Corrosion of exposed rebars, associated mechanical degradation and correlation with accelerated corrosion tests

In a large number of steel reinforced concrete buildings in Greece, spalling of the cement has left the steel reinforcement (rebars) exposed to the atmosphere. This has led to corrosion of the exposed rebars, especially in coastal areas, with questions regarding their remaining load-carrying capacity. This work addresses the problem of corrosion and strength degradation of such exposed rebars. A large number of samples (sections of exposed rebars) were collected from buildings up to 96 years old, and weight loss measurements, tensile testing and fractographic analysis were carried out. Accelerated corrosion testing (salt spray) was performed on new similar grade rebars in order to establish a correlation with the naturally corroded exposed rebars.It was found that exposed rebars suffer from uniform corrosion followed by degradation of mechanical properties. In certain cases the properties were below the minimum threshold required by the international standards. A rough estimate of the correlation factor between natural corrosion of exposed rebars and salt spray corrosion has been derived. This correlation factor could be used, under certain limitations, to estimate the condition, in terms of mechanical property degradation and structural integrity, of coastal buildings with exposed rebars in Greece.

► The problem of natural corrosion of exposed rebars in coastal areas is addressed.
► Tensile testing and evaluation of samples up to 96 years old was performed.
► Accelerated salt spray corrosion testing was performed on new, similar grade rebars.
► A correlation factor which may be applied under conditions has been estimated.
► Findings were supported by fractographic and metallographic analysis.