Numerical Simulation of Chloride Front Movement into Stressed Reinforced Concrete (original) (raw)
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Simulation Study on Diffusion of Chlorides in Concretes with Load-Induced Heterogeneous Stress
2024
Ingress of chlorides (Cl −) in concretes is influenced by external applied loads, and it is difficult to conduct a quantitative conclusion via experiments due to the geometry of concrete components and their different mechanical and chemical properties. To assist indepth understanding on Cl − ingress in loaded concretes, a numerical model considering different mechanical and transport properties of three concrete components (paste, aggregate, and interfacial transition zone), heterogeneously distributed stress generated by axial loads and the consequent change in Cl − diffusion property at micro level, is established with COMSOL. Its accuracy and functionality have been verified with lab-based results from compressed and tensile samples at a macro level. The obtained results suggested that the model can effectively reveal stress distribution, generation, and propagation of cracks and Cl − diffusion in loaded concretes. Based on this model, it can be deduced that without considering the heterogeneous mechanical and transport properties of concrete components, the extent of Cl − ingress in concretes could be quite close when the induced stress is lower than 40% of the ultimate damaging stress; in comparison, it would be underestimated once the compressive or tensile loads exceed 60% of the ultimate damaging stress. Under 60% compressive loads, the Cl − ingress depth is decreased by 66%, while that is increased by roughly 40% for a 60% tensile loads.
Simulation of Chloride Migration in Compression-Induced Damage in Concrete
Journal of Materials in Civil Engineering, 2012
The ingress of chloride ions in a harsh chloride environment leads to the corrosion of reinforcing steel bars and reduction in the service life of concrete structures. Prediction of the service life of chloride-exposed concrete structures is strongly dependent on chloride diffusion coefficient, which in turn is influenced by several factors including materials and environmental parameters, binding of chloride ions to the solid phase of concrete, and the stresses caused by external load acting on the structure. The diffusion of chloride in concrete is increased significantly by damage associated with load-induced stress, which, if not taken into account, can lead to erroneous prediction of the service life. This paper investigates the impact of compressive stress-induced damage on chloride transport in concrete. An experimental investigation involving non-steady-state migration test as per NT BUILD 492 was carried out on unloaded concrete specimens damaged under axial compressive load. Numerical simulation of the rapid chloride-migration test using multiphysics finite element software is presented in which a phenomenological damage model and a chloride-binding isotherm coupled with Nernst-Planck equation is used to evaluate chloride migration in the damaged concrete specimens.
Enhancement in Chloride Diffusivity due to Flexural Damage in Reinforced Concrete Beams
Journal of Materials in Civil Engineering, 2014
A multiphysics formulation for chloride diffusion in an RC beam with stress-induced damage quantifying the enhancement in chloride diffusivity due to damage is presented. An experimental investigation involving measurement of chloride profile was conducted on RC beams damaged under applied flexural stress. Numerical simulation of the RC beam is carried out using a two-dimensional finite-element approach incorporating the damage due to the applied stress, chloride binding, and the chloride diffusion in the model. Concrete is assumed to be a perfectly elastoplastic (Drucker-Prager) material and the steel as an elastoplastic (von Mises) material with hardening. Drucker-Prager parameters, cohesion c, and friction angle φ are obtained by calibrating numerical load-deflection (P-Δ) curve to an experimentally determined (P-Δ) plot for beams loaded in flexure. Defining a scalar damage index as the degradation in elastic modulus expressed in terms of total strains, the chloride transport problem is addressed, using an effective diffusion coefficient, D effd , expressed as a function of the damage index and chloride binding and obtained by calibrating to data for chloride profiles as determined in flexurally damaged beams. Using the expressions for the effective diffusion coefficient, D effd , the chloride profiles are shown to match the experimentally determined chloride profiles in beams damaged at various stress levels.
Numerical Simulation of Reinforced Concrete Deterioration—Part 1: Chloride Diffusion
ACI Materials Journal, 1999
The deterioration of the U.S. highway infrastructure is a major concern today. In particular, the deterioration of concrete bridge decks due to chloride-induced corrosion of the reinforcing steel is progressing rapidly. If left unchecked, reinforcing steel corrosion can lead to service, financial, and safety problems for concrete bridges. While much experimental and field work has been performed to study bridge deck deterioration and determine solutions, little work has been done to apply a rigorous and comprehensive mechanics-based investigation to the deterioration process. The deterioration process contains three basic components: chloride diffusion, electrochemical corrosion, and concrete fracture. This paper describes the first process, and it will be shown that commercial codes can indeed be used to provide a rigorous framework for chloride diffusion in terms of various parameters.
Numerical Simulation of Concrete Degradation due to Chloride-Induced Reinforcement Corrosion
2018
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 and break down the reinforcement protective layer. This paper presents the use of Abaqus Finite Element Analysis software in Analyzing the processes involved in concrete structure degradation from chloride diffusion to concrete cracking. Mass diffusion, Faraday's law and the Extended Finite Element Method (XFEM) were used to simulate chloride diffusion, mass loss from steel corrosion and corrosion product expansion and concrete cover cracking simultaneously, while the pressure due to the tensile stress generated by corrosion product was idealized as radial displacements. Obtained results show an increasing chloride concentration with time, but reduction with depth of penetration, while an obvious crack pattern was obtained.
Probabilistic failure modelling of reinforced concrete structures subjected to chloride penetration
International Journal of Advanced Structural Engineering, 2012
Structural durability is an important criterion that must be evaluated for every type of structure. Concerning reinforced concrete members, chloride diffusion process is widely used to evaluate durability, especially when these structures are constructed in aggressive atmospheres. The chloride ingress triggers the corrosion of reinforcements; therefore, by modelling this phenomenon, the corrosion process can be better evaluated as well as the structural durability. The corrosion begins when a threshold level of chloride concentration is reached at the steel bars of reinforcements. Despite the robustness of several models proposed in literature, deterministic approaches fail to predict accurately the corrosion time initiation due the inherent randomness observed in this process. In this regard, structural durability can be more realistically represented using probabilistic approaches. This paper addresses the analyses of probabilistic corrosion time initiation in reinforced concrete ...
Journal of Building Pathology and Rehabilitation, 2017
Nowadays an amount of reinforced concrete structures are presenting problems related with corrosion of reinforcement, mainly that induced by chloride ions. So, many studies are being accomplished to predict the necessary time for chloride ions reach the reinforcement, beginning the propagation of corrosive process. In this paper, three models were selected for analysis to determine their ability in properly predicting the chloride penetration in concrete structures: the solution of 2nd Fick's Law, the complete solution of 2nd Fick's Law, considering the variation of diffusion coefficient and the superficial concentration of chlorides in time; and a model proposed. Analysis of the formulations principles and assessment and applicability of equations were made, taking into account the adequate choice of parameters and variables involved, the difficulty to obtain these parameters, and if the models represent properly the natural phenomena. In order to contribute with the service life prediction of the structures when inserted in saline environments, a mathematical model was developed based in a Focus Groups analysis. Some of the main characteristics of the proposed model are the logic applied for its development and the application easiness. This model was applied in a case study to verify the answer in relation to chloride penetration in some points of a reinforced concrete structure inserted in a saline area. The behavior of the model was consistent with the results of experimental investigations accomplished by other researchers.
Development of Simulation Model of Chloride Ion Transportation in Cracked Concrete
Journal of Advanced Concrete Technology, 2005
Chloride-induced deterioration is the most important deterioration phenomenon in reinforced concrete structures in marine environments. When a crack occurs in cover concrete, it may initiate and accelerate corrosion of steel reinforcements embedded in the concrete. The performance of the reinforced concrete structure may subsequently decrease even in the early stage of its service life. With the aim to clarify the mechanism of chloride-induced deterioration, this paper reports the results of experimental investigation on chloride ion transportation in cracked concrete and proposes a simulation model for chloride ion transportation in cracked concrete. The zone affected by cracking was treated as the exposed surface of concrete in the proposed model, where chloride transportation was assumed to be governed by the concentration of the chloride ion solution in the crack. In addition, the effects of the crack width and an apparent diffusion coefficient through the cracks on chloride ion transportation were numerically investigated and the applicability of the proposed model was discussed.
Assessment and Modeling of Qualitative Damage-Induced Chloride Diffusivity on Concrete Durability
International Congress on Durability of Concrete, Trondheim, Norway, 2012
Concrete Durability is associated with many controlling factors such as the quality of concrete used, quality of workmanship, and the operational maintenance. However there are some other factors which are beyond control, including environmental impact such as that imparted by the ingress of chloride into concrete which promote premature deterioration and lessen the useful service life of the structures. Although environmental issues appear to be beyond our control especially for those building and structures adjacent to the shore and in the vicinity of marine environment, yet one can make it hard for the chloride to penetrate reinforce concrete structures by controlling the quality of concrete in terms of proper placement and curing as well as maintaining adequate cover. Prediction of the useful life of a structure depends on the adopted diffusivity used to model the transient problem of chloride migration into the structures. In literatures, however such modeling is based on ideal and non-damaged diffusivity which is rare to be realistic as even under service loading part of the structures are subjected to damage in the tension zone especially for flexural members. It is the purpose of this paper to make comparative assessment of the useful life by considering damaged and undamaged diffusivity. Three cases will be contrasted that of undamaged, uniform damage and linear damage depicting damage in flexural member. A COMSOL package software is used to model the chloride ingress using fink's law with nonlinear diffusivity after incorporating damage. It has been found that the useful life reduced by more than half as compared to the ideal case of using undamaged diffusivity. This calls for different specification of good quality concrete to account for the induced damaged and to prolong the life of the structures as intended.
Meso-scale simulation of chloride ingress in cracked concrete
A three-dimensional meso-scale lattice model for simulating chloride diffusion in uncracked and cracked concrete is presented. Both the fracture and the chloride diffusion simulations consider concrete as a three-phase composite, consisting of coarse aggregates, mortar matrix and the interface. Based on Fick's second law, a discrete formulation using the lattice approach is proposed. Different phases are assigned with different properties (tensile strength, diffusion coefficient) in order to simulate the fracture and ingress behaviour. Also, a temperature dependent diffusion coefficient is taken into account. The effects of temperature and concrete heterogeneity on the chloride penetration are evaluated and discussed. In order to model the influence of cracking on chloride ingress, a relation between the crack width and the diffusion coefficient is adopted. Also in the case of cracked concrete, the effect of temperature is evaluated and discussed. This study shows that concrete temperature and composition have a marked effect on chloride ingress in concrete. In cracked concrete, although these factors also have an influence, the most significant is the effect of cracking. It is concluded that the lattice model can be successfully applied to model chloride diffusion in uncracked and cracked concrete on the meso-scale. 1.