Half-cell Potential Measurements Research Articles

Utilizing Electrochemical Techniques for Assessing the Probability of Concrete Resistivity and Corrosion Potential in Reinforced Concrete Structures

Corrosion of reinforcing steel is a major durability issue for reinforced concrete structures exposed to aggressive environments. Early assessment of corrosion probability is important for effective maintenance planning. This study investigates the application of non-destructive electrochemical methods like concrete resistivity and half-cell potential measurement, along with integrated assessment and advanced techniques, for evaluating corrosion risk in reinforced concrete. Concrete specimens with and without Albizia amara resin coating were subjected to accelerated corrosion testing. Concrete resistivity and half-cell potential values showed an inverse correlation, with lower resistivity indicating higher corrosion risk. Resistivity and potential results for the coated samples exhibited intermediate values compared to the control and corroded samples, demonstrating the resin's partial passivating effects. Rebar diameter measurements before and after exposure confirmed corrosion led to reductions in diameter and cross-sectional area, which coating mitigated. Statistical analysis validated the significant impacts of original bar diameter and corrosion level on subsequent geometry changes. Mechanical testing of reinforcing steel bars found the control samples had the highest strength and ductility, while the coated bars exhibited properties closer to the controls than the corroded bars. The protective capabilities of the bio-based Albizia amara resin coating were validated through multipoint monitoring of material durability parameters. Overall, results demonstrated the effectiveness of integrated electrochemical testing with non-destructive techniques for comprehensive condition assessment and corrosion risk evaluation in reinforced concrete structures

Mitigation of Steel Corrosion Threshold Utilizing Plant-Based Green Corrosion Inhibitors through Electrochemical Techniques

Corrosion of steel reinforcement is a major cause of deterioration in reinforced concrete structures. The corrosion process is influenced by the concrete-steel interface, with the alkaline concrete pore solution initially providing passivation. However, ingress of aggressive substances like chlorides can disrupt the passive layer, initiating active pitting corrosion above a threshold level often taken as 0.4% chloride by cement weight. Once the chloride threshold is exceeded, corrosion propagation depends on oxygen and moisture availability. The resulting rust formation causes expansive cracking and spalling of the concrete cover. Corrosion damage can be mitigated through use of inhibitors like calcium nitrite though high dosages impair concrete strength. Recently, plant-based organic compounds have shown promise as green corrosion inhibitors. The corrosion behavior of steel in concrete can be evaluated through impressed accelerated corrosion testing along with electrochemical techniques like half-cell potential mapping and resistivity measurements. These allow assessment of the probability of corrosion and corrosion rate. Techniques like linear polarization resistance and electrochemical impedance spectroscopy can also quantify instantaneous corrosion rate. Proper structural condition assessment and repair using both conventional and green inhibitors is crucial to control steel corrosion, maintain service life and ensure safety. Further research is needed on green corrosion mitigation methods and advanced non-destructive testing techniques.

A comparative analysis of corrosion assessment techniques for steel in reinforced concrete exposed to brine water environments

Abstract Corrosion assessment of steel-reinforced concrete specimens submerged in synthetic brine water with various chloride concentrations for 1–16 weeks was performed. Mass loss measurements combined with electrochemical techniques – half-cell potential, linear polarization (LP), and electrochemical impedance spectroscopy (EIS) – were employed. The results obtained from all corrosion assessments – on-site testing (half-cell potential measurements), laboratory scale (LP and EIS measurements), and destructive testing (mass loss or immersion measurements) – exhibited remarkable consistency, complementarity, and mutual supportiveness. Corrosion rate (CR) values from mass loss were close to those obtained from LP and EIS. The corrosion resistance decreased with increasing chloride concentration and immersion time, as indicated by the highest CR, Ca2+, and Fe2+ concentrations, and the lowest half-cell potential and polarization resistance. X-ray photoelectron spectroscopy investigation on the corroded steel surface revealed Fe(III) oxides and hydroxides and Fe(III) (FeCl3), corresponding to the reduction in polarization resistance in the LP and EIS results.

Social Parameter’s Role in BEM-PSO-Based Inverse Analysis for Locating Corrosion of Reinforced Concrete

The objective of this research is to investigate the effect of social parameter on the performance of boundary element inverse analysis (BEIA) to determine the location of reinforcing steel corrosion in concrete. BEIA was constructed by integrating the Boundary Element Method (BEM) and Particle Swarm Optimization (PSO) (PSO). BEM was used to calculate the corrosion potential on the whole surface of reinforced concrete. The cost function for detecting corrosion of reinforcing steel in concrete was evaluated using PSO. BEIA was conducted with 15 electrical potential data on the surface of reinforced concrete as a reference, such as from half-cell potential measurement. Numerical simulations of reinforced concrete with a single reinforcement reveal a difference in the speed of BEIA in locating corrosion sites. The higher the social parameter value, the faster the particles tend to migrate. However, if the parameter value is too high, the number of iterations required for the particles to converge increases, which has a negative effect on locating the corrosion point. Consequently, the variation of the social parameter affects the performance of BEIA in detecting the location of corrosion in reinforced concrete.

Evaluation of the Corrosion Activity of Reinforcement in Drainage Gallery of Concrete Dam using Half-cell Potential (HCP)

Dams are essential structures for water management, providing various benefits crucial for human survival and economic growth. However, steel corrosion in concrete dams poses a significant threat, leading to structural deterioration and potential collapse. Detecting corrosion in the early stage is critical to prevent catastrophic failures. This study investigates corrosion risk in a concrete dam's drainage gallery using half-cell potential (HCP) measurements, a common method for assessing corrosion activity in reinforced concrete. The electrochemical process of steel corrosion in concrete, influenced by factors like chloride or carbonation exposure and temperature, is discussed. The HCP method is a nondestructive technique for determining the corrosion rate of steel reinforcement in concrete structures. It involves measuring the potential difference between reinforcing steel and reference electrodes; typically, a copper/copper sulphate electrode is used. The potential difference between the two electrodes is then used to calculate the corrosion rate of the reinforcing steel. The HCP method is a reliable and cost-effective way to identify potential corrosion problems before they become severe. The present study used CorMap II® to measure HCP on the upstream face of the dam's drainage galleries. Results indicate predominantly low corrosion risk across tested locations, with minimal uncertainty. However, interpretations must consider environmental factors' influence on measurements. The study's findings offer valuable insights for future corrosion assessments and underline the importance of preventive measures for concrete dam integrity.

Integrating Data from Multiple Nondestructive Evaluation Technologies Using Machine Learning Algorithms for the Enhanced Assessment of a Concrete Bridge Deck

Several factors impact the durability of concrete bridge decks, including traffic loads, fatigue, temperature changes, environmental stress, and maintenance activities. Detecting problems such as corrosion, delamination, or concrete degradation early on can lower maintenance costs. Nondestructive evaluation (NDE) techniques can detect these issues at early stages. Each NDE method, meanwhile, has limitations that reduce the accuracy of the assessment. In this study, multiple NDE technologies were combined with machine learning algorithms to improve the interpretation of half-cell potential (HCP) and electrical resistivity (ER) measurements. A parametric study was performed to analyze the influence of five parameters on HCP and ER measurements, such as the degree of saturation, corrosion length, delamination depth, concrete cover, and moisture condition of delamination. The results were obtained through finite element simulations and used to build two machine learning algorithms, a classification algorithm and a regression algorithm, based on Random Forest methodology. The algorithms were tested using data collected from a bridge deck in the BEAST® facility. Both machine learning algorithms were effective in improving the interpretation of the ER and HCP measurements using data from multiple NDE technologies.

Multi-Reference Electrode Lithium-Ion Pouch Cell Design for Spatially Resolved Half-Cell Potential and Impedance Measurements

Reliable experimental methods for measuring local potentials in lithium-ion battery cells are challenging but vital for a deep understanding of internal processes at the individual electrode level, and to parameterize and validate electrochemical models. Different three-electrode setups and reference electrodes (REs) have been developed in recent years. Some are based on custom laboratory setups or are small, e.g. coin cell sized. This work addresses internal potentials and half-cell impedances in the widely used single-layer pouch (SLP) cell format and proposes a novel multi-reference electrode cell design, enabling spatially resolved measurements. For the first time, it is shown how multiple 25 μm and 50 μm thin gold wire REs, together with a larger LTO-RE, can be used to study occurring inhomogeneities, considering the geometrical anode overhang. Special attention is given to the subtleties of the measurements and their interpretation. Multiple REs allow plausibility checks and confirm stability for both types during a continuous measurement period of more than 7,500 h (>10 months), demonstrating suitability, e.g. for long-term cycling measurements. Results from electrochemical impedance spectroscopy (EIS) and half-cell potential measurements at low currents of C/100 and during fast charging at up to 3C highlight the versatility of the easily reproducible cell design.

Hands-On Training of Non-destructive Testing Using a Mock-Up in the Curriculum of Civil Engineers

ABSTRACT Our infrastructure deteriorates progressively and the knowledge about the current condition is crucial to enable proper maintenance. Nondestructive techniques provide the basis for reliable condition assessment and thus, requires talented engineers with corresponding skills. Fortunately, in the curriculum of civil engineers, nondestructive testing gains more and more importance. The challenge in teaching nondestructive testing is to fulfil the requirement that students achieve the learning objective of “Application.” The term “Application” describes the ability that students are able to use nondestructive techniques appropriately. This teaching objective is not achievable in classroom lectures. Thus, the authors developed a mock-up for hands-on learning where students can try several nondestructive techniques such as half-cell potential measurement, Radar, ultrasound, impact-echo etc. Civil engineering students often encounter difficulty with the handling of sometimes very sophisticated devices. The challenge increases even more when the students have to extract the measured data, evaluate them, and relate their results to the condition of the tested object. With the support of the mock-up the authors intended to assist civil engineering students to understand the application of nondestructive techniques. This paper presents the design of the mock-up in combination with the corresponding teaching concept and the first teaching experience.

Feasibility study of amperometric and electrochemical quartz crystal microbalance measurements for in situ state of charge monitoring in vanadium flow batteries

For an efficient flow battery operation, knowledge of the state of charge of the battery is essential. Monitoring the state of charge of both half cells is advantageous concerning a timely detection of crossover processes. We present the first results for amperometric and electrochemical quartz crystal microbalance measurements in a vanadium flow battery test setup. By validating with half cell potential measurements as well as ex situ titration we investigate the applicability of both electrochemical methods for an in situ half cell state of charge monitoring.

Corrosion Assessment Methods in Reinforced Cement Concrete

Worldwide huge amount was spent on infrastructure development projects, in which a major part is spent on demolishing deteriorated structures due to their reduction in serviceability due to various external factors. This may be attained by preventing reinforced cement concrete (RC) structures from factors that affect serviceability such as corrosion. The research community is developing various techniques to predict corrosion in RC structures to prevent the structure in the initial stages by carrying out maintenance work instead of going for the reconstruction of deteriorated structures. The corrosion of RC structures was mainly caused by chloride ions penetrating the structure or by carbonation. This coefficient can be used to predict the rate of corrosion in concrete. Electrochemical measurement, Eddy current, Half-cell potential measurement, etc., are the experimental techniques to forecast the corrosion rate in concrete reviewed. Recently various software’s like Life 365, Thermos calc, Concrete Compass, etc., were developed to predict the corrosion rate in RC structures. This research paper reviews the effectiveness of the application of software to predict corrosion rate in RC structures by reviewing previous research works to identify an accurate method to be followed.

Corrosion of steel rebars embedded in One-part Alkali activated concrete mixes

To reduce CO2 emissions and turn a variety of industrial/agricultural wastes into valuable cementitious products, alkali-activated materials (AAM) are recognized as suitable substitutes for regular Portland cement (OPC). However, the concentrated aqueous alkali solutions used in conventional two-part alkali activated materials are highly corrosive, viscous, and are difficult to handle in direct field applications. As a result, the potential for developing so-called "just add water" type one-part AAMs, as compared to traditional two-part AAM, is being explored, particularly in cast-in-situ applications. In the present study on corrosion of reinforcing steel bars in fly ash-slag (FA-GGBS) based one-part AAC mixtures, three parameters—the total binder content, the relative proportions of GGBS and Fly-ash and the percentage of sodium oxide (Na2O) - are recognized as the key factors in determining the strength and durability performance (including corrosion of rebars embedded in it) of a given AAC mix. Accordingly, experiments were conducted on AAC mixes with three binder contents (440, 460, and 480 kg/m3), three Slag/FA ratios (80/20, 70/30 and 60/40, by volume) and three alternate Na2O percentages (5, 6, and 7%, by weight of total binder content). Prismatic cylindrical test specimens of reinforced geopolymer concrete were prepared and half-cell potential and corrosion rate measurements were made after 28-, 56-, and 90 days of continuous exposure to 3% of NaCl solution, to accelerate the corrosion process. Measured corrosion current density and corrosion rates using a Electro-chemical Corrosion Analyser have indicated that the AAC mixture having a total binder content 440 kg/m3, GGBS/FS ratio of 70/30 and 6% Na2O content, exhibits best corrosion resistance amongst the various mixes tested herein, as measured up to the end of 90-days.

Mechanical strength and durability analysis of mortars prepared with fly ash and nano-metakaolin

Pozzolans such as fly ash (FA) and nano-metakaolin (MK) are the two industrial wastes that have attracted the attention of researchers due to their pozzolanic action that improves the performance of cementitious materials in an aggressive environment and can reduce global cement demand and lessen the emission of greenhouse gases. This study analyzes the strength and durability properties of cement mortar with partial substitution of cement with MK in the presence of FA. The effect of substitution of MK in binary and ternary blends on strength and durability has been studied by varying the dosage of FA (5‐20%) as well as MK (2.5‐10%) and optimization of MK content has been carried out. A comparative analysis of beneficial aspects of FA and MK, along with their combination in optimized content at a fixed water/binder ratio of 0.5, has also been performed in terms of corrosion resistance through electrical resistivity and half-cell potential measurements. Further, the results have been correlated by microstructural analysis. The study reveals a significant increase in strength and durability of mortar at a dosage of 10% FA+7.5% MK with an increase in chloride, sulfate and corrosion resistance due to improved microstructure owed to the better pozzolanic action of the substituents with synergistic action. Thus, the partial substitution of cement with optimized content of MK (7.5%) in the presence of FA (10%) can not only help in solid waste management but can also reduce the cement consumption leading to sustainable construction.

Inspecting the corrosion state of underground reinforced concrete structures

Unnoticed corrosion in underground reinforced concrete structural members – such as foundations, retaining walls, or piles – may severely threaten the integrity of structures. However, condition assessment of the ground-buried structural parts is challenging, because the areas of interest are hardly accessible for visual inspection or non-destructive testing. An example of particular practical relevance is reinforcement corrosion at the back-side of the lower end of cantilever retaining walls, near the construction joint between stem and heel of the base slab. The collapse of a cantilever retaining wall in Austria was a tragic reminder of the dangers of unnoticed corrosion. The drawback of current inspection methods is that they are laborious and costly, but still, only a tiny fraction of the structure can be inspected. Considering that the degree of corrosion can vary significantly along a structure, such local information includes a risk that corrosion elsewhere remains undetected.A novel inspection system is proposed here, combining the well-proven half-cell potential measurement technique with steered horizontal underground drilling technologies. With this approach, a tailor-made probe is brought in proximity to the concrete surface in the soil and electrochemical measurements are performed to characterize the corrosion condition. The main advantage is that virtually the entire length of the structure can be inspected, thus overcoming the limitations of highly local inspection. Moreover, the proposed technique includes a method to constantly monitor the functionality of the potential measuring probe, based on electrical resistance measurements. The feasibility of the approach was confirmed in laboratory experiments on a mortar block in soil. These findings were confirmed in a field experiment. The results suggest that local corroding zones of practice-relevant size can be detected for a distance between the reference electrode and the steel surface of at least 25 cm. On the basis of this work, underground corrosion inspection of cantilever retaining walls is considered feasible, and the development of similar technologies as the one proposed here may in the future considerably enhance condition assessment of structures buried in the ground.

Spatial variability of half-cell potential data from a reinforced concrete structure—a geostatistical analysis

Corrosion in reinforced concrete structures is among the major degradation mechanisms. The quantification and description of the spatial distribution of the corrosion condition within a structure on the basis of condition assessments are important. This study considered half-cell potential mapping data as a widely used technique to detect corrosion in reinforced concrete structures. A four-step workflow was proposed to analyse half-cell potential data with geostatistical techniques, first consisting of trend identification and possible trend removal. The obtained residuals were then subjected to a quantile-quantile transformation. Subsequently, experimental variograms were calculated and fitted with variogram models to estimate the correlation lengths. A case study with data from a road tunnel confirms the applicability of the workflow. It was assumed that the identified trend is primarily a result of the heterogeneity of the exposure conditions within the structure that ranges several metres. The residuals are interpreted as the result of the heterogeneities of material resistances that give rise to spatial variability in corrosion probability on a shorter distance range. The proposed analysis may be utilised for service life modelling (e.g. based on random fields), planning maintenance works, or optimising the grid size for half-cell potential measurements.

Corrosion resistance behaviour of concrete containing treated used foundry sand

In the last two decades, the scientific community, by the efforts of researchers, has witnessed many attempts to find alternative materials for natural sand using industrial waste materials instead of natural river sand, with a major goal of preserving the natural environmental resources. One of the industrial waste materials, is Used Foundry Sand (UFS), which is processed and used in concrete as a partial replacement for fine aggregate as Treated Used Foundry Sand (TUFS). The precise and all-inclusive investigation on the corrosion resistant characteristics of TUFS blended concrete is very scant. Therefore, experimentations were conducted to study the corrosion resistance performance of TUFS as partial replacements for fine aggregate. TUFS were substituted for fine aggregate in different weight percentages. The reinforced concrete specimens were casted to 5% NaCl under accelerated corrosion process. Apart from half-cell potential measurement, impress current techniques were employed to assess rebar corrosion, and microstructural analysis was carried out using X Ray Diffraction (XRD). According to test results, TUFS concrete has better corrosion resistance qualities than control concrete, paving the way for high-quality concrete production.

Evaluation of Half-Cell Potential Measurements for Reinforced Concrete Corrosion

The evaluation of half-cell potential measurements in reinforced concrete (RC) members can be a key issue for civil engineers. The primary reason for this is that the interpretation of half-cell potential measurements based on the available standards provides information related only to the possibility of corrosion in concrete, but it does not provide a clear perception of the influence of corrosion on the capacity of the RC members. The objective of this study is two-fold: (1) to explore the influence of corrosion level on the flexural capacity of RC members; and (2) to provide engineers with a better understanding of the correlation between half-cell potential measurements and flexural capacity of RC members. To establish this, twelve RC beams were cast and then exposed to accelerated corrosion utilizing an impressed current. After that, half-cell potential tests were performed on the entire surface of the beams. Next, a four-point loading test was performed on the beams to determine their flexural behavior. The analysis of measurements showed that there is a high positive correlation between the half-cell potential measurements and the flexural capacity of the tested beams which demonstrates the potential of half-cell measurements to predict the capacity degradation level of the RC beams due to corrosion.

Study of dynamic half-cell potential signal of rock bolt under stray current interference based on probabilistic-based method

Dynamic stray current leads to severe electrochemical corrosion on rock bolt in large cross-section subway tunnel. It’s important to evaluate the corrosion risk of corroded rock bolt based on monitoring signal. In this paper, an experiment for half-cell potential measurement of rock bolt under dynamic stray current interference was carried out. Tested non-stationary half-cell potential signal was analyzed the dynamic characteristics of half-cell potential in time and frequency domain. Herein, two parameters: potential shift ΔE and time ratio rt, were put forward to capture the characteristics of half-cell potential signal. A probabilistic-based analysis method was therefore proposed to quantify the corrosion risk of non-stationary half-cell potential, in which PDF of potential shift signal was fitted by generalized extreme value (GEV) function and kernel density estimation (KDE) technique. It is found that location parameter μ in GEV and the sum of the absolute values of the PDF derivative Sd could effectively represent potential shift and time ratio in half-cell potential signal respectively.

The Influence of CaCl2-Blended Acrylic Polymer on Steel Rebar Corrosion and Acid Attack Resistance of Mortar

A realistic forecast of the impact of CaCl2-blended acrylic polymer (CP) emulsions on steel reinforcement corrosion is difficult without a detailed study. This is traceable to the conflicting effects of cement additives on the chloride threshold value, pore solution chemistry, and matrix resistivity. Hence, in the study reported herein, the actual influence of 0.5–1.5 wt% CP on rebar corrosion was assessed via an accelerated corrosion test. The macrocell current, half-cell potential measurements (HCP), reinforcement cover crack propagation, and rebar deterioration were monitored. The resistance of mortar specimens to acid-induced degradation was also evaluated over time. The corrosion test results indicate that steel rebar corrosion initiation in the mortar expedited as the CP dosage in mixtures increased. Consequently, the time required for the CP-modified specimens to crack shortened. Moreover, non-uniform rebar section loss and surface crack width widening were also observed in CP-modified mortar specimens. However, X-ray diffraction (XRD) analyses of the plain Ref and 1.5% CP corrosion byproduct residues indicated that key phases such as akaganeite, goethite, lepidocrocite, hematite, and magnetite were quantitatively similar. Interestingly, the addition of 1.0–1.5% CP to mixtures enhanced the acid attack resistance of mortars. For now, these results indicate that CP should only be used as a chemical admixture in unreinforced cement composites.

Durability assessment of Self-Curing high performance concretes containing zeolite admixture

The infrastructural development activities are accompanied with construction of various facilities to provide safe and sustainable livelihood to the society. Concrete being one of the most extensively used construction material, there has been a growing demand in terms of consumption of cement fine aggregate, coarse aggregate and water. There have been numerous attempts to utilize alternate binding materials as a partial replacement of cement. Scarcity in aggregates are also being addressed through alternate filler materials like manufactured sand or artificial aggregates. Water scarcity in many locations has been forcing the researchers to look for alternate methods of curing either through addition of self-curing compounds or through coatings which doesn’t permit the internal water to evaporate. There have been numerous attempts to quantify the functioning characteristics of the selfcuring mortars and self-curing concretes. However, the research on zeolite as admixture in self-curing concrete have not been addressed to a great extent. The current work was focused to study the durability aspects of self-curing concretes containing calcined zeolite and uncalcined zeolite as a partial replacement of cement. A relative comparison of performance characteristics of air cured self-curing concretes with conventional concrete cured in water have been presented. Also, attempts were made to evaluate the corrosion characteristics of embedded reinforcement through half-cell potential measurements. The extensive study on these proposed concretes revealed the fact, that it is possible to develop high strength concretes without conventional curing practices. However, these concretes had superior durability characteristics which was witnessed through resistivity, rapid chloride penetration test (rcpt) and cyclic wet and dry test.

Effect of admixed chloride and molarity of NaOH solution on early-age strength and reinforcement corrosion in FA/GGBS geopolymer concrete

Chloride persuaded steel reinforcement corrosion is an important durability issue in concrete structures. In this present study, the corrosion of reinforcing steel was evaluated in 0% and 3% sodium chloride admixed fly ash (FA)/ground granulated blast furnace slag (GGBS) GPC mixes. Two different molarities of NaOH solution i.e. 8 M and 10 M were used for preparing the GPC mixes with FA/GGBS proportions of 100/0 (wt.%), and 70/30 (wt.%). Reinforced geopolymer concrete prismatic specimens were prepared for half-cell potential and linear polarization resistance (i.e. LPR) measurements after 28 days and 180 days of its manufacturing. The obtained results showed that the early age 7 days compressive strength of GPC mixtures reduced with the existence of NaCl. The higher value of compressive strength was detected in GPC prepared with FA/GGBS proportion of 70/30 as compared to that made with FA/GGBS proportion of 100/0. Further, GPC made with higher molarity (10 M) of NaOH solution showed greater strength than that made with lower molarity (8 M) of NaOH solution. The less negative half-cell potential value and lower corrosion current density (Icorr) value of steel reinforcement in GPC was observed at the later age i.e., at 180 days in all GPC mixes as compared to 28 days. The higher chance of rate of corrosion, and the higher Icorr of steel reinforcement was detected in 3.0% NaCl added geopolymer concrete. Further, more negative half-cell potential and higher Icorr of steel reinforcement were detected with a rise in molarity of NaOH solution in GPC made with FA/GGBS proportion of 70/30 at both ages (i.e. at 28 days and 180 days). However, mostly less negative half-cell potential and lower Icorr of reinforcing steel were detected with a rise in molarity of NaOH solution in GPC made with FA/GGBS proportion of 100/0 at both ages.