Modelling the splitting effects of corrosion in reinforced concrete

The corrosive products that forms when reinforcement in concrete corrodes occupy a larger volume than the steel it was formed of, thus leading to splitting stresses acting on the concrete. The mechanical behaviour of rust was studied by a combination of analyses and test results found in the literature. This led to the assumption that rust behaves like a granular material, i.e. its stiffness increases with the stress level. This mechanical behaviour, and the volume increase of the corrosive products compared with the virgin steel, were modelled in a corrosion layer. Several corrosion cracking tests carried out by various researchers were analysed using the corrosion model in finite element analyses. The concrete was modelled with non-linear fracture mechanics, using a smeared rotating crack model. The corrosion level that caused cracking of the cover in the tests and in the analyses was compared, showing a reasonable good agreement. The model was used to study the effect of uniform or localised corrosion. It was shown that for localised corrosion, less average corrosion penetration was needed to crack the cover than for uniform corrosion. Furthermore, the crack pattern differed. From these analyses, it was concluded that axisymmetric analyses appear to be a sufficient level of modelling when studying uniform corrosion. If localised corrosion is to be studied, three-dimensional models need to be used.