Bond between ribbed bars and concrete. Part 2: The effect of corrosion

Abstract

The corrosion products that form 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. Thereby, the bond between the reinforcement and the concrete is influenced. A model of the corrosion was developed by the author in earlier work. This was used together with a modified model of the bond mechanism, presented in a companion paper, in three-dimensional finite element analyses where both the reinforcement and the concrete were modelled with solid elements. Several corrosion cracking tests, beams and pull-out tests with corroded reinforcement, both with and without transverse reinforcement, carried out by various researchers, were analysed by using the corrosion model. The results were compared, and reasonably good agreement was found. Furthermore, 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; in addition, the crack pattern differed. From these analyses, it was concluded that axisymmetric analyses appear to be a sufficient level of modelling when studying cracking due to uniform corrosion. If localised corrosion is to be studied, three-dimensional models need to be used. The model was also used to study the effect of uniform corrosion on the anchorage length when no transverse reinforcement is present. Under these circumstances, the criterion ‘the anchorage of the reinforcement becomes critical when cracking of the cover occurs’ was shown to be on the safe side to use.