engleski

Numerical Analysis of Reinforced Concrete Structures Exposed to Chloride Induced Corrosion

Reinforced concrete structures, which are exposed to aggressive environmental conditions, such as structures close to the sea or highway bridges and garages exposed to de-icing salts, often exhibit damage due to corrosion. Damage is usually manifested in the form of cracking and spalling of the concrete cover caused by the expansion of the corrosion product around the reinforcement. The repair of corroded concrete structures is related with relatively high direct and indirect costs. Therefore, it is of great importance to have a model, which is able to realistically predict influence of corrosion on the safety and durability of RC structures. To estimate reduction of the cross-section area of reinforcement and to predict the increase of the volume of the corrosion product it is necessary to know the corrosion rate i.e., corrosion current density in the corrosion unit. The calculation of corrosion current density requires modeling of the following physical, electrochemical and mechanical processes: (i) transport of capillary water, oxygen and chloride through the concrete cover ; (ii) immobilization of chloride in the concrete ; (iii) transport of ions through electrolyte in concrete pores (iv) cathodic and anodic polarization, (v) transport of corrosion products in concrete and cracks and (vi) damage of concrete due to mechanical and non-mechanical actions. In the present contribution the 3D chemo-hygro-thermo-mechanical model for concrete is presented. In the model the interaction between the non-mechanical properties (distribution of temperature, moisture, oxygen and chloride) with the mechanical properties of concrete (damage) is accounted for. The mechanical part of the model is based on the microplane model. The strong and weak formulations and implementation into the 3D finite element code are discussed. The application of the model is illustrated on numerical examples in which the transient 3D finite element analysis of RC slab is carried out. First example includes only initiation phase of corrosion and shows the influence of damage of concrete on depassivation time of reinforcement. Comparison between numerical and experimentally observed corrosion rates shows that the model is able to realistically predict corrosion of reinforcement.

Reinforced Concrete; Corrosion; Chloride; Transport processes; Corrosion Rate; Microplane Model; Finite Elements

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