Electrical impedance spectroscopy (EIS) is a powerful technique to study material properties, e.g., it is highly sensitive to the moisture content of inhomogeneous cementitious materials. This study contributes to the in-situ measurement of the moisture content (MC) in concrete during the decommissioning of nuclear power plants. Thus, a comprehensive investigation of dielectric material properties of concrete has been performed experimentally and over a 10{{\ Hz}} to 10\text{MHz} range of frequencies through alternating current (AC) impedance spectroscopy.