A dummy segment from a bored tunnel with cast-in MREs was used to investigate if the moisture content of the concrete lining could be determined. The results were compared with two other in-situ resistivity measurements and correlated to the moisture content measured on cores drilled from the dummy and stored at various relative humidities. In addition, a capillary suction set-up was placed over the MREs and the capillary suction was measured, together with the changes in electrical resistivity. The results indicate that wetting front upon suction can be clearly seen. As a consequence, possibly leakages of (salty) water in the tunnel can be monitored well. On the other hand, the change in resistivity over longer periods of time, proved more difficult to interpret. Nevertheless, it is expected that the wetting front in the tunnel lining can be seen, so that an estimate of the maximum possible carbonation depth can be established.© 2009 Taylor & Francis Group.