Influence of electrochemical chloride extraction on the bond between steel and concrete

Laboratory tests were undertaken to assess the effect of electrochemical chloride extraction (ECE) on the bond strength of plain reinforcing steel in concrete. Specimens were cured/stored for 3 months prior to ECE and were then treated at a current density of between 0.02 and 0.75A/m(2) of reinforcement area for periods of up to 32 weeks. Chloride-free specimens showed a small gradual increase in bond strength after ECE. Prior to ECE, specimens containing chloride (1.5% by weight of cement) had higher bond strength than chloride-free specimens, due to corrosion. This enhanced bond strength was largely eliminated by 2 weeks of ECE, due to dissolution of corrosion products, although these specimens also then showed a slight increase in bond strength after further treatment. Tests carried out 10 min, 24 h and 28 days after ECE suggest that bond strength reduces during ECE. Variations in bond strength are considered with regard to the processes occurring during ECE, and the practical implications of these findings are discussed.