Bond failure of steel rebar corrosion in concrete with different degrees of steel

Abstract

The present study concerns the service life of concrete structure under the risk of corrosion of steel. Since the serviceability and safety of concrete are mainly governed by the structural behaviour at steel corrosion, the structural limit was taken as the parameter to the service life rather than the onset of corrosion. A reduction of the bond strength, compared to uncorroded steel rebar, was regarded as the threshold structural limit and the bond strength of steel was measured at the variation of corrosion degree with respect to the diameter of steel rebar. The corrosion was generated by the charge extraction on the surface of steel rebar to evenly form the rust on steel, instead of a permeation of corrosive ions/molecules to the depth of the steel such as chlorides and carbonation of cover concrete. As a result, it was found that the corrosion rate was equated to about 2–8 mA/m2 at the corrosion initiation detected by the mass loss of steel. At the structural limit in terms of the bond reduction, the degree of corrosion and corrosion rate were affected by the diameter of steel rebar. An increase in the diameter of steel rebar resulted in an increase in the charge extraction, but the corrosion rate was adversely reduced by the increased surface area of steel. The corrosion rate at the structural limit accounted for 227.4–555.3 mA/m2, depending on the steel size, of which information can be used to monitor the structural limit of concrete at steel corrosion. © 2025 Institution of Structural Engineers