The wireless efficiency of the strongly coupled magnetic resonance (SCMR) method is studied here for non-homogenous interfaces. Specifically, SCMR's wireless power transfer from a source in air to a sensor embedded in concrete is analyzed. The concrete material properties are modeled for various humidity levels using the extended Debye model. The performance of SCMR is examined for both plain and reinforced concrete. Finally, rectification of the RF power is performed and the DC power delivered to the embedded sensor's battery is calculated.