Consequences of steel corrosion on the ductility properties of reinforcement bar

In all concrete constructions besides the common strength problems, in presence or not of seismic activity, serious problems from environmental attack may be presented which significantly decrease their durability and service lifetime. The most common case of construction deterioration is the corrosion of steel reinforcement. The initiation mechanisms leading to steel depassivation, such as concrete carbonation and chloride penetration, have been thoroughly studied and modeled in the past. However, for the corrosion propagation period still there are no acceptable models to simulate the corrosion rate and further to estimate precisely the time when the corrosion progress signals the end of the structure service life. In the present work, the main corrosion initiation mechanisms are shortly presented. Further, the propagation period and the main consequences on mechanical properties of steel and concrete are analyzed. The experimental results show that with increasing duration of exposure to a corrosive environment, the steel mass loss increases appreciably. This leads to a significant increase of the applied stress. In addition, a significant reduction of the tensile ductility of the material was observed. For laboratory salt spray exposure periods, some of the tensile properties of steel bars drop to values lying below the limits, which are set in the existing standards for using steels in reinforced concrete members. The experimental results from the accelerated corrosion tests on bare steel bars are in a good qualitative agreement with results from steel bars embedded in aged concrete.