Corrosion Of Reinforcing Steel Research Articles

Comparative Analysis of Concrete Crack Detection using Image Processing and Artificial Intelligence

Cracks in concrete structures can be formed due to many reasons such as physical damage, hydraulic shrinkage, thermal shrinkage, swelling, and corrosion of steel reinforcements. These vulnerable entities present in structures are responsible for reducing the performance and strength of the concrete. Inspecting these entities and deciding the nature of these cracks is an essential element for the maintenance of the structure. Concrete crack detection based on Image Processing and Artificial Intelligence involves using computer vision techniques to automatically identify and classify cracks in concrete structures. Detection and classification of these cracks can be done using a combination of various machine learning algorithms and image processing techniques. Our project aims to detect the location of the cracks on the structures using various processing techniques such as resizing, gray scaling, binarization, segmentation, enhancement, and filtering out the noise. Detection of the cracks can be performed using thresholding techniques. Later classification of these detected cracks can be done using Deep Learning techniques concerning various deciding parameters such as length, width, and area of cross-section of the detected crack. The cracks can be classified based on their size they can be thin, medium, or wide cracks. They can also be classified based on the appearance of the crack, which may be longitudinal, vertical or transversal.

Osvrt na samozaceljujući beton - biološki pristup

Concrete is one of the most popular and used construction materials. It is strong, durable, and relatively inexpensive, but it has a higher tendency to form cracks. The cracks provide a low service life for the concrete and high maintenance costs. The penetration of aggressive ions through cracks results in corrosion of steel reinforcement, carbonation, sulphate attack, alkali-aggregate reaction, etc. However, prevention of cracks formation is impossible, however, they can be controlled or repaired by various methods. Self-healing concrete is well known as a suitable remedial method to improve concrete's long-term durability. It is a new, rapid, and environmentally friendly approach. In this technology, when concrete is exposed to water, the healing agent material produces calcium carbonate (CaCO3), which fills in the cracks and decreases permeability while enhancing concrete durability. The materials that are used as the healing agents are mostly bacteria, polymers, and chemical compounds. Bacteria are the most preferred material in concrete for healing. Therefore, bio concrete or bacterial concrete is another name for self-healing concrete. This article provides a comprehensive overview of self-healing concrete including, the system, process, mechanical properties, and durability of healed concrete.

Finite Element Analysis of Axially Loaded GFRP-Reinforced Concrete Hollow Square Columns

Hollow concrete columns are often employed in bridge constructions because of their lighter weight and effective section characteristics. In addition, to reduce the issue of steel reinforcement corrosion and create a strong and light construction, hollow section columns are also reinforced with bars made of fiber-reinforced polymer. This research aimed to analyze the effect of GFRP (glass fiber reinforced polymer) on the compression strength of hollow square concrete columns under an axial concentric load. The finite element application ABAQUS 2019 version was used to simulate a finite element model, calibrated utilizing experimental data from previous studies for various geometric models of concrete and material specifications of the reinforcement. The findings of the experimental studies and the finite element model exhibit excellent agreement. Finally, according to the parametric study's results, A parametric analysis is done to assess the impact of changing reinforcement ratio, spacing between the ties, inner-to-outer section width ratio, and a comparison with steel reinforcement. The computational results clearly show how an Increased longitudinal GFRP reinforcement ratio improves the columns' bearing capability, but when compared to steel reinforcement, it provides less bearing capability. For the optimum outcome with hollow square concrete columns, it is advised to adopt the limit of the i/o between 0.27 and 0.38. In addition, changing the spacing between stirrups was shown not to significantly impact the capacity for axial load in hollow square concrete columns.

Long-Period Grating Fiber Optic Sensors Coated With Gold Film and Pulse-Electroplated Iron–Carbon Layer for Reinforcing Steel Corrosion Monitoring

Long-Period Grating Fiber Optic Sensors Coated With Gold Film and Pulse-Electroplated Iron–Carbon Layer for Reinforcing Steel Corrosion Monitoring

The anti-degradation consequences of water repellent-based inhibitors for controlling mild steel corrosion in concrete composite

Synthetic water repellent (WRep) generally blocks the ingress of corrosive factors like moisture and various gases to the reinforced steel (RS) surface through the concrete pores. Mixing such WReps in the concrete mix did not affect the anti-corrosive response to the RS infrastructures. Considering such consequences, the present work explored the uses of two synthetic water repellents (e.g., WRep-A & WRep-B) and plant-derived green inhibitors to control the corrosion stability level of the RS in the concrete matrix. The broader question of the work is to know whether the water-repellent affects the anti-degradation response to the steel in concrete at the same patterns as commonly practiced in the concrete matrix or differently when the cast reinforced concretes exposed to water-repellent suspension for a certain curing time. The concrete slab exposed for one week to the suspension mixture of 1000 ppm WRep-B+Mangifera indica (WRep-B+MILE) and 1000 ppm WRep-B+Psidium guajava (WRep-B+PGLE) extracts exhibited maximum anti-corrosive response, which is justified by corrosion potential shifting to a more positive potential zone where the reinforced steel corrosion damage state rated as <10% probability and anticipated more effective corrosion inhibiting activities compared to other concentrations used in this work.

Real-time monitoring of residual strength in corroding steel reinforcement using ultrasonic-guided waves and multi-physics modelling

Corrosion-induced material strength degradation is a major threat to the service life of reinforced concrete (RC) structures. Continued mass loss and pit formation after the initiation of corrosion in reinforcing steel consequently results in strength degradation. In this study, a non-destructive structural health monitoring (SHM) approach using ultrasonic guided waves with multi-physics modelling to monitor and forecast strength degradation of corroding steel is presented. Surface-bonded piezoelectric wafer transducers (PWTs) are used for actuating and sensing of guided waves in order to correlate the group velocity and amplitude of flexural wave modes with the strength reduction. The major findings of the work are presented in the form of empirical relationships between guided wave characteristics with reduced yield, ultimate, and buckling strength of corroded steel. It is observed that for a rebar of 12 mm diameter having slenderness ratio between 8 and 10, a 10% increase in amplitude and 8.44% increase in group velocity of flexural mode for corroding steel indicates a corresponding reduction of 10.278% in yield strength, 10.277% in ultimate strength, and 4.45% in buckling strength in progression phase of corrosion. A multi-physics numerical model of corrosion in RC structures that considers the effect of local exposure and environment is then elucidated with deviation less than 6.34% from experimental results in order to forecast the mass loss. The presented data fusion strategy, which combines guided wave-based monitoring and multi-physics modelling finds valuable application in assessing the current state of degradation in structural performance and strength-based service life prediction.

Resistance of Concretes to External Chlorides in the Presence and Absence of Sulphates: A Review

Corrosion of steel reinforcement due to chloride attack remains a major reinforced concrete durability concern. The problem is prevalent for concrete structures located within marine environments or frost-prone locations where chlorides containing de-icing salts are used. This paper is a state-of-the-art review into chloride binding in Portland cement concrete, with consideration of the differences induced by the presence of sulphates, such as found in seawater. The review also considers the use of supplementary cementitious materials (SCMs), the use of which has increased because of their potential to enhance durability and reduce the carbon footprint of concrete production. Such materials impact on phase assemblage and microstructure, affecting chloride binding and transport properties. Therefore, field and laboratory studies are critically reviewed to understand how these could help in the design of more durable concretes. The contributions of chloride binding, hydrate compositions and microstructures of the binding materials affecting chloride transport in concretes are also evaluated to suggest a more robust approach for controlling the problem of chloride attack.

Maintenance interventions period of existing RC motorway viaducts located in moderate/high seismicity zones

Considering the recent collapses which have affected several existing reinforced concrete (RC) motorway bridges, the correct maintenance interventions planning of these strategic infrastructures has acquired increasing importance to maintain a suitable safety level even in case of seismic loads. One of the most important problems which influences the structural performance of existing RC motorway bridges is the presence of corrosion which may affect the bearing-capacity members. In particular, the corrosion of steel reinforcement of the piers due to the carbonation phenomenon is strictly related to the seismic performance of these structures as the viaducts of the Italian motorway networks realized around the 1970s.In this paper, the evaluation of the seismic vulnerability of three existing RC motorway bridges has been developed using non-linear time history analysis. Three corrosion scenarios (slight, moderate and high) have been analysed. The effects of the carbonation, expressed in terms of piers steel rebars area reduction, have been considered as a function of the age of the viaduct. Risk indices calculated as the ratio of the peak ground acceleration leading to collapse of the first structural element and the design peak ground acceleration, are useful to optimize the scheduling of the motorway networks maintenance interventions.

The effect of carbonation on chloride redistribution and corrosion of steel reinforcement

Desalinated sea sand concrete (DSSC) is increasingly used to mitigate the shortage of natural river sand. However, one major concern lies in the corrosion risks of steel reinforcement embedded in DSSC under combined chloride and carbon dioxide attacks. To understand the corrosion mechanism, the corrosion process of steel reinforcement embedded in the cement paste containing chloride ions (Cl−) was monitored by electrochemical measurements, during which pH, Cl− profile and corrosion products were examined simultaneously. Raman spectroscopy was employed to evaluate the carbonation depth in microscale. Tests results showed that corrosion was initiated before the carbonation front reached the steel reinforcement. Interestingly, it was the carbonation-induced Cl− redistribution rather than the decrease of pH that dominated the corrosion initiation. Before the carbonation front, a Cl− accumulation zone was identified, and the corrosion mechanism was revealed. This study shall advance the understanding of the corrosion of steel reinforcement in DSSC for durability design of reinforced concrete structures.

Nghiên cứu chế tạo cảm biến điện hóa galvanic giám sát trạng thái ăn mòn cốt thép trong môi trường xâm thực bởi ion clorua

This paper presents the results of a study on the corrosion of steel reinforcement in concrete pore solutions contaminated with chloride ions. With increasing chloride concentration, the open-circuit potential and the anodic polarization curve shift towards more negative potential values, the passive potential region of the anodic polarization curve decreases. The corrosion rate of reinforcement was evaluated according to the linear polarisation resistance technique. Accordingly, the corrosion rate of steel reinforcement is 4.53 µA/cm2 in the solution containing 1 M Cl-. In this study, galvanic electrochemical sensors with low carbon steel anodes and copper cathodes were developed. In an environment with no or low Cl- concentration, where the reinforcement is passivated, the corrosion current density of the sensor does not exceed 10.0 µA/cm2. The corrosion current of the sensor increases sharply under cathodic control with increasing chloride content. Thus, the developed sensor has a high sensitivity to chloride corrosion and is capable of detecting pitting corrosion caused by chlorides at an early stage.

Determination of the degree of microbiological damage to the «Cement Concrete - Steel Reinforcement» system

The degree of corrosion damage by microorganisms to the concrete wall of the basement is investigated. The biofilm on the surface of the concrete wall under study is formed by micromycetes Aspergillus niger, bacteria Bacillus subtilis, Actinomycetes, nitrifying bacteria Nitrosomonas, lactic acid bacteria Lactobacillus and sulfate-reducing bacteria Desulfovibrio. The waste products of microorganisms consist of organic acids secreted by micromycetes of Aspergillus niger, ammonium ions, carbonate-, nitrate-, sulfide-ions secreted by bacteria. To establish the corrosion state of steel reinforcement in biodegradable concrete, the electrode potential was measured. The established values of the surface potential of steel reinforcement are in the range -351 ÷ -376 mV. This suggests that the probability of local corrosion of steel reinforcement in a biodegradable concrete wall is strong. It will take about 20 years to achieve an aggressive concentration of organic acids at the surface of steel reinforcement in biodegradable concrete with a layer thickness of 5 cm. However, in conditions of constant moistening of the concrete surface, this period is reduced to 10-11 years. The predicted rate of local corrosion of steel reinforcement in concrete exposed to microorganisms is at least 0.2 mm/year. It was found that the depth of concrete destruction under the influence of microorganisms, mainly micromycetes Aspergillus niger, for 20 years is 1.3 cm; for 50 years is 2.1 cm.

Flexural Behaviors of Modified Recycled Aggregate Concrete Reinforced with Pultruded GFRP

Corrosion of steel reinforcement in underwater concrete structures continues to be a problem in the modern era. The possibility of employing pultruded glass fibre reinforced polymer (GRFP) I beams to replace traditional steel reinforcement in an encased beam is still being explored. The purpose of this research is to further investigate the effects of incorporating treated recycled concrete aggregate (RCA) and discrete synthetic fibres, specifically Polyolefin (PO) and Fibrillated Polypropylene (PP) fibres, in the production of concrete beam reinforced with GFRP I beam for underwater construction. Five beams were constructed and tested in this investigation using a four-point loading arrangement. The load–deflection curve, stress–strain curve, and initial and ultimate fracture loads are all included in the test parameter set. The results indicate that treating RCA and fibres greatly increases the flexural capacity of modified recycle aggregate concrete (RAC) beams compared to unmodified RAC beams.

Enhancing Sustainability of Corroded RC Structures: Estimating Steel-to-Concrete Bond Strength with ANN and SVM Algorithms

The bond strength between concrete and corroded steel reinforcement bar is one of the main responsible factors that affect the ultimate load-carrying capacity of reinforced concrete (RC) structures. Therefore, the prediction of accurate bond strength has become an important parameter for the safety measurements of RC structures. However, the analytical models are not enough to estimate the bond strength, as they are built using various assumptions and limited datasets. The machine learning (ML) techniques named artificial neural network (ANN) and support vector machine (SVM) have been used to estimate the bond strength between concrete and corroded steel reinforcement bar. The considered input parameters in this research are the surface area of the specimen, concrete cover, type of reinforcement bars, yield strength of reinforcement bars, concrete compressive strength, diameter of reinforcement bars, bond length, water/cement ratio, and corrosion level of reinforcement bars. These parameters were used to build the ANN and SVM models. The reliability of the developed ANN and SVM models have been compared with twenty analytical models. Moreover, the analyzed results revealed that the precision and efficiency of the ANN and SVM models are higher compared with the analytical models. The radar plot and Taylor diagrams have also been utilized to show the graphical representation of the best-fitted model. The proposed ANN model has the best precision and reliability compared with the SVM model, with a correlation coefficient of 0.99, mean absolute error of 1.091 MPa, and root mean square error of 1.495 MPa. Researchers and designers can apply the developed ANN model to precisely estimate the steel-to-concrete bond strength.

Effect of coarse aggregate size on corrosion of reinforced concrete exposed to carbonation and chloride ingress by electrochemical measurements

This article evaluated the application of electrochemical techniques to assess the degree of corrosion of reinforcement steel in concrete exposed simultaneously to carbonation and chloride ingress. After carbonation accelerated at 3 different levels, the reinforcement corrosion was accelerated by the ionic migration of chlorides. Subsequently, the electrochemical techniques (Rp, cyclic voltammetry, EIS) were applied to the specimens at 40 months of age. Chloride penetrations above 20 mm showed a remarkable drop in steel durability. In this condition, the disappearance of the stability region in the voltammograms and an increase in the capacitive arc of the impedance spectra were identified. The intensification of carbonation reduced the Rp. Concretes with 25 mm coarse aggregate had the worst results in the electrochemical tests since the sharp drop in the phase angle during EIS tests indicates a concrete/reinforcement interface incapable of retaining electrical charges, with a low resistance to corrosion progress. The results of mass loss supported this statement.

Investigating the Bond Strength of FRP Laminates with Concrete Using LIGHT GBM and SHAPASH Analysis.

The corrosion of steel reinforcement necessitates regular maintenance and repair of a variety of reinforced concrete structures. Retrofitting of beams, joints, columns, and slabs frequently involves the use of fiber-reinforced polymer (FRP) laminates. In order to develop simple prediction models for calculating the interfacial bond strength (IBS) of FRP laminates on a concrete prism containing grooves, this research evaluated the nonlinear capabilities of three ensemble methods-namely, random forest (RF) regression, extreme gradient boosting (XGBoost), and Light Gradient Boosting Machine (LIGHT GBM) models-based on machine learning (ML). In the present study, the IBS was the desired variable, while the model comprised five input parameters: elastic modulus x thickness of FRP (EfTf), width of FRP plate (bf), concrete compressive strength (fc'), width of groove (bg), and depth of groove (hg). The optimal parameters for each ensemble model were selected based on trial-and-error methods. The aforementioned models were trained on 70% of the entire dataset, while the remaining data (i.e., 30%) were used for the validation of the developed models. The evaluation was conducted on the basis of reliable accuracy indices. The minimum value of correlation of determination (R2 = 0.82) was observed for the testing data of the RF regression model. In contrast, the highest (R2 = 0.942) was obtained for LIGHT GBM for the training data. Overall, the three models showed robust performance in terms of correlation and error evaluation; however, the trend of accuracy was obtained as follows: LIGHT GBM > XGBoost > RF regression. Owing to the superior performance of LIGHT GBM, it may be considered a reliable ML prediction technique for computing the bond strength of FRP laminates and concrete prisms. The performance of the models was further supplemented by comparing the slopes of regression lines between the observed and predicted values, along with error analysis (i.e., mean absolute error (MAE), and root-mean-square error (RMSE)), predicted-to-experimental ratio, and Taylor diagrams. Moreover, the SHAPASH analysis revealed that the elastic modulus x thickness of FRP and width of FRP plate are the factors most responsible for IBS in FRP.

Long‐term shear strength of RC beams based on a mechanical model that considers reinforcing steel corrosion

AbstractCorrosion of stirrups (generally with small diameters and concrete covers) significantly affects the shear strength of reinforced concrete elements. As shear failures may lead to brittle collapses, hence the need to avoid them during structures' entire service life. The Compression Chord Capacity Model (CCCM), a shear mechanical model, was recently extended to predict the strength of corrosion‐damaged beams by identifying the model parameters that could be most affected by steel corrosion. In this paper, the CCCM is combined with two material deterioration models included in the new Spanish Structural Code, and considers carbonation of concrete or chloride ions, to predict long‐term shear strength evolution. Finally, a parametric analysis is carried out to explore the effect of the most influential parameters on shear strength degradation according to the used models and depending on different exposure classes.

Mechanisms in Long-Term Marine Corrosion of Steel Reinforcement in Concretes

This paper is concerned with the mechanisms governing reinforcement corrosion in concretes in marine environments and how they influence the manner of local failure of the concrete. Despite the high pH of the concrete, air voids from inadequate concrete compaction can, under chloride conditions, produce localized pitting corrosion of adjacent steel bars. This may continue, under the hydrogen evolution cathodic reaction with the build-up of rusts causing localized concrete failure, followed by exposure of the steel to the environment, removal of the elevated concrete pH, and a subsequent much higher rate of corrosion. A completely separate deterioration process is the gradual dissolution and loss of concrete alkalis with time. This can lower the concrete pH sufficiently to permit general corrosion of steel to be thermodynamically feasible, it increases concrete permeability and it facilitates access to the environment to permit corrosion by oxygen reduction. The two processes produce different types of concrete failure. Examples drawn from actual reinforced concrete structures are given and the mechanisms explained, including the often-observed build-up of FeOOH-type rusts on the outside of magnetite rust layers well inside concretes. The implications that follow and research needs are discussed.

Repairing Materials for Different Post Fire - Damaged Structural Concrete Members: A Critical Review

When concrete structures are exposed to elevated temperatures or fire, their strength begins to degrade. The major problem is that the structure induces cracks, which let the aggressive material enter the concrete and the steel reinforcement corrosion. Therefore, the damaged member should have been strengthened or repaired; sometimes, the repair is chosen over demolition because it is more economical. Researchers used materials to repair heat-damaged concrete, such as fiber-reinforced polymer (FRP) composites, shotcrete, ferrocement, epoxy resin mortar, and fiber-reinforced concrete. The compatibility of these materials should be investigated, for example, the bond strength between repair material and substrate. Ferrocement can restore stiffness and toughness, while a structure with FRP jacketing cannot regain stiffness. Reviewing post-fire strength and repairing materials has not been done; therefore, this study highlights the strength loss of fire-damaged concrete and the repaired structure's confinement.

Theoretical Prediction of Two-Peak Behavior of GFRP-Reinforced Concrete Compressive Members

The use of fiber-reinforced polymer (FRP) composites in compressive members is advantageous to reinforced concrete structures in order to alleviate the problem of corrosion of steel reinforcement and to produce a lightweight and efficient structural element. This investigation aims to propose the theoretical models for capturing the axial loading capacity (ALC) of hollow concrete columns (HCCs) having main FRP rebars and transverse FRP spirals. All the glass-FRP-reinforced HCCs portray two-peak load performance. The first peak is due to the gross cross-sectional area of concrete while the second peak is due to the core material laterally wrapped with FRP spirals. For the prediction of the first peak load of HCCs which is equal to the maximum capacity of solid concrete columns, a database of 279 FRP-reinforced columns was produced from the previous research and the ALC models were suggested; one for capturing the first peak and the other for estimating the second peak ALC of HCCs. The predictions of proposed models were compared with the test results from the literature. A close relationship was perceived between the theoretical and experimental results.

Experimental study of dynamic bond behaviour between corroded steel reinforcement and concrete

Corrosion damage of steel reinforcement is detrimental to the load-carrying capacity of reinforced concrete structures because it not only reduces the cross sectional area and strength of reinforcement bars, but also weakens the bond between reinforcement and concrete. Many studies have investigated the effects of corrosion on reinforcement loss and static bond strength between reinforcement and concrete, but no study of the influence of corrosion damage on dynamic bond strength has been reported yet. In this study, laboratory tests were conducted to investigate the effect of corrosion on the bond behaviour between steel reinforcement and concrete subjected to high rate dynamic load. Accelerated corrosion damage was induced to steel bars embedded in concrete specimens under laboratory condition. The bond parameters of steel reinforcement and concrete including the ultimate bonding load and bond-slip relationship corresponding to the various strain rates and corrosion degrees were obtained through dynamic pull-out tests. The empirical formulae of dynamic increase factors (DIFs) of the ultimate bonding strength corresponding to different corrosion levels and strain rates were proposed. The experimental results show that the strain rate effect on bonding behaviour is prominent irrespective of the corrosion level. The increase in the ultimate bonding strength with strain rate for the heavily corroded reinforcement (η = 5 %-10 %) is more prominent than that for the slightly corroded reinforcement (η = 0 %-5%). The decrease in the ultimate pull-out force caused by the corrosion damage at high strain rate is more pronounced than that at low strain rate. Corrosion-induced crack and the tensile strength of concrete have significant effect on both the static and dynamic bond behaviours. The results presented in the paper can be used for better modelling and prediction of the responses of corroded reinforced concrete structures subjected to dynamic loads.