Chloride-induced Deterioration Research Articles

Cyclic shear testing of artificially corroded reinforced concrete short circular piers

Chloride-induced deterioration of reinforced concrete (RC) structures is an increasingly vital topic among asset management and structural maintenance fields, as many RC bridges and other structures are reaching the end of their initial design lives. Deterioration of the transverse reinforcement in RC piers leads to the direct loss of shear and confinement-related mechanical properties as degradation advances with time. This research investigates the seismic response of fourteen short RC circular piers subjected to artificial chloride-induced corrosion. Each pier is designed to trigger a shear-dominated failure and artificially corroded at two current densities. A maximum average mass loss of 10.5% and 43.0% was measured in the longitudinal and spiral reinforcement, respectively. The influence of confinement effectiveness, spiral diameter, and aspect ratio on the rate of shear capacity degradation are included as test parameters in this study. Results indicate that shear deformation begins to govern performance at moderate to severe deterioration, which precedes the onset of brittle shear-dominated failure modes. Ultimate deflection is more adversely affected by increasing corrosion than all other measured properties, with a maximum observed reduction of 70.9% compared to a maximum 37.5% reduction observed in peak shear capacity. Several existing theoretical models are introduced and evaluated on their ability to predict the shear capacity of the experimental tests. Based on the results, those models directly evaluating the circular section without needing an equivalent section transformation offer the most accurate and reliable predictions.

Chloride-induced concrete deterioration monitoring using advanced ultrasonic pulse wave analysis based on convolutional neural network

This research explores the potential of deep learning techniques, specifically the convolutional neural network (CNN) architecture, for classifying concrete crack levels based on an acceptable threshold of concrete cracking. The classification model utilizes ultrasonic pulse wave data collected from concrete cube specimens before and after undergoing an accelerated corrosion process. A total of 108 concrete specimens, representing three different mix designs, three corrosion levels, and four concrete cover thicknesses, were utilized in this study. The collected data was employed to train CNN models, specifically leveraging the GoogLeNet and SqueezeNet architectures. Various input sampling rates, input lengths, and hyperparameters were explored to determine the optimal training setup, yielding the best prediction performance. The results demonstrate that the optimized models achieve an 84% accuracy in distinguishing cracks below and above the acceptable threshold. Therefore, it can be concluded that the CNN method holds potential for in-situ sensors aimed at monitoring chloride-induced deterioration in concrete structures.

Stochastic Multiphasic Multivariate State-Based Degradation and Maintenance Meta-Models for RC Structures Subject to Chloride Ingress

The objective of this paper is to propose tools for the lifecycle management of infrastructure by showing the slow degradation processes for which inspection data are accessible, especially the data obtained from non-destructive testing (NDT) and structural health monitoring (SHM). One major characteristic of these degradation processes is their multiphasic nature; consequently, they can be discretised into different phases with specific physical kinematics where specific maintenance actions and measurement techniques can be performed. Within this framework, we propose implementing a degradation meta-modelling approach fed with measurements (NDT, SHM). This approach is based on state-dependent stochastic processes for modelling the degradation and maintenance of reinforced concrete structures that are subjected to chloride-induced deterioration. The benefit of using multiphasic degradation meta-models in the lifecycle management of infrastructure is illustrated through numerical examples that include single and multi-action management policies.

Seismic Fragility Analysis of the Aging RC Columns under the Combined Action of Freeze–Thaw Cycles and Chloride-Induced Corrosion

The combined action of freeze–thaw cycles and chloride-induced corrosion are generally recognized as one of the main causes of the degradation of the mechanical properties and seismic performance of reinforced concrete (RC) structures in the northern frozen coastal regions. To investigate the degradation mechanisms of the seismic performance of RC columns subjected to the combined action of freeze–thaw cycles and chloride-induced corrosion, the impact of freeze–thaw cycles on the chloride diffusion coefficient of concrete was studied through concrete deterioration tests and theoretical analysis. This paper proposed a time-dependent deterioration model for RC columns, which is suitable to consider the combined action of freeze–thaw cycles and chloride-induced deterioration. The proposed deterioration model could be applied to the investigations of time-dependent seismic performance and the seismic fragility of RC columns. Based on the established deterioration model, this paper proposed a time-dependent seismic fragility analysis framework for the aging RC columns, considering the combined action of freeze–thaw cycles and chloride-induced corrosion. In addition, a representative three-span RC continuous T-shaped girder bridge that is located in the high-latitude northern frozen coastal regions of China was taken as the case study, and the time-dependent seismic fragility analysis of RC columns was conducted considering the involved uncertainties in geometric parameters, the deterioration mechanisms of the materials, and ground motions. The time-dependent seismic fragility curves of RC columns were obtained at different service time points. The results indicated that the combined action of freeze–thaw cycles and chloride-induced deterioration had a significant influence on the time-dependent seismic responses of the deteriorating RC columns. Under the combined action of freeze–thaw cycles and chloride-induced corrosion, when the RC bridge was in service for 75 years, the stirrup strength decreased by 3.88% and the cross-sectional area decreased by 30.03%. The peak stress of the confined concrete decreased by 52.1% and its peak strain increased by 12.2 times, respectively. Moreover, the time-dependent seismic fragilities of the aging RC columns under different damage states exhibited a nonlinear increase as the service life increased.

Probabilistic analysis of climate change impact on chloride-induced deterioration of reinforced concrete considering Nordic climate

The impact of climate change on the deterioration of reinforced concrete elements have been frequently highlighted as worthy of investigation. This article addresses this important issue by presenting a time-variant reliability analysis to assess the effect of climate change on four limit states; the probabilities of corrosion initiation, crack initiation, severe cracking, and failure of a simply supported beam built in 2020 and exposed to chloride-induced corrosion. The historical and future climate conditions (as projected by three different emission scenarios) for different climate zones in Sweden are considered, including subarctic conditions where the impact of climate change may lead to large increases in temperature. The probabilities of all limit states are found to be: 1) higher for scenarios with higher GHG emissions and 2) higher for southern than for northern climate zones. However, the end-of-century impact of climate change on the probabilities of reaching the different limit states is found to be higher for northern than for southern climate zones. At 2100, the impact of climate change on the probability of failure can reach up to an increase of 123% for the northernmost zone. It is also noted that the end-of-century impact on the probability of failure is significantly higher (ranging from 3.5–4.9 times higher) than on the other limit states in all climate scenarios.

Electrical Resistivity Measurements for Nondestructive Evaluation of Chloride-Induced Deterioration of Reinforced Concrete-A Review.

The objective of this study is to review, evaluate, and compare the existing research and practices on electrical resistivity as a nondestructive technique in evaluating chloride-induced deterioration of reinforced concrete elements in buildings and civil infrastructure systems. First, this paper summarizes the different measurement techniques for gathering electrical resistivity (ER) values on concrete. Second, comparison analyses are performed to review the correlation of ER to different parameters representing corrosive environment and activity of steel corrosion in concrete, such as degree of water saturation, chloride penetration and diffusivity, and corrosion rate. In addition, this research enumerates and individually discusses the different environmental and interference factors that are not related to the electrochemical process of steel corrosion in concrete but directly affect the ER measurements, including temperature, the presence of steel reinforcement, cracks and delamination defects, specimen geometry, and concrete composition. Lastly and most importantly, discussions are made to determine the current gap of knowledge, to improve the utilization of this method in field and laboratory measurements, and future research.

Failure mode of deteriorated concrete tunnel sections under subsidence and localised shear

It is frequently reported that groundwater containing salt flowing into underground reinforced concrete structures results in steel reinforcement corrosion. However, little has been done to study the impact of such chloride-induced deterioration on structural performance when an external load acts on the underground structure, such as ground subsidence or the movement related to faults. In this study, structural experiments and finite-element analysis of the interaction between an underground structure and the ground were undertaken to clarify the failure modes and verify the numerical analysis. The failure behaviour of an underground structure with corroded steel subject to ground displacements was then examined analytically. It is concluded from the study that chloride-induced deterioration can impair the durability of an underground structure, making it difficult to maintain the inner space, and the failure mode is related to the location of the steel corrosion, which can change the direction of the shear zone in the peripheral ground.

Concurrent modelling of carbonation and chloride-induced deterioration and uncertainty treatment in aging bridge fragility assessment

Significant research efforts have been recently invested towards the evaluation of chloride-induced deterioration effects on the seismic vulnerability of aging highway bridges. Furthermore, when located in coastal cities with increased urbanisation or near shipyards, bridge structures may also be subjected to potentially high levels of carbon dioxide emissions. Consequently, the physicochemical process resulting from simultaneous ingress of chlorides and concrete carbonation may lead to accelerated corrosion deterioration of reinforced concrete components, as evidenced in past experimental tests. Nevertheless, little attention has been paid towards modelling this joint influence of chloride and carbonation-induced corrosion deterioration on strength degradation of bridge components. The present study proposes a numerical iterative scheme to evaluate the simultaneous impact of these deterioration mechanisms on the seismic response and bridge fragility. The proposed framework is demonstrated on a case-study multi-span continuous steel girder bridge in Central and Southeastern United States. Results reveal a considerable influence on the corrosion initiation time and seismic vulnerability under the concurrent carbonation and chloride ingress. Furthermore, this study also conducts a systematic exploration of uncertainty at different stages of the deterioration process. This exercise helps provide recommendations on balancing between computational complexity and accuracy of seismic fragility predictions.

Time-dependent Seismic Fragility Assessment for Aging Highway Bridges Subject to Non-uniform Chloride-induced Corrosion

ABSTRACT This paper proposes an alternative time-dependent seismic fragility assessment framework considering the variable correlation of structural random parameters for aging highway bridges subject to non-uniform chloride-induced corrosion attacks. The proposed systematic framework is implemented to perform a probabilistic time-dependent seismic fragility assessment for a typical multi-span reinforced concrete continuous girder (MSRCCG) bridge. Effects of non-uniform chloride-induced deterioration on the time-evolving seismic capacity, seismic demand of reinforced concrete (RC) columns, and the time-dependent seismic fragility of the case-study bridge are investigated using nonlinear sectional moment-curvature and nonlinear time history analysis. Furthermore, this paper performs comparative studies to investigate the influence of variable correlation of structural random parameters on the time-variant seismic capacity, seismic demand of RC columns, and time-dependent seismic fragility of the case-study bridge. The results indicate the following conclusions: (1) Non-uniform chloride-induced corrosion may change the vulnerable position and the damage mechanisms of RC columns; (2) Due to non-uniform chloride-induced deterioration, the flexural capacity and curvature ductility of RC columns may exhibit a nonlinear reduction, while there is a nonlinear accelerated growth of time-dependent seismic fragility for aging highway bridges along their service lives; (3) The time-variant seismic capacity (i.e., the flexural capacity and curvature ductility) and seismic demand of RC columns tends to have a certain reduction and increase by ignoring the variable correlation of structural random parameters, respectively; and (4) The time-dependent seismic vulnerabilities of aging highway bridges may be overestimated by ignoring the variable correlation of structural random parameters.

Layered Double Hydroxides Precursor as Chloride Inhibitor: Synthesis, Characterization, Assessment of Chloride Adsorption Performance.

In this study, the chloride adsorption behaviors of CaAl-Cl LDH precursors with various Ca:Al ratios were investigated. The optimal chloride ion removal rate was 87.06% due to the formation of hydrocalumite. The chloride adsorption products of CaAl-Cl LDH precursors were further characterized by X-ray diffraction analysis and atomic structure analysis, the adsorption mechanism was considered to be co-precipitate process. The chloride adsorption behaviors of cementitious materials blended with CaAl-Cl LDH precursors were further investigated. Leaching test according to Test Code for Hydraulic Concrete (SL352-2006) was performed to testify the stability of chloride ions in the mortar. The results show that more than 98.3% chloride ions were immobilized in cement mortar blended with CaAl-Cl LDH precursor and cannot be easily released again. The inhibition performance of steel in the electrolytes with/without CaAl LDH precursor was investigated by using electrochemical measurements. The results indicate that CaAl LDH precursor can effectively protect the passive film on steel surface by chloride adsorption. Considering the high anion exchange capacities of the LDHs, synthesized chloride adsorbent precursor can be applied as new inhibitors blended in cementitious materials to prevent the chloride-induced deterioration. Moreover, the application of chloride adsorption on CaAl-Cl LDH could also be of interest for the application of seawater blended concrete.

Seismic Retrofit Screening of Existing Highway Bridges With Consideration of Chloride-Induced Deterioration: A Bayesian Belief Network Model

Vulnerability of seismically deficient bridges, coupled with their ageing and deterioration, pose significant threat to safety, integrity and functionality of the highway network that could result in significant risks to public safety, traffic disruption, and socio-economic impacts. Given the limited funds available for bridge retrofit, there is a need for an effective management strategy that will enable engineers to identify and prioritise the high-risk bridges for detailed seismic evaluation and retrofit. A practical risk-based preliminary seismic screening technique is proposed in this paper that enables to develop a ranking or prioritization scheme for seismically-deficient bridges. The complex interactions between seismic hazard, bridge vulnerability and consequences of failure are handled in a hierarchical manner. A Bayesian belief network based modelling technique is used to aggregate through the hierarchy and generate risk indices by accounting for chloride-induced corrosion deterioration mechanisms. The efficacy of the proposed method is illustrated on two existing bridges that are assumed to be located in high seismic zones and designed under different standards concerning their structural safety under seismic loads and durability performance.

ANALYSIS OF DETERIORATION IN REINFORCED CONCRETE BRIDGE GIRDERS DAMAGED BY CHLORIDE DETERIORATION AND FATIGUE

The subject of this research was a concrete T-girder bridge which had been exposed for 40 years to the sub-tropical archipelago environment off the east coast of Okinawa, with large amounts of windblown salt, high temperatures and high humidity, a harsh environment for salt damage and steel corrosion. It had suffered damage in the forms of 1) concrete spalling due to reinforcing bar corrosion, 2) internal loss of cross section and severance in internal reinforcing bars, and was therefore removed. Various tests and inspections were applied to analyze the state of deterioration of a real salt-damaged bridge, with the aim of providing technical reference material of use in formulating appropriate maintenance management methods. Distant visual inspection was performed prior to removal of the girder. After the removal, close visual inspection and non-distractive inspections were performed. Compressive strength, elastic modulus and chloride ion content of the concrete were measured. Corrosion of reinforcing bar was observed after chipping the concrete. Chloride-induced deterioration inside the concrete and competence of non-destructive inspection for the deterioration were studied. Static loading test and fatigue-test were performed.

3F22 STUDY ON THE AREA OF CAUTION FOR CHLORIDE ATTACK IN SUBWAY BOX TYPE TUNNELS(Condition Monitoring-Infrastructure)

Tokyo Metro has been studying chloride-induced deterioration of subway tunnels by investigating tunnel bodies and taking countermeasure methods. From the resent results of the study, it had become clear that chloride-induced deterioration of subway tunnels almost always occurs at boundaries of areas leaking with chloride. For this reason, we studied potential areas that have chloride-induced deterioration in cut&cover tunnels by investigating the positional relation between tidal rivers and chloride leakage areas. As the result, it was found that the areas are 50m or more below the edges of tidal rivers. Then, seen from the viewpoint of advection-diffusion of chloride in the underground water, we verified the validity of the result by underground density flow analyses.

Chloride adsorption by calcined layered double hydroxides in hardened Portland cement paste

This study investigated the feasibility of using calcined layered double hydroxides (CLDHs) to prevent chloride-induced deterioration in reinforced concrete. CLDHs not only adsorbed chloride ions in aqueous solution with a memory effect but also had a much higher binding capacity than the original layered double hydroxides (LDHs) in the cement matrix. We investigated this adsorption in hardened cement paste in batch cultures to determine adsorption isotherms. The measured and theoretical binding capacities (153 mg g−1 and 257 mg g−1, respectively) of the CLDHs were comparable to the theoretical capacity of Friedel's salt (2 mol mol−1 or 121 mg g−1), which belongs to the LDH family among cementitious phases. We simulated chloride adsorption by CLDHs through the cement matrix using the Fickian model and compared the simulation result to the X-ray fluorescence (XRF) chlorine map. Based on our results, it is proposed that the adsorption process is governed by the chloride transport through the cement matrix; this process differs from that in an aqueous solution. X-ray diffraction (XRD) analysis showed that the CLDH rebuilds the layered structure in a cementitious environment, thereby demonstrating the feasibility of applying CLDHs to the cement and concrete industries.

Numerically and Experimentally Based Reliability Assessment of a Concrete Bridge Subjected to Chloride-Induced Deterioration

AbstractMaintaining an adequate safety level in concrete bridges under gradual degradation due to traffic and environmental actions is not only an expensive task, but also filled with some level of uncertainty. Degradation in itself is not easily quantifiable because numerous aspects reduce the load-bearing capacity of a concrete bridge. Furthermore, the effects of preventive maintenance and rehabilitation actions are difficult to predict. Chloride ion ingress is an important aspect of durability design and maintenance, especially in regions where winter salt is commonly applied for traffic safety. This paper introduces a feasible approach to analyze the effects of chloride-induced deterioration on the overall safety level, which is validated by the application to a real highway bridge, which was demolished after 38 years of service. Concrete samples were extracted from this bridge and chemical analyses were performed to determine the chloride concentration profile in the concrete. Once the present chlori...

Enhanced Long-Term Resistance of Concrete with Marine Sessile Organisms to Chloride Ion Penetration

Reinforced concrete (RC) structures in marine environments are generally affected by harsh marine environmental actions, resulting in early performance degradation mainly due to chloride-induced deterioration. In such conditions, corrosion of rebar progresses rapidly, and also the cross-sectional area of rebar is reduced and consequently structural performance of RC structures will be degraded. In contrast, the surface of concrete structures is often covered with many marine sessile organisms under marine tidal and submerged conditions. These marine sessile organisms have been empirically known to enhance the durability of concrete though the effectiveness is not appropriately evaluated. This paper describes the long-term resistance of concrete with marine sessile organisms to chloride ion penetration in concrete. The effect and its sustainability of marine sessile organisms on chloride ion penetration in concrete were investigated through field exposure test and laboratory test. From the test results, the basal membrane, which is a matrix of marine sessile organisms, adheres to concrete strongly on a long-term basis though some gaps between concrete and the basal membrane can be observed. In addition, experimental results and simplified simulation clarified that the attachment of marine sessile organisms can enhance the long-term resistance of concrete to chloride ion penetration.

Microstructural analysis of plain and reinforced mortars under chloride-induced deterioration

This paper reports the results of microstructural analysis of plain and steel-reinforced mortar specimens deteriorated by chlorides that were admixed or introduced through chloride ingress. The electrical properties of mortars were measured and their microstructural characteristics were investigated using quantitative image analysis techniques. The influence of chloride ions on mortar microstructure are discussed in terms of hydration and corrosion products. The research reveals that chlorides will induce changes in the chemical compositions and morphology of cement hydration products, and thereby exert influence on ion transport in the mortar specimens. The electrical properties of plain and reinforced mortars are not only related to the presence of chlorides in the pore system but are also influenced by the pore structure characteristics. The cementitious matrix undergoes certain alterations in conditions of the combined effects of: cement hydration, chloride ion transport and chemical binding mechanisms. To this end the pore structure characteristics appeared to be a significantly contributing factor in the process of chloride-induced corrosion in reinforced cement-based materials.

Development of Simulation Model of Chloride Ion Transportation in Cracked Concrete

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.