The study of the influence of concrete crack width on corrosion of steel reinforcement due to exposure to aggressive environments is very important for durability design. Premature failure of structures may eventually occur during their service life. Since cracks in the concrete cover are inevitable due to the stress structures are subjected to, penetration of aggressive substances will occur more rapidly in cracked areas than in areas without cracking. This study addresses the corrosion effects on the reinforcement in cracked areas. Reinforced beams 2 m long and cracked at half-length with widths up to 1 mm were prepared 20 years ago, exposed to carbonation and chlorides and kept outdoors sheltered from rain until present. After 20 years, the carbonation depth in the faces of the cracks, and the reinforcement at the crack region have been examined. The results indicated that flexural cracks in high quality carbonated concrete present only a small additional risk of corrosion which, however, is significant in the presence of chlorides.
The number of reinforced concrete structures subject to anoxic conditions such as offshore platforms and geological storage facilities is growing steadily. This study explored the behaviour of embedded steel reinforcement corrosion under anoxic conditions in the presence of different chloride concentrations. Corrosion rate values were obtained by three electrochemical techniques: Linear polarization resistance, electrochemical impedance spectroscopy, and chronopotenciometry. The corrosion rate ceiling observed was 0.98 µA/cm2, irrespective of the chloride content in the concrete. By means of an Evans diagram, it was possible to estimate the value of the cathodic Tafel constant (bc) to be 180 mV dec−1, and the current limit yielded an ilim value of 0.98 µA/cm2. On the other hand, the corrosion potential would lie most likely in the −900 mVAg/AgCl to −1000 mVAg/AgCl range, whilst the bounds for the most probable corrosion rate were 0.61 µA/cm2 to 0.22 µA/cm2. The experiments conducted revealed clear evidence of corrosion-induced pitting that will be assessed in subsequent research.
It is commonly mentioned that corrosion of steel in presstressed concrete can induce brittle failure. It is also understood that in order to estimate the presstressed structures service life is necessary to study the pitting factor that compares the maximum corrosion pit depth with the section loss by homogeneous corrosion. Results are presented on corrosion tests to measure the corrosion depth in tendons in contact with water. In present paper, a statistical analysis has been carried out in order to obtain the pitting factor for different cross sections submerged in water. The results indicate that the pitting factor value varies between 1.20 and 1.85 depending on the confidence interval considered, which can significantly reduce the service life of the presstressed tendons as long as the exposure conditions are those set out in this study.
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