Measuring the layer thicknesses of concrete coatings by mobile NMR – A study on the influence of steel reinforcements

A large number of infrastructural concrete buildings are protected against aggressive environments by coating systems. The functionality of these coating systems is mainly affected by the composition and thickness of the individual polymeric layers. For the first time ever, a mobile nuclear magnetic resonance (NMR) sensor allows a non-destructive determination of these important parameters on the building site. However, before this technique can be used on steel-reinforced concrete elements, the potential effect of the reinforcement on the measurement, i.e. the NMR signal, needs to be studied. The results show a shift of the NMR profile as well as an increase of the signals amplitude in the case of the reinforced samples, while calculating the thickness of concrete coating lead to identical results.

► I present a tool for non-destructive testing of polymeric coatings on concrete.
► I examine the influence of steel reinforcement on the NMR signal.
► Affected by the reinforcement the NMR profile shift, the amplitude increase, the thickness does not change.
► A method is presented in order to measure and correct the profile displacement due to reinforcement.