Non destructive evaluation of concrete contamination by chloride Comparison of methods

This paper aims to analyse the sensitivity of some NDT methods (radar, resistivity and capacitive technique) to chloride contamination. In laboratory, four different concretes with different water to cement ratio and two kinds of aggregates were conditioned with different saturation degrees of two solutions (30 g/l or 120 g/l of NaCl). NDT measurements show that the attenuation of radar waves is sensitive to the presence of chlorides but depending on the saturation degree of the solution while velocity is not affected. Resistivity is also very sensitive. The real permittivity measured at low frequency with capacitive technique is modified by the presence of chlorides. All the techniques were carried out on a real site. From the analysis of laboratory results, an attempt of evaluation of both moisture content and level of chloride contamination is proposed and compared to values obtained from cores extracted on a very near area.