Corrosion-induced Concrete Cracking Research Articles

An integrated material-structural analysis of prestress concrete affected by corrosion of non-prestressed reinforcement

Corrosion-induced concrete cracking is a significant stage of structural deterioration in prestressed concrete (PC) structures. Most current research predominantly focuses on the corrosion of prestressed steel strands, while paying limited attention to the study of non-prestressed reinforcement corrosion. In this study, an integrated material-structural numerical approach was developed to simulate corroded PC beams, considering corrosion products migration in pores and cracks. The cracking patterns and prestress losses obtained from the simulation results agreed well with experimental observations. Subsequently, using the proposed numerical approach, the interaction mechanism of the prestress level and reinforcement corrosion was investigated. The simulation results indicated that corrosion of longitudinal reinforcement leads to cross-sectional damage, causing the redistribution of stress across the section and increasing long-term deformation, ultimately resulting in prestress losses. Meanwhile, stirrup corrosion leads to an initial increase in prestress due to expansion forces when the degree of corrosion is not so high, but finally it will also lead to a degradation of mechanical performance.

Creep Effect on Time to Corrosion-Induced Cracking of Concrete Cover

AbstractThis paper presents an innovative method to include creep deformations in the prediction of time to corrosion-induced cover cracking. Using experimental results, creep and cracking criteria used in this method are verified. It is argued in the paper that the cover cracking problem under corrosion is close to a relaxation problem and the conventional creep formulations based on the effective elastic modulus cannot be adopted. It is found in the paper that accurate consideration of creep deformation would lead to about 30–40% longer time to cover cracking when compared to no consideration of creep deformations whilst for the currently practiced methods, the time can be up to 200% longer, which is unconservative in predicting time to cover cracking. Results in this paper open the debate on modelling of creep in the analysis of corrosion-affected structures and serve as an important step towards the accurate prediction of corrosion-induced concrete cracking.

Simulation of time-varying corrosion rate of rebars and corrosion-induced cracks in reinforced concrete structures subjected to chloride contamination

Corrosion of rebars and consequent corrosion-induced cracks significantly deteriorate durability and serviceability of reinforced concrete (RC) structures. This paper presents a time-dependent numerical model to simulate the entire corrosion process from initiation stage to crack propagation stage and consider the effect of cracks on the development of corrosion current density. Chloride transport model was implemented to determine evolution of corroded area in cross-section of rebars, while two configurations of corroded length along the bar axis was considered: (1) the entire length of rebar was simultaneously corroded and (2) the corroded length evolved gradually from the middle of the bar towards its two ends. Corrosion current density was calculated based on microcell and macrocell electrochemical mechanisms, while a mechanical model was established to simulate corrosion-induced concrete cracking. The results showed that the proposed numerical model was capable of predicting natural corrosion process and consequent crack propagation in RC structures subjected to chloride attack. When cracks developed through the concrete cover, corroded area spread faster, microcell and macrocell current densities increased, and the rust layer became more rounded.

Three-Dimensional Finite Element Modelling for Prediction Corrosion Induced Cracking Damaged in Reinforced Concrete Beam

The quality and condition of the reinforced concrete structure is critical, particularly in high-rise buildings where the danger of service life failure is extremely high. Usually, certain structures collapse as a result of cracks and spreading caused by corrosion. Due to this reason, there is a requirement for software program that can promptly measure and evaluate the strength, growth, and longevity of the structure. Researchers use Finite Element Modelling (FEM), a reliable approach to foresee the deterioration and fracturing of structures. The application of finite element modelling in determining the remaining strength of damaged components can provide crucial data, which is particularly relevant for engineers in real-world scenarios. Moreover, it has the ability to replicate the cracking caused by corrosion in reinforced concrete elements. A corrosion-induced cracking model is suggested to be included into a three-dimensional plane-stress finite element model. The cracking model provides an indication of the extent of corrosion-induced damage in the concrete, allowing for the study of strength and behavioural changes. The effect of corrosion-induced cracking in a thick wall cylinder model will be simulated by the finite element model in order to identify and analyse the cracks caused by corrosion in the concrete cover. A corrosion-induced cracking experiment will be conducted with two different cover thicknesses and reinforcement using the Midas FEA commercial software to create a three-dimensional model. There is a slight discrepancy between the numerical analysis modelling and the analytical approach in terms of the crack's initiation and propagation, mostly resulting from variations in modelling assumptions, methods, and parameters. This disagreement arises when comparing the numerical analysis model with the previously published work. Nevertheless, the numerical model may be used to simulate both crack propagation and the critical pressure needed to produce corrosion-induced concrete cover cracking.

A two-phased modelling approach for corrosion-induced concrete cracking and bond deterioration in reinforced concrete

Bond deterioration is one of the major consequences of reinforcement corrosion in reinforced concrete (RC) structures. In this paper, a two-phased numerical modelling approach is presented that aims to determine the constitutive behaviour (bond–slip) at the reinforcement-concrete interface at a certain corrosion level. The novelty of the approach is that it consists of a crack model and a bond model, and that the flow of corrosion products into the pores and corrosion-induced cracks as well as the effect of the bonded length and concrete cover are taken into account in the 2D crack model. The resulting expansion of corrosion products from the crack model is used as input in the 3D bond model. The combination of both models leads to a procedure that balances computational time and modelling detail. The model is validated on a substantial amount of experimental pull-out test results. A good agreement is obtained between the experimental data and the models for different corrosion levels in terms of crack width, crack pattern, corrosion-induced bond loss, and failure mode.

Numerical study on the effects of non-uniform corrosion and confinement conditions on the bond performance of RC beams

A 3D model is established to simulate the bond performance of corroded RC beams, in which the non-uniform corrosion of tensile reinforcement and confinement conditions (characterized by the thickness-diameter ratios of 1.9–3.8 and stirrup confinement index of 0–8.3%) are investigated. In the 3D numerical model, fine modeling was adopted to consider the influences of corrosion on the steel-concrete interface and the non-uniform corrosion was considered by separating the tensile bars into two parts with inconsistent diameter loss. Meanwhile, a two-stage numerical analysis method was utilized, to reflect the corrosion-induced concrete cracking by applying forced displacement and subsequently analyzed their flexural bond performance. In comparison to the existing experiments, the proposed 3D numerical model is proved to be reasonable. In addition, the simulation results show that the increment of the (residual) bond strength generated by the increasing thickness-diameter ratio increases with the mass loss rate, while the increases of stirrup confinement index cause much more increases in the (residual) bond strength for the corroded RC beams than the un-corroded beams. Furthermore, a bond stress-slip relationship is proposed taking the non-uniform corrosion and confinement conditions into account, which correlates well with the experiments.

A multi-phase-field framework for non-uniform corrosion and corrosion-induced concrete cracking

Predicting the failure of reinforced concrete structures due to rebar corrosion is significant in maintaining the service life of concrete structures. This paper presents a multi-phase-field framework at the mesoscale to investigate the time-dependent process of non-uniform corrosion and concrete cracking. The evolution of the corrosion morphology and cracking pattern were described by a phase field corrosion model and a phase field regularized cohesive zone model, respectively. The diffusion-corrosion coupling and corrosion-fracture coupling were achieved by corrosion-induced current density and expansion-induced strain, respectively. The diffusion-crack interaction and the rust-concrete confinement were included in the model. The numerical results of each model component were compared with three separate experimental data. The effects of interface thickness and length scale on corrosion and fracture behaviors were investigated. Two numerical experiments were conducted to demonstrate the feasibility of studying the evolution characteristics of corrosion and cracking under localized corrosion and non-uniform corrosion in 3D.

Investigation of the filling-overflow behavior of corrosion products in reinforced mortar

The investigation of the filling-overflow behavior of corrosion products in concrete is important for accurately predicting corrosion-induced concrete cover cracking. This paper utilizes the ethylene diamine tetra acetic acid (EDTA) titration method to quantitatively study the iron content in each zone of corroded reinforced mortar specimens. Based on this, the proportion and distribution of corrosion products are analyzed. Results show that approximately 50% of the corrosion products are transported to the mortar and corrosion products show a transport pattern to the surrounding low-concentration area in mortar. The direction of ion invasion on the mortar specimen does not exhibit a significant impact on the transport of corrosion products, while both the geometric size and quality of the mortar specimen affect the transport of corrosion products. Furthermore, the proposed method employs EDTA titration to quantify the filling and overflow of corrosion products, providing a valuable approach for further experimental research.

Multi-peak nonuniform model of rust distribution and corrosion-induced concrete cracking in reinforced concrete slabs

Corrosion-induced concrete cracking is of importance in evaluating service life of reinforced concrete (RC) slabs. Rust distribution and steel bar configuration are two of the most parameters affecting not only internal and surface crack patterns, but also evolution of surface crack width. In this paper, a mathematical model based on AsymmetricalGeneralisedvonMises distribution (AGvM model) was proposed to simulate multi-peak asymmetrical nonuniform rust layer around the steel bar's circumference. Besides, an advanced 3D finite element (FE) model was developed incorporating rust distribution obtained from the AGvM model to simulate corrosion-induced concrete cracking. An experimental programme of six RC slabs with three different steel bar configurations and two corrosion levels was conducted to validate the AGvM and the FE models. As a result, it showed that the proposed AGvM model was capable of simulating rust distribution around the steel bar better than the other six existing mathematical models, especially when the rust layer had two peaks and its distribution was highly asymmetrical. Moreover, the 3D FE model could reasonably predict internal and surface crack patterns, as well as evolution of surface crack width of RC slabs. Based on the test results and numerical models, effects of steel bar configurations on corrosion-induced concrete cracking were discussed.

Time-dependent nonuniform numerical model of corrosion process and consequent corrosion-induced concrete cracking under chloride attack

Corrosion of steel bars and consequent concrete cracking are complicated processes and they mutually affect one another. In this study, a 3D time-dependent numerical model was developed to simulate localised corrosion in both circumferential and longitudinal directions, incorporating effects of nonuniform corrosion-induced cracks. Time-dependent evolution of corroded area in the circumferential direction around the steel bar was calculated as a function of chloride concentration, while two configurations of corroded length along the steel bar axis were simulated: (1) the entire length of steel bar was corroded at the same time and (2) the corroded length progressively developed from the middle of the bar towards its two ends. Microcell and macrocell mechanisms were applied to determine the total corrosion rate. Consequently, a finite element model was developed to simulate nonuniform corrosion-induced concrete cracking. It was found that once a vertical crack propagated through the concrete cover, not only did the corroded area spread faster, microcell and macrocell current densities also substantially increased, and the shape of corroded depth became more rounded.

Characterization of OFDR distributed optical fiber for crack monitoring considering fiber-coating interfacial slip

An analytical crack-strain transfer model considering interfacial bond-slip between optical fiber and fiber coating is proposed and experimentally validated for crack monitoring of structures. Interfacial shear stress-slip relationship between the optical fiber and fiber coating was determined by using pull-out tests, and a simplified trilinear three-stage interfacial shear stress-slip model was proposed. The model is incorporated into the development of a crack-strain transfer model between the structural substrate and the optical fiber, and the fiber strain distribution is analytically obtained and compared with the strain distribution as perfect bond is assumed between the fiber and fiber coating. Experiments were also conducted to validate the crack-strain transfer model by continuously monitoring corrosion-induced concrete cracking with OFDR distributed optical fiber. Compared with strain transfer models proposed by other researchers in the literature and perfect bond model, the crack-strain transfer model considering interfacial shear stress-slip mechanism between fiber and fiber coating agrees well with experimental results, especially for large crack monitoring.

Developing a three-dimensional finite element analysis approach to simulate corrosion-induced concrete cracking in reinforced concrete beams

Corrosion-induced concrete cracking is a significant stage of structural deterioration in reinforced concrete (RC). Numerous numerical studies were conducted to address this problem, but relatively few considered the effects of stirrups and non-uniform corrosion in three dimensions. In this study, a three-dimensional finite element analysis (FEA) approach was developed to simulate corroded RC beams, considering non-uniform steel corrosion and a detailed arrangement of stirrups. The cracking patterns obtained from the simulation results agreed well with experimental observations. Subsequently, using the proposed FEA approach, the effects of the non-uniform corrosion and stirrup constraints on the cracking pattern were investigated. The simulation results indicated that an RC structure under non-uniform corrosion showed more severe cracking and reached the serviceability limit state earlier. The stirrups limited the propagation of the corrosion-induced cracks, but the constraint weakened with increasing distance from the location of the stirrups.

Meso-scale phase field modelling of reinforced concrete structures subjected to corrosion of multiple reinforcements

Corrosion-induced concrete cover cracking is one of major deterioration mechanisms for reinforced concrete (RC) structures. Concrete cracking caused by corrosion of multiple reinforcements at the meso-scale involves complex toughening mechanism, stress redistribution and crack interaction. It brings significant challenge to accurately predicting the cover cracking which, in most cases, represents a critical stage of serviceability. This paper aims to develop a meso-scale phase filed model for concrete cover cracking induced by corrosion of multiple reinforcements. Concrete is treated as a three-phase heterogeneous material, consisting of aggregates, mortar and interfacial transition zones (ITZ). The developed method is implemented into ABAQUS explicit regime through an in-house VUEL subroutine. The crack patterns and crack width development of concrete induced by corrosion are obtained. The model is also verified against experimental results on the crack width development and crack patterns. Further, a parametric study is carried out to investigate the effects of reinforcement spacing, cover thickness, ITZ fracture properties on concrete cover cracking. Some toughening mechanisms including crack deflection, aggregate/mortar bridging and crack bifurcation in concrete have been captured in the model. ITZ fracture properties significantly affects the crack pattern of concrete cover. The developed method enables high fidelity numerical models with up to tens of millions of degrees of freedom (DOFs), and the completed failure processes of concrete cover are well predicted.

Analytical model of corrosion-induced cracks in concrete considering time-varying deformations of layers, mechanical properties of rust

This paper presents an analytical model to simulate the evolution of corrosion-induced cracks in concrete considering the combined effects of time-dependent deformations of layers and mechanical properties of corrosion products applying the principle of equilibrium of force and compatibility of deformations. Stress, strain and deformation in respective layers of corroding steel, rust and uncracked concrete are determined based on elasticity theory, while coupling tensile softening model and elastic modulus reduction is applied to simulate the cracked concrete. Time-varying deformations of four layers and the influence elastic modulus and Poisson’s ratio of rust are considered in force equilibrium and compatibility conditions to determine crack length, stress and strain distributions. It is shown that not only the time-to-surface cracking is shortened, the trend of crack development is also altered if the deformations of layers are considered. A higher elastic modulus results in a faster time for cracks to reach the concrete surface, while a larger Poisson’s ratio would lead to slower propagation of cracks. By analysing the results obtained from the proposed model and test data, a semi-empirical relationship between applied current density and elastic modulus of rust is recommended. This correlation could be used to predict the elastic modulus of rust which is an important parameter in modelling corrosion-induced cracks in concrete.

Meso-scale modeling of concrete cracking induced by 3D corrosion expansion of helical strands

A meso-scale numerical model is established to simulate concrete cracking induced by the three-dimensional (3D) corrosion expansion of helical strands in the present study. A 3D corrosion expansion model is proposed to consider the longitudinal helix shape and transverse flower-like shape of the strand. The concrete in the model is considered as a three-phase composite material consisting of a mortar matrix, aggregate, and interfacial transition zones (ITZ) between the mortar matrix and aggregate. The rationality of the proposed model is validated, and the effects of the space helix structure and the lay length of the strand on corrosion-induced cracking are discussed. The results indicate that considering the space helix structure of a strand can effectively improve the prediction accuracy of strand corrosion-induced concrete cracking. The change in strand lay length has little effect on the critical corrosion loss of the initial damage occurrence. The critical corrosion loss at cover cracking increases with increasing strand lay length, whereas the corrosion-induced crack width decreases with increasing strand lay length.

Corrosion-induced cracking propagation of RC beams subjected to different corrosion methods and load levels

Corrosion-induced concrete cracking is a major phenomenon of structural deterioration, useful to appraise durability of structures in service. In this work, beam specimens subjected to loads were corroded by drying-wetting cycles and the impressed-current accelerated method. Three types of corrosion-induced cracks and the strong constraint effect of stirrups were found. The cracking process was divided into two stages by the appearance of a penetrating crack; the crack length ratio had a leap at the critical time. Accelerated corrosion test results underestimated the cracking damage of natural conditions. Furthermore, the larger load accelerated the formation and propagation of penetrating crack.

Investigation of the effects of multiple and multi-directional reinforcement on corrosion-induced concrete cracking pattern

Reinforced concrete (RC) structures are widely used, yet prone to damage induced by reinforcement corrosion which causes susceptibility of concrete spalling and eventually a reduced serviceable life. The visual inspection has been performed usually for structural assessment, but this does not account for the local interactions between rebars. Consequently, detailed scrutiny is required to consider the effects of various parameters on the initiation and propagation of corrosion-induced cracking. This experimental study considers the effect of multiple and multidirectional rebars on the development of corrosion cracking. Additionally, the effect of the location of corrosion and the change in order of corrosion occurrence is investigated in this research. For this purpose, reinforced concrete panels with unidirectional and multidirectional rebar arrangements and varying cover depth are tested using an accelerated corrosion technique. The results show a significant role of confinement in controlling the widths of cracks provided by both reinforcement arrangements. Moreover, the effect of boundary conditions along with increased confining pressure alters the generation of cracks in a unidirectional reinforcement arrangement. In the absence of enough surrounding concrete, cracks along non-corroding rebars can also form because of the expansion of adjacent corroding rebars. The inclusion of multidirectional reinforcement alters the crack direction and causes cracking along non-corroding rebars. Further, previously generated cracks may close considerably by the pressure from adjacent rebar corrosion. This study also facilitates the comprehension of the impact of influencing factors affecting corrosion cracking in real structures.

Prediction of corrosion-induced concrete cracking under external loading and stirrup constraint

In this study, the corrosion-induced concrete cracking in three concrete beams with stirrups under external loading coupled with accelerated corrosion was investigated. The experimental results reveals that the external loading leads to earlier corrosion-induced concrete cracking. The stirrup constraint was found to have a significant influence on both the distribution and propagation of cracking and the longitudinal corrosion of steel. With quantitatively considering the effects of external loading and stirrups, an analytical model was developed to predict corrosion-induced concrete cracking and the results of which were shown to be in satisfactory agreement with experimental results.

Validation of thick-walled cylinder analogy for modelling corrosion-induced concrete cover cracking

The main objective of this paper is to validate the use of the thick-walled cylinder (TWC) analogy to model corrosion-induced crack propagation in reinforced concrete (RC) structures. The TWC analogy neglects the effects of member geometry to create an idealized axisymmetric stress state. Although this simple approach has been used by many researchers, its suitability to various geometries and reinforcement configurations has not been comprehensively investigated previously. To achieve this goal, four different geometries are modeled using finite element analysis. The finite element models are two-dimensional, and they consist of plane membrane, quadrilateral elements under plane-stress conditions. Corrosion-induced expansion at the rebar/concrete interface is simulated using truss elements subjected to an equivalent thermal load. As a part of this validation, the effect of an adjacent corroding rebar and asymmetry of geometry were also investigated. The results are compared against the analytical solutions found using the TWC analogy. This study found that, in general, the use of the TWC analogy to model corrosion-induced cover cracking is appropriate; however, its limitations are also discussed.

Analytical and Experimental Investigation on Corrosion-Induced Concrete Cracking

Practical experience and observation suggest that corrosion-affected reinforced concrete structures are highly susceptible to cracking. This paper presents an analytical time to corrosion-induced concrete cracking model based on fracture mechanics. The concrete cover load-bearing capacity is proposed and is used as a fracture criterion for concrete cracking. An accelerated corrosion test has been undertaken to produce data on time to corrosion-induced concrete cracking and crack width over time. A comparison between the analytical model and experimental results on time to concrete cracking and on crack width over time shows reasonable agreement. It is found that the distribution and size of the porous zone are non-uniform which is one of the main causes for discrepancy between results. The larger the porous zone is the longer it takes for concrete cover to crack due to corrosion. Although the experimental and model results exhibit similar trend, it is also found that assuming only a single propagating crack in analytical model results in an overestimation of corrosion-induced crack width. The models presented in this paper can serve as useful tool for serviceability and durability assessment of corrosion-affected reinforced concrete structures.