Influence of stress on passive behaviour of steel bars in concrete pore solution

The influence of stress on passive behaviour of steel bars in concrete pore solution was studied with electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. The passive ability of steel decreased as the applied load increased and higher load had much greater influence on passivation than repeated loading of small magnitude. A micro-crack model was presented to explain the damage of passive layer by loads. Lower load caused micro-cracks in the passive film which might be completely recovered after unloading. Under higher load more micro-cracks were produced in the passive film and some may penetrate the film, leading to irreversible damages.

Research highlights
► The influence of load on passivity of steel in concrete pore solution is studied.
► The passivity of steel in pore solution decreased as the load amplitude increased.
► A micro-crack model is presented to explain passive behaviour of steel under loads.