Chloride-induced Reinforcement Corrosion Research Articles

Time-dependent fragility analysis of a nuclear containment structure under internal pressure and chloride-induced corrosion

The prestressed concrete containment structure, serving as the ultimate barrier against nuclear fuel leakage, holds paramount importance in ensuring the uninterrupted operation of nuclear power plants. Particularly in the aftermath of the Fukushima nuclear disaster, the influence of material aging and degradation of containment structures has been emphasized. Consequently, a probabilistic performance assessment of containment structures under chloride-induced corrosion condition is of significant relevance. This study presents a method for time-dependent fragility analysis of nuclear containment structures subjected to internal pressure, considering the effect of chloride-induced corrosion of steel reinforcement. A highly efficient and accurate finite element model with multi-layered shell element is formulated for damage and failure analysis. Furthermore, a corrosion degradation model of reinforced concrete, aligned with the attributes of multi-layered shell elements, is derived to reduce the reduce parameter samples generated by Latin Hypercube sampling technique. Material uncertainties and time-dependent effects are jointly integrated into the finite element analysis process, culminating in the establishment of fragility curves for the containment structure under various service lifetimes. The results indicate that within first 40 years of service, the load-bearing capacity of the containment structure has slightly decreased, while the probabilities of functional and structural failures in the containment structure will significantly increase after 60 years of service.

Corrosion inhibition mechanism of vitamins on steel bars in chloride environments: Experimental analysis and quantum chemical calculation

The inhibition potency of thiamine (VB1), nicotinic acid (VB3), pyridoxine (VB6) and ascorbic acid (VC) against the reinforcement corrosion and their adsorption behavior on the surface of steel bars in chloride environments are studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests. Based on the density functional theory (DFT), quantum chemical calculation is also performed to further reveal the corrosion inhibition mechanism of vitamins at the electronic level. The results indicate that these four kinds of vitamins are proven to be potentially applied as corrosion inhibitors to effectively reduce the risk of chloride-induced reinforcement corrosion in a simulated concrete pore solution with 0.05 M NaCl, and VB6 shows the best corrosion inhibition effect since the bonding stability between its highest occupied molecular orbital (HOMO) and the 3d-orbital of iron is the strongest among these vitamins. Under the experimental conditions of this study, there is a specific concentration value for each vitamin to achieve the optimum corrosion inhibition efficiency (IE%). At this time, VB1 and VB3 act as anodic corrosion inhibitors, while VB6 and VC act as mixed-type corrosion inhibitors. With the increase of vitamin concentration, IE% shows a fluctuating value, which is ascribed to the further aggravated imbalance between the cathode and the anode when the cathodic reaction is inhibited due to the adsorption of polar groups on the steel surface.

Carbon steel electrodes within chloride induced reinforcement corrosion in cracked concrete: Approximation to deterministic system response

AbstractResearch on chloride‐induced corrosion in cracked, reinforced concrete is of steady economic and scientific importance. The ever‐growing amount of reinforced concrete structures in need for maintenance and preservation calls for suitable and reliable methods to assess the current state. The present study demonstrates a specimen design that allows authentic corrosion monitoring, including solely carbon mild steel as working and counter electrodes, singularly cracked concrete as electrolytes and a conservative dismantling of the anodic steel‐concrete interface (SCI) at the end of 180 days of monitoring. The electrochemical features of the evolved specimen narrow down to the textbook behavior of the investigated electrodes according to the electro potential series of metals. The most prominent results are the chloride profiles at depth of rebar along the SCI, the build‐up of driving potential, and the decisive contribution arising from the anodic equilibrium potential. Accordingly, future repair methods should always include observation of the anodic equilibrium potential and their effectiveness is clearly addressed in the course of that value.

Chloride profiles – What do they tell us and how should they be used?

Chloride profiles are used to select concrete compositions for new reinforced concrete structures, evaluate the condition of existing structures, and to predict their remaining service life, all with regard to chloride-induced reinforcement corrosion. They are invaluable tools for improving the sustainability of our infrastructure. We examine what chloride profiles tell us and how they should be used. Through a series of case studies, we establish a list of crucial research questions that provide a direction for future research in this field: What is the contribution of chloride binding to chloride transport? What is the path for chloride transport in concrete? How are our findings on chloride profiles relevant for reinforcement corrosion? We then discuss the implications of the answers to these questions for engineering and mechanistic modelling practices.

Quantifying the impact of parameters of chloride-induced reinforcement corrosion on the GPR signal

The sensitivity of the high-frequency ground penetrating radar (GPR) signal to changes within the reinforced concrete (RC) makes it a valuable tool for corrosion assessment of RC structures. The most important parameters in chloride-induced corrosion are moisture content, chloride content, and reinforcement diameter loss. The objective of this laboratory study was to investigate and quantify the influence of these parameters on the GPR signal. Of particular interest was to determine which of the observed parameters the GPR is most sensitive to. Furthermore, particular emphasis was placed on understanding the influence of corrosion products, which has not met the consensus in the existing literature. The parameters were studied on a total of forty-two specimens where the reflector of the GPR waves was the reinforcement embedded in the concrete specimen. Based on the experimental data, values of normalized amplitude related to the evaluation of corrosion by GPR were proposed.

Spatial Distribution of Corrosion Products Influenced by the Initial Defects and Corrosion-Induced Cracking of the Concrete

Abstract This paper studies the spatial distribution of the corrosion products in concrete based on a series of experimental investigations of a marine construction. The distributions of defects and corrosion products in the concrete cover were identified in a mesoscale based on the computed tomography test, and the fractal dimension of cracks was analyzed. Some cracks and defects were filled by corrosion products in various degrees. The results showed that the defects were significantly influenced by the shape and relative location of the deformed steel reinforcement, which would then lead to the variation of the corrosion layer. The migration of corrosion products was particularly affected by the location and geometry of the defects, which could provide a suitable channel for the migration of corrosion products. The research can be helpful for the prediction of concrete cracking performance induced by the chloride-induced corrosion of the steel reinforcement.

Machine learning-based prediction for residual bearing capacity and failure modes of rectangular corroded RC columns

Chloride-induced corrosion of steel reinforcement is likely to change the failure modes of reinforced concrete (RC) columns in marine environments under the combined action of vertical and seismic load. This study was aimed to predict the residual horizontal bearing capacity and failure modes of corroded RC columns based on machine learning (ML) methods. First, a database (163 flexural failure, 26 flexural-shear failure, and 35 shear failure) of rectangular corroded RC columns was established according to predefined selection criteria. Then, 6 efficient ML algorithms, including support vector machine, artificial neural network, k-nearest neighbors, convolutional neural network, random forest, and categorical boosting, were employed to establish predictive models for evaluating the residual bearing capacity and failure modes of corroded RC columns. Based on the SHapley Additive exPlanations (SHAP) method, the importance of input characteristic parameters was ranked and how the input parameters make decisions to obtain the final output results explained. Finally, influences of stirrup corrosion level (ηt), shear-span ratio (λ), and axial load ratio (n) were investigated regarding the residual bearing capacity and failure mode evolution of corroded RC columns. The results show that the proposed ML models can effectively predict the residual bearing capacity and failure modes of corroded RC columns and exhibit great potential for describing the relationship between input variables and output results.

Experimental study on cyclic flexural behaviour of GFRP-reinforced seawater sea-sand concrete slabs with synthetic fibres

Seawater and sea-sand (SWSS) concrete is a new type of concrete with many economic and environmental benefits. However, chloride-induced corrosion of steel reinforcement is a major problem associated with this type of concrete. Due to its excellent resistance in chloride environments glass fibre reinforced polymer (GFRP) reinforcement could be utilized in SWSS concrete as an alternative to steel Adding fibres can also improve the concrete properties reinforced with GFRP bars. Fibres can affect the post-crack response and failure mode of GFRP reinforced concrete and also improve the bond between rebar and concrete. This study focused on the flexural behaviour of GFRP reinforced SWSS concrete slabs with or without fibre incorporation which has not yet been fully addressed in the literature. Polypropylene (PP) and polyvinyl alcohol (PVA) fibres were used for the concrete reinforcement. Under-reinforced (ρ < ρb) and over-reinforced (ρ > ρb) GFRP reinforced concrete (RC) slabs were prepared and subjected to four-point cyclic bending loads. The results show that GFRP bar is a promising alternative to steel for SWSS concrete reinforcement. The GFRP RC slabs with plain SWSS concrete had a cracking moment which was 13% lower than the values predicted by the ACI 440.1R-15 provisions. However, adding fibres, particularly PP fibres, could successfully compensate for this reduction. Variation in GFRP reinforcement ratio had almost no effect on cracking moment. With the addition of fibres, the cracking moment and ultimate strength of the slabs were both improved. Crack width and crack spacing were reduced in fibre-reinforced SWSS concrete slabs compared with the plain concrete counterparts. Fibres reduced the residual deflection of the slabs at the end of each cycle. Comparing experimental deflection results with the values predicted by different models revealed that there is no available model could satisfactorily predict deflection for all the GFRP reinforced SWSS slabs.

Floating breakwater pontoon pilot cast with carbon textile reinforcement-based ultra high durability concrete: Materials development and testing, and implementation in the North Atlantic (Irelands west coast)

A floating unit with three pontoons made of epoxy-coated carbon textile reinforced, ultra-high durability concrete (ECF UHDC), mineral impregnated carbon fibre-reinforced UHDC (MCF UHDC) and, as references, steel-reinforced concretes has been designed and installed in the Northern Atlantic. While marine structures with steel reinforcement require large cover depths, which cause problems in size, cost, environmental friendliness and short service life, carbon textile reinforced concrete (TRC) cannot suffer from chloride-induced corrosion of a metal reinforcement. In the EU H2020 project “ReSHEALience” (rethinking coastal defence and green-energy service infrastructures through enhanced-durability highperformance cement-based materials), TRCs have been modified with functional admixtures from consortium partners. A mineral self-healing promoter and alumina nano-fibers have, among others, been implemented to boost high-performance concretes towards UHDCs. Resulting composite variants have been applied in a full-scale floating unit that has been launched in the harbor of Galway at the Irish West Coast in June 2020. Such a floating body is a representation of breakwaters installed to reduce wave impacts to the coast. Besides, TRC-based UHDC can be applied as strengthening and repair layer on concrete structures to enhance their service life in general.

Impact of cracks on distribution of chloride-induced reinforcement corrosion

Surface crack width is regulated in codes to limit corrosion of reinforcement bars in concrete. However, the influence of surface crack width on corrosion damages is not directly inferable from previous research.In this work, data on corroded cracked concrete specimens in chloride environments was compiled. Detailed information was included, such as crack and pit locations, local corrosion pattern, etc. Five hypotheses on the influence of transversal cracks on corrosion damage were formulated, and statistical methods were used to test them on the dataset.Transversal cracks were good indicators of the position of corrosion pits. The corrosion rate of the pit increased in proximity of a crack. With time, pits grew in depth at a slower rate but increased in number. No clear correlation between surface crack width and corrosion damage was found. Results point out discrepancies in the collected data, arguing for the need of well-defined procedures for assessing crack and corrosion damage.Further, the statistical treatment allowed for identification of bias in existing data, which was used as a research planning tool to provide guidance on the design of additional experiments. Thus, recommendations for future experimental work required to reduce the bias are given.

Advanced modelling of concrete structures for improved sustainability

The safe and long-term serviceability of concrete structures is one of the methods how to improve the sustainability of the concrete industry. This study presents a pilot application of an~integrated system for online monitoring and service life prediction of concrete bridges. The system consists of strain gauges measuring the structural response coupled with a laser rangefinder for detection of the bridge-crossing traffic. The measured data were used for the development of a computational model of the bridge. Next, the deterioration models were applied to the model to assess the long-term mechanical behaviour. In this study, we considered chloride-induced reinforcement corrosion. The numerical data are given for 100-years-long service life prediction.

Dynamic Bayesian network for durability of reinforced concrete structures in long-term environmental exposures

Reinforced concrete (RC) structures under the marine environment may be subjected to chloride-induced corrosion of reinforcement, which significantly impacts the structural serviceability and reliability and further affects the sustainability and development of society. However, most of the existing durability assessment methods for RC structures only address their static and deterministic durability prediction and assessment at the design stage given the constant environment, ignoring the influences of stochastic environmental effects, uncertainties in structural properties, and inspection results. To this end, this paper proposes a dynamic Bayesian network (DBN) based durability assessment framework combined with a deterioration model that considers random changes in environmental parameters, convective chloride ion transport, and corrosion-induced cracking of concrete. In this framework, two-dimensional chloride transport and its influences on the durability deterioration assessment are concerned and achieved using the finite difference method. Besides, to reduce the deviations in probabilistic evaluation, the good-lattice-point-set-partially stratified-sampling (GLP-PSS) method is employed to establish a DBN framework. The proposed DBN framework is used for sensitivity analysis through a real-world example to examine the effects of the environmental model, chloride transport mode, and inspection results of concrete crack on durability assessment.

The Role of Cracks in Chloride-Induced Corrosion of Carbon Steel in Concrete—Review

The majority of works in the field of chloride-indued corrosion of steel in concrete are focused on the cracks formed by the corrosion products. However, the number of studies on the influence of cracks (pre-cracked concrete) on corrosion is limited. Cracks create preferential/free paths for the penetration of chlorides, water, and oxygen into concrete; thus, the presence of cracks in concrete can intensify chloride-induced corrosion of steel reinforcement. This paper presents a review of the effects of cracking on the corrosion of steel in concrete. It was widely reported in the reviewed papers that cracks have a negative impact on concrete durability. They influence the chloride penetration and the chloride-induced corrosion of reinforcement in terms of the initiation and propagation stages. This influence is a complex function of many factors, including mix design, exposure conditions, crack frequency, crack orientation, crack width, and cover depth. Although there is a general agreement on the effects of cracks on the initiation of corrosion, the role of cracks and their widths on the propagation of corrosion in the long term is still under debate.

Predicting airborne chloride deposition in marine bridge structures using an artificial neural network model

Chloride-induced corrosion of reinforcement is the most frequent durability problem in marine reinforced concrete (RC) structures. In particular, marine structures are intrinsically exposed to chloride ingress due to airborne chloride deposition. However, monitoring airborne chloride deposition in marine structures is difficult, since conventional on-site measurement is time-consuming and very hazardous. This study presents a prediction model for airborne chloride deposition in coastal bridges based on an artificial neural network (ANN) using local marine meteorological data. Two data sets were prepared for training: chloride deposition data in the (1) presence and (2) absence of scattered deicing salts. The proposed ANN model successfully predicted airborne chloride deposition at three different sampling sites in a coastal bridge, despite the complex relationship between airborne chloride deposition and meteorological parameters. The sampling site, such as one near a vehicle highway, was a more important factor for chloride deposition than the bridge height.

Chloride-induced corrosion of steel reinforcement in mortars manufactured with alternative environmentally-friendly binders

There is increasing interest in exploring the durability of structures manufactured with cements that are more environmentally friendly than traditional Portland. Accordingly, protection against chloride-induced corrosion of carbon steel reinforcement in mortars manufactured with environmentally friendly hybrid cements and alkali-activated materials (AAM) needs to be analyzed in-depth. Hybrid cements are innovative alternative binders with reduced amount of clinker in their formulation (20–30%). Their precursors are aluminosilicate wastes and they are very feasible in-construction implantation because they are not activated neither with liquid solutions of strong alkalinity nor external heating. In this research, AAM mortars were manufactured using slag from industrial by-products activated with sodium silicate. Hybrid mortars were manufactured either from fly ash or from slag, and activated with Na2SO4. Portland cement (CEM IV) mortars were also included in this study as reference. Chlorides were made to penetrate into the four different mortars under study by diffusion. The porosity and chloride penetration were evaluated and related to the different materials. The electrochemical behavior of the steel reinforced mortar specimens was monitored by open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) measurements. The corrosion rate values obtained for steel embedded in AAM were similar to conventional CEM IV mortars, and the morphology of the attack is less localized.

Blast fragility analysis of RC columns considering chloride-induced corrosion of steel reinforcement

Chloride-induced corrosion of steel reinforcement is one of the key factors that influences the life cycle performance and load-carrying capacities of concrete structures. For concrete structures that might be subjected to explosion hazards during the service life, the fragility analysis with the consideration of chloride-induced rebar corrosion provides quantitative information on lifecycle performance of structures against blast loading. This study performs the fragility analysis of reinforced concrete (RC) columns considering chloride-induced corrosion of steel reinforcement subjected to blast loading. General corrosion and pitting corrosion are considered in this study. Monte Carlo simulations are carried out in the study to calculate the failure probabilities. The mean and standard deviation of the degraded diameter and yield stress of the reinforcement up to 90 years after the corrosion initiation is established, which is incorporated in the existing empirical formulae for constructing the P-I curves of RC columns to predict its deteriorated blast loading-resistance capacity with time. In the analysis the blasting scaled distance is used as the demand intensity measure, random fluctuations of the peak reflected pressure, positive blast loading duration, concrete compressive strength, thickness of the concrete cover, diameter and yield stress of steel reinforcement are considered in the simulations. The blast fragility curves of typical RC columns are generated with respect to different damage levels corresponding to the number of years after corrosion initiation. It is found that the damage probability of RC columns increases significantly with steel reinforcement corrosion deterioration. Parametric analyses have shown that the column size is a more dominant factor, in comparison with the reinforcement ratio, of the RC columns on the blast resistance capacity corresponding to the minor damage levels. It is also found that the longitudinal reinforcement ratio is a less dominant factor than transverse reinforcement ratio on blast fragility curves of RC columns to resist blast loading. The blast resistance capacity of RC columns deteriorates significantly with corrosion damage.

A study on effectiveness of inorganic and organic corrosion inhibitors on rebar corrosion in concrete: A review

Reinforced concrete is the most extensively used building material in the construction industry. Generally, well-made concrete provides good physical and chemical protection to the embedded steel bar against an aggressive environment. The highly alkaline concrete pore solution protects the steel reinforcement from aggressive ions by forming a passive oxide layer over the steel surface. However, the passive film can be destroyed, and corrosion of steel reinforcement can be initiated either due to carbonation or due to the presence of a sufficient amount of chloride ions at the rebar level. Chloride induced corrosion of steel reinforcement affects the durability and decreases the service life of reinforced concrete structures exposed to aggressive environments, which results in huge repair and maintenance costs. By keeping in view, the substantial economic loss incurred due to corrosion of steel reinforcement in reinforced concrete structures, it is necessary to adopt adequate measures to minimize the corrosion of steel reinforcement in concrete. The most common corrosion prevention technique is the use of corrosion inhibitors in concrete. Several research works have been reported in the literature to evaluate the efficiency of corrosion inhibitors against chloride-induced corrosion of steel reinforcement in concrete. Corrosion inhibitors are typically introduced either as an admixture during the preparation of fresh concrete mixes or as a surface application on the hardened concrete to prevent the onset of corrosion of steel reinforcement or extend the corrosion initiation time in reinforced concrete structures. This review article summarizes the reported research works on inhibiting the behaviour of organic and inorganic corrosion inhibitors against chloride-induced corrosion of steel reinforcement in simulated concrete pore solution such as saturated calcium hydroxide solution containing varying concentrations of chloride ions as well as in cementitious composites. Further, the reported research works on the effect of corrosion inhibitors on the mechanical properties of cementitious composites are also are reviewed and discussed.

Impressed current cathodic protection of reinforced concrete in ATEX-zones – Case study: concrete slab in an industrial building

Electrochemical repair by means of impressed current cathodic protection (ICCP) was adopted as a repair strategy for a reinforced concrete slab, severely damaged by chloride induced reinforcement corrosion. Since the slab is located within an ATEX-zone (i.e. a zone with a potentially explosive atmosphere), strict safety regulations regarding the maximum current output through the cables had to be taken into account in the design of the ICCP system. Therefore, the anode in the zones of the CP system was subdivided into small fields (subzones), each individually connected to the power supply and provided with an electrical fuse in the circuit in order to avoid exceedance of the maximum allowed current. Performance assessment of the ICCP system, based on 24-hour depolarization measurements at regular time intervals, showed that complete protection of the steel reinforcement was obtained, according to the 100 mV depolarization criterium in the European standard EN ISO 12696, while the current output was kept well below safety limits. During a monitoring period of about one year, a decreasing required current density with time was observed, which was found to be 4 to 5 times lower than the adopted design value of 20 mA/m² at the start-up of the system and up to 10 times lower after 11 months of continuous application.

A Statistical Study of the Impact of Cracks on Chloride-Induced Reinforcement Corrosion

A Statistical Study of the Impact of Cracks on Chloride-Induced Reinforcement Corrosion

Modelling the impact of climat change on a novel Irish Concrete Bridge

This paper assesses the impact of climate change on the novel repair of Ferrycarrig Bridge, a reinforced concrete (RC) marine bridge on Ireland’s south-east coast. Five unique repair solutions were applied to the seven crosshead beams on Ferrycarrig Bridge during works in 2007. The two solutions under examination herein involved replacement of the concrete around the sides of the crosshead beams with either 100% Ordinary Portland Cement (OPC) concrete or concrete in which 60% of the cement was made up of Ground Granulated Blast Furnace Slag (GGBS) and 40% OPC. Changes to environmental policy mean that the use of GGBS within RC structures is becoming increasingly popular. Thus, understanding its performance over time is imperative. Chloride ingress and concrete crack modelling are completed herein to compare how climate change will affect the service life of the crosshead beams in which the OPC and OPC+GGBS concrete solutions are applied. The results stemming from this modelling are used to quantify the impact of reinforcement corrosion and concrete deterioration on the crosshead beams’ structural capacity. The findings indicate that without consideration of climate change, the OPC+GGBS concrete solution utilised in Ferrycarrig Bridge is 4.75 times more resistant to severe cracking caused by chloride-induced reinforcement corrosion than the OPC concrete solution. However, the durability of the OPC+GGBS concrete is more adversely affected by climate change with a lifetime reduction of 15.8% for the worst climate scenario as compared with a reduction of just 2.7% for the OPC concrete, reducing relative merit from 4.75 to 4.11.