A comparison study of constant current and square wave current in the bidirectional electromigration rehabilitation on chloride-contaminated concrete

Abstract

The objective of this study is to reduce the hydrogen embrittlement risk of rebar caused by the continuous constant current (CC) in the bidirectional electromigration rehabilitation (BIEM). Three types of square wave current (SWC) were applied in the BIEM treatment on a Cl--contaminated concrete, in the saturated calcium hydroxide containing 1 mol/L triethylenetetramine (TETA). The sample experienced the BIEM with a constant current density of 3 A/m2 was chosen as the control sample with the same electricity consumption. After 4 cycles of treatment, the concentration profiles of Cl- and TETA were measured in the protective layer. The corrosion current densities of the rebar were analyzed by various electrochemical tests. The stress-strain curve of the rehabilitated rebar was tested, and its hydrogen embrittlement risk was estimated. The results suggested that the SWC more effectively removed Cl- and migrated TETA than the CC did, with the same electricity consumption and treatment duration. The rebar experienced the former BIEM exhibited a higher fracture energy ratio and a lower corrosion rate than the one experienced the latter treatment. In general, the SWC was more effective and lower hydrogen embrittlement risk than CC in the BIEM rehabilitation treatment.