Increasingly more non-destructive testing methods are being developed in a civil engineering context, but many of them cannot be applied when only one surface of the structure can be accessed. In order to measure moisture level in such concrete structures as dams or tunnels, a coplanar line was designed, capable to measure the permittivity evolution as well as the loss factor. Measurements on salinity of water and setting of mortar were performed, showing a dependence on physical magnitudes of interest with the electrical parameters measured.