In reference document 1，there is a little description concerning a dry concrete electric resistivity. The author etc. clarified the relation between a concrete percentage of moisture content and electric resistivity in the state of moist in reference document 2 to 4. In this research，the relation between a concrete material age and the electric resistance was investigated by the type experiment with a water tank. And，grounds that were able to use the structure as an earth electrode were specified. Additionally，the relation between a concrete electric resistivity and the ground resistance was clarified by a numeric calculation.
