From tomography to mechanics: quantifying corrosion-induced splitting stresses in reinforced mortar

Abstract Corrosion of steel reinforcement is a major cause of deterioration in concrete structures, yet the mechanical response at the steel-mortar interface remains insufficiently understood. This study introduces an image-informed mechanics framework that quantifies the stress–strain behaviour of the corrosion layer and its role in cover cracking. X-ray and neutron computed tomography of a reinforced mortar specimen were used to determine corrosion-induced displacements at the steel-mortar interface. These image-derived displacements were applied as boundary conditions in non-linear finite element analyses that closely reproduced the geometry and loading conditions of the tested specimen, enabling evaluation of the stress–strain response of the corrosion layer. Two cases were analysed: one in which all corroded regions contributed to stress build-up, and one where expansion in regions containing interfacial voids was reduced to account for (near) stress-free expansion into these voids. The analyses revealed that radial stresses at the steel-mortar interface are strongly non-uniform, with only a few corroded regions dominating stress build-up. The quantified stress–strain response of the corrosion layer exhibited a non-linear mechanical behaviour, characterised by an apparent non-linear stiffness that increased with increasing strain, consistent with earlier mechanical characterisations. Overall, this image-informed mechanics framework offers new insights into the stress–strain behaviour of the corrosion layer. The results clarify parameters that govern crack propagation and provide quantitative measures to support future modelling and durability assessment of reinforced concrete.