In the present study, the effects of direct current (DC) stray current on concrete structures were studied with the focus on the effect of concrete rather than corrosion of steel bars. Concrete samples were prepared with different water/cement (w/c) ratio and silica fume (SF) content were submerged in distilled water for 30 days while subjected to a voltage of 50 V direct current (VDC). The effects DC stray current on the properties of concrete were determined by electrochemical impedance spectroscopy (EIS) and rapid chloride penetration (RCP) tests. The obtained results showed that DC stray current will increase permeability of the concrete. The critical role of w/c ratio and SF additive on the degradation effects created by DC stray current was investigated. Moreover, a mechanism based on the migration of calcium and hydroxyl ions out of the pore solution and the dissolution of Ca(OH)2 precipitates from the hydrated phase was proposed for the explanation of DC potential on the degradation of concrete.