Numerical Simulation Of Concrete Degradation Due To Chloride Induced Steel Corrosion

The presence of chemicals in sea water or in marine areas is a major concern for engineers tasked with the design and the construction of planned engineering structures as these structures are constantly subjected to attack by these chemicals.Concrete structures built in marine environment are susceptible to attack by chemicals such as chloride which diffuses into concrete structures and attack the reinforcements embedded in reinforced structures.This research focuses on the numerical simulation of the processes involved in the structural degradation and to allow for proper understanding if the degradation process of concrete.Corrosion begins when the chloride concentration reaches critical value and with increased corrosion,damage is induced in the concrete,which endangers the serviceability and affects the response of these structures to different forms of loading.ABAQUS Finite Element Software was used to analyse processes involved in concrete structure degradation from chloride diffusion to steel corrosion and the concrete cover cracking.The mass diffusion algorithm in ABAQUS presented a spatial and time dependent solution to the chloride diffusion mechanism in a sound concrete element,with respect to a constant surface chloride concentration.The steel corrosion process in concrete was determined analytically and its effect was described and used on the finite element model.The mass loss from steel corrosion was obtained using Faraday's law,while the reduction of the effective size of the rebar,the corrosion rate and volumetric change of the corrosion product was all determined.Pressure due to the tensile stress generated by expansive nature of the corrosion product at the concrete-steel interface was modeled by applying uniform radial displacements.Concrete was modelled by the concrete smeared cracking approach in ABAQUS,while the Extended Finite Element Method(XFEM)solution was employed to appropriately model concrete cover cracking.Obtained results show that the chloride concentration decreases with depth of penetration,but increases with exposure time at the concrete-steel interface.A loss of the effective size of the rebar was obtained,followed by an increase in the mass loss due to corrosion.Damage in concrete is seen in form of cracks which appear and propagate as pressure caused by the expansive nature of the corrosion product increases.Main cracks and other radial cracks are seen round the concrete-steel interface which is the point of application of the radial displacement.Established crack pattern are obtained with an increase in the crack width with corrosion time.This research work provides an understanding of the corrosion mechanism in concrete due to the action of chloride ions on steel reinforcement,while it also gives the cracking pattern with a full use of the Extended Finite Element Method.