Corrosion behavior of a steel bar embedded in a cement-based conductive composite

•Corrosion mechanism of rebar in cement-based conductive composite is illuminated.•CF conductive network functions as a large anode of electrochemical corrosion.•Percolation threshold is a critical value that determines corrosion level.

Corrosion behavior of a steel bar embedded in a cement-based conductive composite was the object of study described in this paper. First, the conductivity percolation curve of a carbon-fiber- (CF-) reinforced cement-based composite was obtained. The dry-wet cycle method was then adopted to accelerate the corrosion of the steel bar embedded in the cement-based conductive composite. The corrosion behavior was analyzed using the linear polarization resistance (LPR) technique, the corrosion potential and the weight loss method. In addition, the effect of the CF added on the pore structure was discussed. Finally, it was found that the percolation threshold of CF in the composite is a critical value that determines the corrosion level of the steel bar. The addition of CF has no effect on the corrosion level of the steel bar at the early stage when the CF content is lower than the CF percolation threshold, while the corrosion level tends to increase when the CF content is higher than the CF percolation threshold.