A coupled diffusion-mechanical model with boundary element method to predict concrete cover cracking due to steel corrosion

Abstract

Concrete cracking caused by steel corrosion is one of the most important durability issues for reinforced concrete structures. A coupled diffusion-mechanical model has been developed in this study to predict the crack propagation in concrete during the steel corrosion process. The spatial and time distribution of corrosion depth around the steel cross section during the corrosion process is first calculated from the chloride diffusion analysis in the corrosion module. In the mechanical module, for each time moment corresponding to a certain degree of corrosion, the non-uniform corrosion distribution obtained from the corrosion module is adopted as geometric input, and governing equations based on boundary element methods are set up to calculate the extent of cracking in the concrete. Based on two indirect boundary element methods, the fictitious stress method and displacement discontinuity method, the mechanical problem of the concrete/rust/steel composite under rust expansion is formulated. Different concrete fracture properties and rust properties are employed as input in the model to examine their effects on the crack width evolution in concrete. A slab with steel reinforcements of different diameters but at the same concrete cover is analyzed as an example to illustrate the applicability of the developed model in predicting crack width in the concrete cover. The delaying effect of rust penetrating into concrete cracks on the crack width evolution is also simulated with the present model. The developed boundary element model coupling the diffusion and mechanical processes shows the potential for realistic prediction of service life of structures suffering from steel corrosion by taking into account of the interaction effects during the corrosion and concrete cracking processes.