Quantification of non-uniform distribution and growth of corrosion products at steel-concrete interface.

• The growth of corrosion products around the steel-concrete interface is investigated. • Statistically significant number of samples are measured by using BSE imaging. • Corrosion induced by impressed current is non-uniformly distributed around the steel-concrete interface. • Most corrosion products reside at the bottom side of steel bar with respect to casting direction. • The amount of corrosion products increases with the increase of w/c ratio. • Smaller concrete cover results in smaller corrosion layer initially but larger in longer term. • The proposed equivalent uniform thickness of corrosion layer is in line Faraday's law. The expansive nature of corrosion products at the steel-concrete interface directly leads to the cracking and spalling of steel reinforced concrete, and its premature failure. In this paper, fundamental causes that affect the distribution and growth of corrosion products at the steel-concrete interface are quantitatively examined. The thickness of the layer of corrosion products and its growth with time are measured accurately using the technique of backscattered electron imaging and with a statistically significant number of samples, which are then verified with Faraday's law. A model for the distribution and growth of the non-uniform corrosion layer is developed. It is found in the paper that the corrosion products are non-uniform around the steel-concrete interface, with the maximum at the bottom side of steel bar with respect to casting direction. It is also found that the amount of corrosion products increases with the increase of water to cement ratio of concrete. The significance of this research is that it has quantitatively examined the effect of microstructure of the steel-concrete interface, a fundamental factor, on the distribution and growth of corrosion products. Findings presented in the paper can contribute to the accurate prediction of corrosion-induced cracking of steel reinforced concrete and hence prevent its premature failure. [ABSTRACT FROM AUTHOR]