Corrosion In Concrete Structures Research Articles

Transfer learning enables prediction of steel corrosion in concrete under natural environments

Existing machine learning (ML) models for corrosion rate prediction of steel in cementitious materials are typically established based on laboratory datasets obtained under controlled material and environmental conditions, which questions their applicability to more realistic and complex scenarios. Transfer learning (TL), as a branch of ML, can extract knowledge from a source domain, which can be utilized to improve prediction accuracy on a target domain. In this work, a TL paradigm, grounded on an advanced ML model built for steel corrosion in mortars, is proposed to elevate the efficacy of existing ML models in forecasting corrosion rate of steel in concrete under natural environments. The results underscore the prominence of certain features, specifically electrical resistivity, chloride-to-hydroxide concentration ratio ([Cl−]/[OH−]), cement proportion, corrosion potential, porosity, and water content. In addition, the interplay of diverse quantities of features and feature amalgamations exercises a substantial influence on the performance of ML models. It is found that TL strategy enhances the ML model's predictability for corrosion rate in concrete under natural environments. The knowledge pertaining to steel corrosion under controlled laboratory conditions can be transferred to enhance the model's ability to predict steel corrosion in concrete under natural conditions. These results underscore TL's potential in enabling reliable corrosion rate predictions in existing in-service concrete structures, especially with limited data and deficient information for steel corrosion in concrete structures.

Durability of marine concrete with nanoparticles under coupled action of fatigue load, dry–wet cycles and Cl− corrosion

The combination of multiple factors in marine environments can accelerate the concrete corrosion. In this work, bending fatigue load, dry–wet cycles and Cl− erosion were experimentally combined to evaluate the endurance of marine concrete incorporating nanoparticles (nano-silica (NS) and nano-titania (NT)). Dry–wet cycles of the nano-concretes were simulated in seawater (5% sodium chloride solution) and bending fatigue loads at stress levels of 0.5, 0.6, 0.7 and 0.8 were applied. The results indicated that the nanoparticles enhanced the resistance to Cl− erosion during dry–wet cycles and bending fatigue load by making the concrete more durable under coupled bending fatigue load, dry–wet cycles and Cl− erosion. The improvements were the most obvious for a NT content of 1% and a NS content of 2%, and the improvement was better with 1% NT than with 2% NS content is 2%. The free Cl− content in the concrete tension zone was larger than in the compressive zone. X-ray diffraction was used to assess the physical phases of the concretes before and after the experiments and to analyse the reasons for the increased concrete durability. The nanoparticles increases the content of hydrated calcium silicate in concrete, changed the orientation of calcium hydroxide and improved the concrete durability.

Biomimetic-induced hydroxyapatite for rebar corrosion mitigation in self-healing concrete beam

The corrosion of embedded rebar in self-healing concrete is seldom reported on and deserves more intensive attention. This study focuses on utilizing biomimetic-induced hydroxyapatite as a means of achieving autonomous self-healing to target issues associated with rebar corrosion in concrete structures. A comprehensive evaluation of the synthesized supramolecular hydrogel as self-healing agent carrier, the simulated self-healing products, and the reinforcement corrosion behaviour in the upscaled self-healing concrete beams was conducted. Results show that the synthesized 2,6-bis [N-(carboxyethyl carbonyl)amino] pyridine (DAP) hydrogel qualifies as a healing agent carrier with high loading capacity and intelligent response after cracking. The feasibility of hydroxyapatite formation via a combination of phosphate ions released by the supramolecular hydrogel and the available calcium ions leached by the cement matrix has been substantiated. The addition of phosphate as the healing agent is effective in mitigating the corrosion of rebar in the designed self-healing concrete beam. It can be explained by the synergistic effect of surface adsorption of chloride ions by the formed hydroxyapatite and the corrosion inhibitor role of the released phosphate.

Avaliação probabilística de estruturas de concreto sob corrosão – revisão sistemática da literatura

Abstract The evaluation of service conditions of concrete structures has still been carried out through implicit knowledge based on the expertise and knowledge of inspectors, who classify structures based on subjective criteria. The main degradation mechanism of reinforced and prestressed concrete structures is the corrosion of steel reinforcements, with expressive maintenance and repair costs. The phenomenon of corrosion in concrete structures has a complex behavior and presents several uncertainties, and deterministic analyzes can produce very conservative responses, which can unnecessarily increase maintenance costs, thus justifying probabilistic approaches. This article then presents a systematic literature review of articles that address the evaluation of concrete structures under reinforcement corrosion using a probabilistic approach. In this regard, 94 journal articles obtained through an appropriate review protocol were reviewed. Thus, the summary of the main proposed methodologies was carried out, as well as the identification of research gaps on the subject.

Modeling of chloride-induced corrosion in concrete bridge using the simplified and full probabilistic methods

Concrete and reinforced concrete structures are subjected to chloride corrosion, which can shorten their service life and safety of use. Reliability and safety prediction of concrete structures is a crucial task for optimizing their life cycle design and maintenance and for minimizing their life cycle costs. In the paper a probabilistic analysis of concrete durability in structural members is presented. Two methods: simplified-probabilistic and full-probabilistic have been applied for modelling chloride-induced corrosion in concrete structures. The uncertainty of the key parameters including surface chloride concentration, chloride threshold, cover depth and diffusion coefficient, which govern the chloride ingress into concrete and corrosion of reinforcing steel have been analyzed. A case study of a reinforced concrete bridge has been used to illustrate the capability and efficiency of these probabilistic methods in modeling the uncertainty and predicting the time-dependent probability of corrosion. FREeT-D and ProCAAT software have been used for the analysis.

Pure shear model for crack width analysis of reinforced concrete members

Reinforcement corrosion in concrete structures with excessive crack width poses a high risk of reducing the structure's service life. The crack width behavior is one of the most complex aspects of the mechanics of reinforced concrete (RC). With most of the models used in practice being semi–empirical or empirical, very few analytical approaches have been proposed. However, the analytical models lack either accuracy or simplicity, or both. This paper presents a new analytical model, termed the Pure Shear Model, that predicts mean crack width by a simple formula. It is based on the partial interaction tension stiffening model considering a short RC tie subjected to short–term loading. The model assumes elastic material properties and neglects shrinkage, internal cracking, and slip at the interface. It presumes that the only deformations that occur in concrete are the shear strains due to shear lag that are taken constant across the cover thickness. Deplanation of concrete section due to shear lag results in crack width linearly increasing from zero at the bar to its maximum value on the surface of the RC member. Despite the simplicity of the proposed model, its accuracy in predicting mean crack width was shown to be comparable to that of the design code methods.

Bridging the Gap: Assessing Material Performance of Laboratory Specimens and Concrete Structures.

Chloride ingress and carbonation pose a significant risk of steel rebar corrosion in concrete structures. Various models exist to simulate the initiation phase of rebar corrosion, addressing both carbonation and chloride ingress mechanisms separately. These models also consider the environmental loads and material resistances, typically determined through laboratory testing based on specific standards. However, recent findings show significant differences between material resistances obtained from standardized laboratory specimens and those extracted from real structures, with the latter exhibiting inferior performance on average. To address this issue, a comparative study was conducted between laboratory specimens and on-site test walls or slabs, all cast using the same concrete batch. This study encompassed five construction sites featuring different concrete compositions. While laboratory specimens adhered to European curing standards, the walls were subjected to formwork curing for a predetermined period (typically 7 days) to simulate practical conditions. In some instances, a portion of the test walls/slabs received only one day of surface curing to emulate inadequate curing conditions. Subsequent testing of compressive strength and resistance to chloride ingress revealed that field specimens exhibited lower material resistance compared to their laboratory counterparts. This trend was also observed in the modulus of elasticity and carbonation rate. Notably, shorter curing periods further compromised performance, particularly resistance to chloride ingress and carbonation. These findings highlight the importance of establishing acceptance criteria not only for concrete delivered to construction sites but also for ensuring the quality of the actual structure.

Experimental Investigation on Carbonation due to Climate Change Impacts

<p>Various investigations have been carried out to evaluate the infrastructure’s augmented vulnerability owing to concrete carbonation persuaded by the changes in the environment during recent years. Due to global warming and its effect, carbon dioxide emission levels in the atmosphere get increased and this would further increase the probability of carbonation-induced corrosion in concrete structures. In this present study, an empirical model is used to identify the diffusion coefficient of carbon dioxide (CO2) in concrete. Water cement (w/c) ratio of 0.45, 0.5, and 0.55 has been considered with emission scenarios of Representative Concentration Pathway (RCP) 8.5 and 4.5 respectively. The research findings through empirical modeling proved that the depth of carbonation has a direct relationship with water cement ratio and it is also predicted that by the year 2100, considering 2000 as the base year, the carbonation depth may raise up to 78% for reinforced concrete structures subject to various climatic conditions such as temperature, humidity, etc.</p>

The Influence of Assembly Unit of Fibers on the Mechanical and Long-Term Properties of Reactive Powder Concrete

The corrosion of concrete structures by chloride salt is very significant in coastal environments. In order to improve the durability of marine concrete structures, cement-based materials with high durability need to be developed. In this investigation, the influence of NaCl freeze–thaw cycles (FT-C) and NaCl dry-wet alternations (DW-A) on the flexural and compressive strengths of reactive powder concrete (RPC) with an assembly unit of basalt fibers and steel fibers is studied. Additionally, the mass loss rate, the relative dynamic modulus of elasticity (RDEM), the chloride ion migration coefficient (CMC) and the impact toughness are measured after the NaCl FT-C and DW-A action. Our findings show that the RDEM, mass loss, and mechanical strength loss of RPC are increased by the ascending NaCl FT-C and DW-A. Meanwhile, the RDEM and the impact toughness are decreased by the NaCl FT-C and DW-A. The RPC with 0.5% basalt fibers and 1.5% steel fibers by volume of RPC shows the optimum mechanical performance and resistance to NaCl FT-C and DW-A. However, RPC with 3% steel fibers shows the worst resistance to NaCl erosion. The maximum mass loss rates, RDEM, flexural strength loss rate, compressive strength loss rate, CMC and impact toughness of all specimens after 300 NaCl FT-C and 30 NaCl DW-A are 4.5%, 91.7%, 28.1%, 29.3%, 3.2 × 10−12 (m2/s) and 2471 J. Meanwhile, the corresponding minimum values are 1.62%, 83.2%, 20.4%, 15.7%, 1.1 × 10−12 (m2/s) and 625 J. The researching findings will provide an optimum mix ratio of RPC with an assembly unit of basalt fibers and steel fibers, which can be applied in the marine engineering environment.

Grading assessment of steel bar corrosion in concrete structures based on naive Bayesian model and spontaneous magnetic flux leakage effect

In order to explore an accurate method to evaluate the corrosion of reinforced concrete structures, the spontaneous magnetic flux leakage (SMFL) signal distribution on the surface of reinforced concrete specimens under different corrosion degrees was scanned based on SMFL technology. The influence of steel bar length, steel bar diameter, and other parameters on the distribution of SMFL signal was studied. The correlation between steel bar corrosion and the characteristic magnetic index of concrete structure was explored. Based on the naive Bayesian model, the classification evaluation of the steel bar corrosion degree of concrete structure was carried out. The results show that the variation of SMFL signal is affected by the corrosion degree α. When the lift-off height and the thickness of concrete protective layer remain unchanged, the slope between the peak and trough of Bz (magnetic induction intensity along z direction) curve increases with the increase of α, and the trough of Bx (magnetic induction intensity along x direction) curve decreases with the increase of the corrosion degree α. The peak and trough of magnetic signal curve can be used as the basis for determining the corrosion position. There is a strong correlation between the magnetic characteristic index β, γ, and the steel corrosion degree α obtained by SMFL. Through the characterization relationship between α, β, and γ, the corresponding models of single and comprehensive index β and γ were established. The results showed that the accuracy of β and γ integrated discriminant Naive Bayesian model-III reached 90.7%, which proved that the evaluation method has high reliability. This study explores the application of SMFL in corrosion detection of concrete structures.

New semiempirical temporal model to predict chloride profiles considering convection and diffusion zones

Chloride ions are primarily responsible for reinforcement corrosion in concrete structures in the marine environment. Thereby, analyses regarding chloride penetration into concrete are fundamental for service life estimates, in which the chloride concentration profiles provide quantitative information for prediction models. However, the conventional modeling method based on the solution of Fick's second law of diffusion usually only fits the diffusion profile zone and does not represent the convection zone. Therefore, this article shows a new model for complete chloride profile modeling. The semiempirical double exponential model was developed by approximating Fick's second law using the finite difference method and validated with chloride profiles from structures under natural degradation for more than 40 years. The double exponential model proposed can fit in the two profile zones, showing higher efficiency than Fick's model, and stands out for expressing the variation in chloride peak depth over time.

The Prediction of Steel Bar Corrosion Based on BP Neural Networks or Multivariable Gray Models.

The corrosion of steel bars in concrete has a significant impact on the durability of constructed structures. Based on the gray relational analysis (GRA) of the accelerated corrosion data and practical engineering data using MATLAB, a back propagation neural network (BPNN) model, a multivariable gray prediction model (GM (1, N)), and an optimization multivariable gray prediction model (OGM (1, N)) of steel corrosion were established by using a sequence of the key affecting factors. By comparing the prediction results of the three models, it is found that the GM (1, N) model has larger fitting and prediction errors for steel corrosion, while the OGM (1, N) model has smaller prediction errors in the accelerated corrosion data; the BPNN model offers more accurate predictions of the practical engineering data. The results show that the BPNN and OGM (1, N) models are all suitable for the prediction of steel bar corrosion in concrete structures.

Acoustic emission testing for multi-scale assessment of reinforcement corrosion in concrete structures

Degradation of existing structures poses a serious threat to our built environment. The aim of this paper is to investigate the use of acoustic emission monitoring in degradation assessment of existing structures, focusing specifically on corrosion damage detection in reinforced concrete structures. Reinforcement corrosion is seen as one of the most significant and costly degradation mechanisms that impact the durability and structural safety of our built infrastructure and Modern heritage buildings. The paper presents a multi-scale experimental approach, from material to structure, focusing on two challenges: (i) monitoring the evolution of the corrosion process itself and the consequential concrete cracking during accelerated corrosion, and (ii) identifying the different AE sources in this complex process. The application of AE testing for rebar corrosion monitoring is investigated on various sample types and scales under accelerated conditions in a lab environment, and from on-site monitoring of a concrete girder bridge. Results show that the developed test setups, data filtering and processing procedures substantially improve AE-based corrosion damage monitoring, and provide a valuable contribution towards on-site application.

Influence of various parameters on the current distribution and protection degree of impressed current cathodic protection for reinforced concrete with TiMMO mesh anodes

Impressed current cathodic protection (ICCP) is an effective technique to control reinforcement corrosion in concrete structures. The efficiency and design of an ICCP system with titanium mixed metal oxide (TiMMO) anodes in a mortar overlay is strongly influenced by the current distribution to the different reinforcement layers of a reinforced concrete element. An in-depth experimental study is performed to investigate the effect of various parameters on the current distribution and degree of corrosion protection: (i) chloride content, (ii) cement type, and (iii) reinforcement configuration. 24-hour depolarization measurements (EN ISO 12696:2022) indicate that an increase in chloride concentration in the concrete, related to an increase in the rate of reinforcement corrosion, leads to a general decrease in the degree of protection. The use of a CEM III/A cement leads to a large increase in concrete electrical resistivity compared to concrete with an ordinary Portland cement (CEM I). This causes a lower total current output to the reinforcement and a less uniform distribution of current. Finally, a lower steel reinforcement density resulted in a larger current density, as the total current is distributed over a smaller steel surface area, causing higher depolarization values.

Effects of treated corrosion reinforcement on structural behavior of concrete beams

Structural degradation phenomena like reinforcement corrosion in concrete structures imply a consequent reduction in time of the safety level. Corrosion causes a reduction of the sectional area, ductility and strength of rebars, bond strength between steel and concrete. The subsequent redistribution of internal stresses induces a reduction in ductility at ultimate limit state and a variation of the deformational behavior in serviceability conditions. In this paper, an experimental investigation was carried out to study the effect of treated corrosion reinforcement on structural behavior of concrete beams. In this investigation, phosphoric acid and vinegar solution are used to treat the corroded steel bars and compared the bending strength of concrete beams with treated and untreated corrosion reinforcement. A finite element computer software (ANSYS) has been used to compare the experimental results. From the experimental and analytical results, it was observed that performance of concrete beams with treated corrosion reinforcement is better than the concrete beams with corrosion reinforcement,

A functional and robust super‐hydrophobic PCC coating based on the induced assembly of modified zirconium phosphate

AbstractImproving the permeability of concrete is one of the important measures to extend the service life of concrete. In addition, for marine engineering, sewerage projects, and so on, mechanical stability and microbial induced corrosion of concrete structures cannot be ignored. We demonstrated a method to prepare high‐performance super‐hydrophobic (SHP) coating using functional zirconium phosphate (ZrP) and polydopamine (PDA) as the primary materials. The micro‐nano rough structures were constructed on the concrete surface by alternating organic–inorganic assembly guided by each other. The coatings' apparent morphology, composition, and structure were analyzed using various surface analysis techniques. Based on the construction of micro‐nano rough structures by the induced assembly of functional ZrP, the silane treatment significantly improved the water contact angle of the coating (WCA = 154° ± 3°), and the coating exhibited relatively high wear resistance, reaching 135° WCA even after 30 friction cycles. The water absorption of the specimens treated with the SHP composite coating was reduced by 79% to treated with silane. Meanwhile, the SHP composite coating showed excellent antimicrobial and anti‐ice properties, due to the role of the functional ZrP and alternating organic–inorganic assembly. It was expected that the composite coating might potentially promote and accelerate applied superhydrophobic anticorrosive coating development for marine concrete durability.

The equivalent quantization method of corrosion damage of reinforcement cage for concrete beam and its durability in island and reef environment

• The equivalent quantization method of corrosion damage of concrete beam was proposed and verified. • Effects of four factors with twelve levels on durability of concrete beam were studied. • Three types of self-produced protective materials were tested. • The relation between the linear polarization resistance and electrochemical impedance spectroscopy methods was established. The electrochemical measurement technique was used to conduct a non-destructive test the corrosion degree of reinforcement cage for concrete beam in tidal environment of island and reef region in real-time. Apart from this, the corrosion resistance of concrete beam with different concrete strength grades, steel bar, darex and migrating corrosion inhibitors, including three types of self-produced protective materials, was studied. Furthermore, based on electrochemical parameters, the relation of electrochemical measurement techniques was established. The results showed that the proposed equivalent quantization method of corrosion damage could be available for the reinforcement cage in concrete beam. In addition, the durability of concrete beam in tidal environment of island and reef region can be effectively improved by improving the concrete strength grade and the corrosion resistance of steel bar and using darex and migrating corrosion inhibitors. The polarization resistance obtained by the linear polarization resistance method and charge transfer resistance obtained by the electrochemical impedance spectroscopy method were linear. This study provides a key technology for actual reinforcement corrosion in concrete structure and some protective measures.

Steel corrosion damage monitoring in reinforced concrete structures with the acoustic emission technique: A review

• An in‐depth literature review and discussion on AE‐based corrosion monitoring in RC is presented. • Consistency of parameter‐ and signal‐based AE methods for corrosion monitoring is analyzed. • AE‐based condition assessment of corroded RC elements during load testing is discussed. • An overview on availability of AE data sets for corrosion tests in lab and in‐situ is presented. • Research challenges for in‐situ monitoring of corrosion damage in RC structures are discussed. Corrosion is a major issue in construction and infrastructure management, giving rise to high repair costs, safety concerns and structural failures. Especially reinforcement corrosion in concrete structures is a complex issue. As degradation starts internally, visual inspection lacks efficiency in early stages of the corrosion process. Acoustic Emission (AE) monitoring provides major advantages as this technique enables to detect internal damage in an early stage. However, the use of AE monitoring also comes with certain challenges. The aim of this paper is to review appropriate protocols for AE-based reinforced concrete (RC) corrosion monitoring based on an overview of reported lab experiments, highlighting challenges and pitfalls, and to provide a solid basis for extension of the research focus towards on-site AE-based corrosion monitoring in RC structures. Therefore, this paper firstly discusses AE monitoring during (accelerated) corrosion tests, including methods for data analysis and best-practice protocols. Secondly, application of the AE technique for condition assessment of corroded RC elements during load testing is discussed. Thirdly, an overview is presented of reported on-site AE monitoring studies on corroding RC structures. The paper concludes with a discussion and future research challenges, especially towards on-site monitoring of existing RC structures.

Axial behavior of circular seawater sea-sand coral concrete columns reinforced with BFRP bars and spirals

• Axial behavior of BFRP bars reinforced seawater sea-sand coral concrete columns was studied experimentally. • The load bearing capacity of B-SSCC columns declined as the spiral spacing narrowed paradoxically owing to the significant discontinuity of coral concrete internally. • Columns with dense stirrups showed more pronounced ductility in the post-peak stage compared with B-SSCC square columns. • An ultimate bearing capacity prediction model is established. For the sake of solving the problem of steel reinforcement corrosion in concrete structures and reducing the transportation cost of concrete raw materials at sea in the development of South China Sea Islands, a new type of coral reef sand concrete columns reinforced with basalt fiber reinforced polymer (BFRP) bars and spirals was proposed. In this study a total of 18 circular seawater sea-sand coral reef concrete columns reinforced with BFRP bars and spirals (B-SSCC) were tested under concentric axial loads. Parameters of nominal longitudinal bar diameters and spiral spacing were investigated to obtain variations on crack propagation, failure modes, load bearing capacity, strain and ductility properties. The results indicated that no obvious cracks were observed until the curves reached up to 0.95 P max approximately and the columns experienced more brittle and explosive failure modes with the increase of longitudinal bar diameter and spiral spacing. The load bearing capacity of B-SSCC columns increased with longitudinal reinforcement ratio, however, declined as the spiral spacing narrowed paradoxically. It was owing to the significant discontinuity of coral concrete internally. Compared with B-SSCC square columns, the circular columns with dense stirrups showed pronounced ductile behavior in the post-peak stage, remarked by improved average ductile coefficient β of 22.6%. Finally, a numerical prediction of load bearing capacity was suggested.

Oxygen Availability and Corrosion Propagation in RC Structures in the Marine Environment—Inferences from Field and Laboratory Studies

The splash and spray and tidal zones are generally assumed to be the most severe marine exposure environments with respect to steel reinforcement corrosion in concrete structures. However, it has been observed in several aged marine structures along the Southern African coastlines, that there is usually relatively insignificant reinforcement corrosion damage in the tidal zone, despite very high (above-threshold) chloride contents. To develop a full understanding of the severity of marine exposure conditions with regard to the actual deterioration, it is imperative that other factors that directly affect corrosion, such as oxygen availability at the steel surface (which is influenced by concrete quality, cover thickness and moisture condition), are carefully considered. The laboratory experimental work in the study presented in this paper comprised of different cover depths (10, 20 and 30 mm) and w/b ratios (0.5 and 0.8) and simulated marine tidal, splash and submerged environments. The results show that for any give exposure environment, the relative influence of each of the various factors considered should be considered in conjunction with the other factors; this finding can be generalized to include all relevant factors that can affect corrosion in a given exposure environment including ambient temperature. For example, a cover depth of 30 mm in the tidal zone with a simulated intertidal duration of 6 h effectively resulted in similar corrosion behavior to that in the submerged zone. The paper concludes that engineers should consider these factors when applying standard exposure classes in the design for durability of marine structures.