Influences of corrosion degree and corrosion morphology on the ductility of steel reinforcement

Tensile tests were first conducted on the steel reinforcement corroded by long-term (26–28 years) exposures to a chloride-rich natural environment. Through the tests, besides the corrosion degree, which was the most often used parameter to assess the corrosion, the corrosion morphology (i.e. represented by the radius of gyration of the residual cross-section) was found to be a very important factor influencing the ductility of the steel reinforcement and three typical corrosion morphologies were identified. Afterwards, tensile tests on a series of steel reinforcement artificially made with the above three types of corrosion morphologies, which were simulated through mechanically induced cross-sectional losses, were conducted with the aim of quantifying the relationship between the ductility of the corroded reinforcement and the corrosion degree and morphology. It was found that, for all the corrosion morphologies, that the ultimate strain of the corroded steel reinforcement was reduced in an exponential manner with the corrosion degree up to a critical level (30% by mass loss), beyond which it then stayed stable. However, different corrosion morphologies led to significantly different degradation rates with the corrosion degree. A model was proposed to describe the above relationships and validated through comparisons with test results on both the artificially simulated and the naturally corroded steel reinforcement.