The Modelling Study On Corrosion Progress Of Steel And Its Consequent Mechanical Effect For Concrete Structures

Steel corrosion is one of the main reasons for the durability failure of concrete structures.The volume of corrosion products is usually several times larger than that of the original reinforced steel and thus this leads to an internal pressure on the surrounding concrete.With producting corrosion products,the cover concrete will be pulled to crack,and the service life of the concrete structures will reduce.The mechanical effect of steel corrosion is mainly controled by the corrosion rate,the corrosion environment,the mechanical properties of corrosion products,the concrete properties.So far,most of the researches are summarise corrosion laws based on experiments and corrosion predictions through theoretical analyses.It is still in lack of the modeling study on corrosion process of steel and its consequent mechanical effect for concrete structures.The present work aims to explore a simulation method of the corrosion process and its effect on the mechanical deformation which can be used to quantitative analyse the corrosion effect of actual structrues.During the corrosion,the corroded steel is a mixture of steel and corrosion products.In the present work,the volume fraction of the corrosion products is defined to represent the corrosion degree of the material.A constitutive relation of the material is proposed.The equivalent elastic modulus and the coefficient of linear expansion as a function of the volume fraction of the corrosion products are obtained from a two-phase cell model.In the corrosion diffusion equation,the corrosion diffusion coefficient is an important parameter to control the corrosion rate.The corrosion processes of a single steel bar are then modelled to obtain the corrosion rate curves.By comparing the simulated curves with the experimental data in the existing research work,the corrosion diffusion coefficients under the different annual mean of temperature,resistance of concrete and amount of chloride at depth of reinforcement are calibrated.Based on the calibrated parameters including the equivalent elastic modulus,the coefficient of linear expansion,and the corrosion diffusion coefficient,two models,the concrete damage plasticity model and the extended finite element method are used to model the concrete.The predicted cracking time of the concrete protective layer is consistent with the experimental results.The effects of thickness of the protective layer and the diameter of the reinforcement on the fracture pattern of the concrete and protective layer cracking time are further quantified.