Carbonation-induced Corrosion Research Articles

Integrating machine learning and Monte Carlo Simulation for probabilistic assessment of durability in RC structures affected by carbonation-induced corrosion

Integrating machine learning and Monte Carlo Simulation for probabilistic assessment of durability in RC structures affected by carbonation-induced corrosion

Fundamentally understanding carbonation-induced corrosion of steel in environmentally friendly concretes

Reducing greenhouse gas emissions in concrete production is crucial to achieve sustainability goals. One of the primary solutions is employing environmentally friendly cements with lower clinker content, such as those containing supplementary cementitious materials. However, concretes produced with some of these cements are vulnerable to fast carbonation, which raises durability concerns regarding corrosion of the steel reinforcement. While traditional approaches focus on preventing concrete carbonation and corrosion initiation, evidence shows that corrosion rates of steel in carbonated concrete do not necessarily compromise durability. In this context, the fundamental understanding of the kinetics of carbonation-induced corrosion must be improved, considering the role of the concrete pore solution, pore structure, and moisture content, as discussed in this paper. Open questions and promising approaches to clarify them are also discussed. Based on this knowledge, corrosion propagation can be properly included in the service life design of reinforced concrete structures, reconciling the goals for both sustainable and durable structures.

Influence of Corrosion on Lifespan of Reinforced Concrete Structures: A Comprehensive Review

Carbonation-induced corrosion is a major concern for reinforced cement concrete (RCC) structures, impacting their long-term durability and structural integrity. This review synthesizes the findings on the deterioration mechanisms in concrete structures, focusing on carbonation, chloride-induced corrosion, and time-dependent deterioration. The analysis includes discussions on predictive likelihood methods for estimating bridge reliability, the impact of environmental factors on carbonation, and standardized testing methods for assessing concrete durability. The review highlights the importance of understanding material characteristics and environmental conditions in designing durable concrete structures, emphasizing the processes of carbonation, its impact on rebar corrosion, and strategies for mitigation. Sheltered concrete carbonation resistance in metropolitan tropical climates is 10-20% lower than open exposure. SCM concretes exhibit equivalent or greater long-term carbonation resistance to OPC concretes, as evidenced by the increase in carbonation depth ( Δ xd) at ages greater than 5 years. The paper concludes with recommendations for integrating advanced modeling techniques and empirical studies to develop robust maintenance strategies and improve concrete mix designs for enhanced durability.

Predicting the impact of water transport on carbonation-induced corrosion in variably saturated reinforced concrete

A modelling framework for predicting carbonation-induced corrosion in reinforced concrete is presented. The framework constituents include a new model for water transport in cracked concrete, a link between corrosion current density and water saturation, and a theory for characterising concrete carbonation. The theoretical framework is numerically implemented using the finite element method and model predictions are extensively benchmarked against experimental data. The results show that the model is capable of accurately predicting carbonation progress, as well as wetting and drying of cracked and uncracked concrete, revealing a very good agreement with independent experiments from a set of consistent parameters. In addition, insight is gained into the evolution of carbonation penetration and corrosion current density under periodic wetting and drying conditions. Among others, we find that cyclic wetting periods significantly speed up the carbonation progress and that the induced corrosion current density is very sensitive to concrete saturation.

Study on carbonation of low strength concrete made of brick aggregate

In urban and industrial settings, one of the most prevalent durability challenges faced by reinforced concrete (RC) structures is the corrosion of steel reinforcement due to carbonation. While numerous studies have explored the characteristics of stone aggregate concrete concerning carbonation-induced corrosion of reinforcement, there is limited research on concrete made with brick aggregates. As a result, an investigation into the impact of carbonation on pre-existing reinforced concrete structures utilizing brick aggregates has been undertaken, and its findings have been compared with existing research. Within this study, a total of 84 concrete core samples, with diameters measuring 67 mm and 50 mm, were extracted from selected structural components of four pre-existing reinforced concrete structures utilizing brick aggregates, which ranged in age from 17 to 73 years. The collection of core samples and their testing procedures adhered to the relevant ASTM methods. Furthermore, carbonation depths were assessed in accordance with BS standards using phenolphthalein solution. Additionally, 24 concrete dust samples were gathered from the same locations to establish correlations with the core sample results. The experimental outcomes revealed a direct relationship between carbonation depth and concrete age, indicating that carbonation depth increases with concrete age. This study also demonstrated that the rate of carbonation is influenced by the concrete's grade, with an inverse relationship between them. Therefore, it is crucial to consider carbonation in scenarios involving low-strength concrete, particularly those with compressive strengths below 25 MPa, when the concrete is exposed to harsh environmental conditions and inadequate concrete cover. Consequently, when constructing new structures, employing relatively high-strength concrete is advisable to ensure extended service life by mitigating the effects of carbonation.

Carbonation-Induced Corrosion on Concrete with Waste Brick Powder and Hydrated Lime Additive

Carbonation-Induced Corrosion on Concrete with Waste Brick Powder and Hydrated Lime Additive

Variation of Corrosion Rate, Vcorr, during the Carbonation-Induced Corrosion Propagation Period in Reinforced Concrete Elements.

The structural systems of residential buildings in many developed countries have widely utilized reinforced concrete as the most common solution in construction systems since the early 20th century. The durability of reinforced concrete columns and beams is compromised, in most cases, by pathologies caused by the corrosion of their reinforcements. This study analyses the corrosion processes induced by carbonation in 25 buildings with reinforced concrete structures. The models estimate the service life of reinforced concrete elements by differentiating between the initiation period and the propagation period of damage, considering two possible stages: the time of corrosion propagation until the cracking of the concrete cover, and the time of propagation until a loss of section is considered unacceptable for structural safety. However, the mathematical expressions that model the propagation periods consider the same corrosion rate in both cases. This research has found that the average corrosion rate in elements with an unacceptable loss of reinforcement section was in the order of 8 times higher than the corrosion rate in cracked columns and beams without a loss of reinforcement. This opens up a path to improve the definition of the different stages experienced by a reinforced concrete element suffering corrosion of its reinforcements due to carbonation, because once the concrete has cracked, the corrosion rate increases significantly.

Service Life Design of Concrete Structures Made of High-Volume Limestone Powder Concrete—Case of the Carbonation-Induced Corrosion

One of the paths to CO2 emissions reduction in the concrete industry is to use low-clinker cements, providing at the same time the performance of concrete that is adequate for application in concrete structures. This paper explores the impact of the clinker replacement with high amounts of limestone powder (21–70% in the powder phase) on concrete carbonation resistance. To quantify this impact, the empirical relationship between the carbonation resistance and the compressive strength of the high-volume limestone powder concrete (HVLPC) was established. For that purpose, the regression analysis was applied on the experimental results collected from the published research. The service life analysis based on the full probabilistic approach was performed using the fib Model Code 2010 prediction model and proposed empirical relationship. The first-order reliability method (FORM) was applied to solve the limit state function of reinforcement depassivation with a reliability index equal to 1.3. The obtained minimum concrete cover depths were 40–110% higher compared to those prescribed in the current European standard EN 1992-1-1:2004 for indicative strength classes. Based on the full probabilistic analysis, recommended cover depths are given for all carbonation exposure classes, commonly applied concrete strength classes, and service lives of 50 and 100 years.

Probabilistic approach to the sustainability assessment of reinforced concrete structures in conditions of climate change

The paper presents a probabilistic method based on two methodologies – Life Cycle Cost Analysis (LCCA) and Life Cycle Assessment (LCA), for evaluating the sustainability of reinforced concrete (RC) structures in terms of their costs and CO2 emissions. The method considers the whole life of a RC structure by taking into account CO2 initially embodied in its construction materials, the absorption of CO2 by concrete due to carbonation during the service life of the structure, potential damage to the structure due to carbonation-induced corrosion of reinforcing steel that may require repairs, and relevant costs. Since there are numerous uncertainties associated with the calculation of CO2 emissions and costs, a probabilistic approach is beneficial. The emphasis is made on RC structures made of the so-called “green concretes”, in which Portland cement is partially replaced with supplementary cementitious materials such as fly ash and ground granulated blast-furnace slag. The issue of a changing climate is also addressed. The method is illustrated by assessing the sustainability of a multi-story RC carpark made of different concrete types at three different locations (London, Paris and Marseille) for present and future climate conditions. This assessment's results show that using green concretes leads to a major reduction in CO2 emissions and a small decrease in the life-cycle cost of the carpark RC elements. The relative sustainability performance of green concretes slightly improves compared to Portland cement concrete for future climate conditions.

Dynamic behavior investigation of reinforced concrete bridge under multi-hazard effect of rockfall impact and material corrosion

Rockfall disasters pose a significant threat in mountainous areas, leading to severe damage and potential collapse of transportation infrastructure. On the other hand, the concrete and steel materials used in these structures deteriorate over time due to environmental corrosion. Therefore, this paper aims to comprehensively investigate the dynamic behavior of the bridge pier of a simply supported reinforced concrete (RC) bridge under the multi-hazard effect of rockfall impact and material corrosion. To achieve this, a comprehensive framework is proposed for analyzing the impact force and dynamic displacements of the bridge pier, which incorporates carbonation-induced corrosion models of concrete and steel, the bond-slip model, and the contact collision model for rockfall impact analysis. The study then explores the influences of various factors, including carbonation degree, rockfall weight, impact velocity, and impact angle, on the maximum impact force and dynamic displacements experienced by the bridge pier. Experimental data from a simply supported RC beam subjected to drop hammer impacts were employed to validate the correctness of the numerical modeling method. Subsequently, the numerical model of a two-span simply supported bridge was established to comprehensively investigate the dynamic behavior of the bridge pier under the combined effects of rockfall impact and material corrosion. The findings reveal that the impact force peak does not exhibit a clear relationship with the carbonation degree, but the displacement peak increases with the carbonation degree when the material corrodes over 60 years. Furthermore, the rockfall impact force peak and the displacement peak show a nonlinear increase in impact velocities, rockfall weight, and impact angle. The outcome of this study holds important implications for the design of resilient bridges and the development of effective maintenance strategies for a multitude of bridges exposed to rockfall hazards.

Influence of Climate Change on Probability of Carbonation-Induced Corrosion Initiation

The consequences of climate change on infrastructure, particularly reinforced concrete (RC) bridges, have rapidly increased in recent years. These consequences are primarily driven by the surge in CO2 emissions, which significantly impacts the carbonation depth of RC structures. This study aims to investigate the probability of carbonation-induced corrosion initiation (PCICI) in RC bridge elements. To achieve this, the investigation incorporates a range of concrete covers, varying from 30 to 50 mm, and considers different concrete mixes with cement contents of 400, 350, and 250 kg/m3. The investigation utilizes the Monte-Carlo simulation method, considering different representative concentration pathways (RCPs) to account for two emission scenarios: RCP2.6 (low emission scenario) and RCP8.5 (high emission scenario). By analyzing projected CO2 concentrations and maximum temperature, the study provides insights into the potential corrosion initiation risks in RC bridges. The findings indicated a significant 66.3% increase in PCICI for a cement content of 250 kg/m3, compared to 400 kg/m3, under the RCP8.5 scenario, specifically when using a concrete cover of 30 mm by 2100. The study also revealed that the PCICI approached an approximate value of zero when concrete covers were set at 45 and 50 mm regardless of the variations in cement contents and the duration considered, for both the RCP2.6 and RCP8.5 scenarios.

A hybrid model based on convolution neural network and long short-term memory for qualitative assessment of permeable and porous concrete

Estimating design factors like concrete strength and durability is complicated by the cement industry's practice of producing multiple grades of cement for different uses, necessitating substantial labor hours and monetary investment. The experimental findings of accelerated carbonation-induced corrosion and associated durability characteristics of concrete built with high-volume Class F Fly Ash (FA), including AC impendence, half-cell potential, water permeability, and volume of permeable voids. FA was added to ordinary portland cement at varied replacement amounts (0–70%) to create concrete specimens. The concrete specimen has been prepared by varying different proportions of water cement ratio (0.45, 0.40, and 0.35). To predict the compressive strength and carbonation level of concrete, this study presents a simulation environment based on Artificial Intelligence (AI) that makes use of input parameters such as water/cement ratio, fly-ash percentage, and time duration. Here, One-Dimensional Convolution Neural Network based Long Short-Term Memory (1D-CNN-LSTM) has been proposed for estimating the carbonation depth and compressive strength of concrete. The developed model will be compared with other state-of-the-art techniques, including DL and ML-based techniques. The obtained R2 values from the proposed 1D-CNN-LSTM regression network deliver accuracy of 80% for estimating carbonation depth and 96% for predicting compressive strength. The proposed methodology demonstrates the use of modern AI-based techniques in the actual design model and illustrates the development of DL methods such as LSTM and CNN.

Carbonation-Induced Corrosion of Reinforced Concrete Elements according to Their Positions in the Buildings

Most regulations on the manufacturing of concrete for reinforced concrete structures rest on durability models that consider the corrosion of reinforcements. Those models are based on factors such as humidity, frost, presence of chlorides, and internal characteristics of the concrete itself, like resistance, porosity, type of cement, water/cement ratio, etc. No regulations, however, adopt a purely constructive perspective when evaluating the risk of corrosion, i.e., the relative position of the reinforced concrete in buildings. The present work focuses on the relationship between the position of the damaged element and the building envelope. A total of 84 elements (columns and reinforced concrete beams) across twenty buildings were analysed in the provinces of Alicante and Murcia (Spain). The reinforcement concrete of these elements underwent carbonation-induced corrosion according to their positions in the buildings: (A) façade columns in contact with the ground; (B) interior columns in contact with the ground; (C) columns of walls in contact with the ground; (D) columns and external beams protected from rain; (E) columns and external beams exposed to rain; (F) columns and beams in air chambers under sanitary slabs; and (G), columns and interior beams. Of all types, elements (E) and (F) suffered carbonation-induced corrosion faster than the models used in the regulations, and type (G) underwent slower carbonation.

Developing the inhibition mechanism for amide-based amino acids in carbonated concrete environment and assessing the migration ability in concrete

The corrosion inhibition mechanism of amide-based amino acids, Asparagine (Asn) and Glutamine (Gln) for steel in concrete pore solution simulating carbonated environment was explored by the means of gravimetric, electrochemical and surface characterization techniques. Thereafter, percolation ability of Asn and Gln was assessed through OPC and PPC concretes by UV–visible spectroscopy technique for their application as migratory corrosion inhibitors in concrete. The results revealed that Asn as well as Gln can be efficiently used in carbonated corrosive environment for steel inhibition. The protection ability of Gln was however, higher than Asn. Gln exhibited 50% lower corrosion current density values than Asn. Also, the charge transfer resistance of Gln inhibited specimens was 3 times higher than Asn inhibited specimens. The layer developed on steel with Gln as corrosion inhibitor was thermodynamically more stable than Asn as equilibrium constant of adsorption (kads) was 2.11 times higher for Gln. Optical and SEM images revealed the formation of a thin layer in the case of Asn while a thick layer was seen to form on Gln inhibited specimens. Surface layer characterization by FTIR and XPS evinced the formation of Asn-Fecomplex and Gln-Fecomplex on steel surface. Both the compounds bound the Fe ions by chelation through O atom from amide and carboxylate functional groups. Higher efficiency of Gln was attributed to development of more adherent protective film due to its longer carbon chain length than Asn. Gln’s chelate ring experienced lower steric hindrance than Asn’s ring. Asn and Gln percolated through concrete and reached upto a depth of 25mm within 15 days of application. Conclusively, it can be said that Asn and Gln can be employed as corrosion inhibitors for concrete subjected to carbonation-induced corrosion.

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>

Application of Adaptive Neuro-Fuzzy Inference Systems with Principal Component Analysis Model for the Forecasting of Carbonation Depth of Reinforced Concrete Structures

The carbonation of reinforced concrete is one of the intrinsic factors that cause a significant decrease in service performance in concrete structures. To decrease the effect of carbonation-induced corrosion during the lifetime of the concrete structure, a prediction of carbonation depth should be made. The carbonation of concrete is affected by many factors, such as the compressive strength of the concrete, service life, carbonation time, carbon dioxide concentration, working stress, temperature, and humidity. On the basis of these seven parameters, combined with the predictive power of the adaptive network-based fuzzy inference system (ANFIS) and principal component analysis (PCA), which can reduce data dimensions before modeling, we introduced a novel approach—the PCA–ANFIS model—that can predict the carbonation of reinforced concrete. Practical engineering examples were adopted to verify the superiority of the suggested PCA–ANFIS model, with 90% of the carbonation depth data used for training and 10% used for testing. The root mean square error (RMSE) values for the ANFIS, ANN, PCA–ANN, and PCA–ANFIS training were 12.23, 6.28, 5.42, and 1.38, respectively. The results showed that the PCA–ANFIS model is accurate and can be used as a fundamental tool for predicting the service life of concrete structures.

The Influence of Blast Furnace Slag on Cement Concrete Road by Microstructure Characterization and Assessment of Physical-Mechanical Resistances at 150/480 Days.

The results presented in this paper on the appropriateness of using of blast furnace slag (BFS) in the composition of roads make an original contribution to the development of sustainable materials with the aim to reduce the carbon footprint and the consumption of natural resources. The novelty of this work consists of determining the optimal percentage of BSF in road concrete, in order to: increase mechanical resistances, reduce contractions in the hardening process, and ensure increased corrosion resistances, even superior to classic cement-based mixtures. Thus, the physical-mechanical characteristics and the microstructure of some road concretes were studied in the laboratory for three different recipes. We kept the same amount of ground granulated blast furnace slag (GGBS) as a substitute for Portland cement, respectively three percentages of 20%, 40%, 60% air-cooled blast furnace slag (ACBFS) and crushed as sand substitute from now on called S54/20, S54/40, S54/60. Drying shrinkage, mechanical resistances, carbonation-induced corrosion, microstructure characterization of hardened concretes, and degree of crystallinity by SEM and XRD measurements were analyzed after a longer curing period of 150/480 days. The obtained results on the three BSF mixtures indicated a reduction of drying shrinkage and implicitly increased the tensile resistance by bending to 150 days well above the level of the blank composition. The degree of crystallinity and the content of the majority phases of the mineralogical compounds, albites, quartz, and tobermorite out of the three BSF samples justifies the increase in the compressive strengths at the age of 480 days in comparison with the test samples. Scanning electron microscope (SEM) and X-ray diffraction measurements showed the highest compactness and lowest portlandite crystal content for the S54/20 slag composite. Future research concerns are the realization of experimental sections in situ, the study of the influence of BFS on the elasticity module of road concrete, and the opportunity to use other green materials that can contribute to the reduction of the carbon footprint, keeping the physical and mechanical properties of road concrete at a high level.

Corrosion mechanism of recycled mortar prepared from CO2-treated hardened cement paste powder

CO2-treated recycled powder improves the mechanical properties of concrete. However, its corrosion mechanisms are not thoroughly understood. This study focused on the carbonation-induced corrosion mechanism of recycled mortar prepared from CO2-treated hardened cement paste powder (CCPP). First, the corrosion behavior of the steel reinforcement in a CCPP mortar (CCPPM) was evaluated using electrochemical and corrosion mass loss tests. Furthermore, the carbonation resistance of the CCPPM was quantified by testing the carbonation coefficient, and a corrosion model was established to predict corrosion. Finally, the microproperties of CCPPM and CCPP were investigated to reveal the corrosion mechanism. The results show that the corrosion rate of the steel reinforcement in the CCPPM is controlled by the combined effect of the concentration of OH– ions around the steel reinforcement and mortar porosity; the former plays a more critical role than the latter. Moreover, the variation in the w/c ratio of the CCPP base material had a slight effect on the compressive strength and carbonation resistance of the CCPPM and the corrosion rate of the steel reinforcement. The low concentration of OH– ions in the CCPPM increases the corrosion current density of the steel reinforcement by 15.91%–26.79%, consistent with the 10.96%–18.67% higher corrosion mass loss of the steel reinforcement embedded in the CCPPM cured for 540 days relative to that of the hardened cement paste powder mortar. Although incorporating CCPP increases the steel corrosion risk, the corrosion model developed herein demonstrates that CCPP can be used to guarantee a service life of 50 years for mortars when its replacement ratio is less than 20%.

Reinforced Concrete Durability Design Through a Semi-probabilistic Approach

This study provides a semi-probabilistic approach to durability design of reinforced concrete structures, subjected to carbonation-induced corrosion. The method was developed from an existing approach and using comprehensive data collated from the literature. A statistical model for predicting accelerated carbonation coefficient, using as input variables mix proportions and test conditions was also generated. The performance of the proposed method was assessed and proved appropriate. Besides delivering a more consistent semi-probabilistic method to design for the avoidance of unforeseen carbonation-induced corrosion problems, the developed statistical model to estimate the accelerated carbonation coefficient is a useful tool on the mix design, from the standpoint of conforming with the accelerated carbonation coefficients obtained through the semi-probabilistic method.

Influence of the Type of Cement on the Durability of Concrete Structures Exposed to Various Carbonation Environments in Greece: A Contribution to the Sustainability of Structures

The research objective of this paper is to investigate the effect of different types of cement and different climatic conditions on the durability of reinforced concrete structures to understand and address issues of durability and erosion. The types of cement used were CEM I 42.5N, CEM II/A-M (P-LL) 42.5N and CEM II/B-M (W-P-LL) 32.5N. Mixtures of three different cement mortars and six different concretes were prepared with these three types of cement. Cement mortars were produced according to the European standard EN 196-1. Concrete mixtures were of the strength classes C25/30 and C30/37. Concrete mixtures produced according to the specifications of the European standard EN 206 may have a shorter service life due to carbonation-induced corrosion if the choice of the cement type is not made carefully. The results indicate that the carbonation rate of concrete mixtures is significantly influenced by the type and strength class of the cement used. Using meteorological data from six regions of Greece, an empirical carbonation prediction model for these regions was obtained.