capacitive probes are used, known for their sensitivity tothe dielectric permittivity of the tested material. capacitive probes are composed of metallic plates forminga capacitor with the tested material. Three different typesof plates are applied for different investigation depthsdepending on the spacing between the plates and their size.Since each measurement integrates a certain volume of thematerial, an inversion procedure is needed in order toobtain the profiles of permittivity. First, the inversionmethodology that we have developed is presented, and thenit is applied to an experimental campaign of water imbibi-tion on two different concrete formulations. The resultsshow high sensitivity and accuracy of the capacitive tech-nique to detect water content in concrete.