Electrochemical Chloride Extraction Research Articles

Monitoring by electrochemical impedance spectroscopy of mortars subjected to ingress and extraction of chloride ions

Reinforcement corrosion is usually detected at advanced ages. Electrochemical analyses have been found to be efficient for the detection of corrosion phenomena at early age. This study sought to evaluate the use of electrochemical impedance spectroscopy (EIS) for the characterization of evidence of corrosion. For this purpose, reinforced mortar specimens were monitored, initially during exposure in a salt fog chamber for 150 days and subsequently during electrochemical chloride extraction. During these steps, complementary tests were performed to explain the results (scanning electron microscopy, chloride depth determination, corrosion potentials and chromatography of chloride ions). The results indicated that the EIS can identify important moments of chloride penetration in cementitious materials, such as the hydration of the material, the arrival of chloride ions in the reinforcement region, the depassivation period of the steel, the beginning of the corrosion process in the rebar and the monitoring of the chloride exit over time.

Experimental investigation on seismic behavior of corroded RC columns under artificial climate environment and electrochemical chloride extraction: A comparative study

Corrosion of reinforcement bars can cause reinforced concrete (RC) columns more vulnerable under seismic loads. In this study, the seismic behavior of corroded RC columns was experimentally studied with a focus on the comparison between two different accelerated corrosion techniques by using artificial climate environment (ACE) and electrochemical chloride extraction (ECE). To do this, six RC square columns were designed and fabricated as the test specimens. The test specimens were categorized into two groups with a low level and a high level of axial compression ratio (i.e., 0.1 and 0.45), respectively, and each group includes three test specimens, i.e., an uncorroded column and two corroded columns under ACE and ECE techniques. An X-ray diffraction approach was used to examine the major ingredients of corrosion products attached on the corroded reinforcement bars under ACE and ECE techniques. The column specimens were subjected to repeated cyclic loadings, and the failure modes, hysteresis and backbone curves, stiffness degradation, ductility level and energy dissipation of the specimens corroded under different techniques were compared. The results show that, under a consistent target corrosion level, the ECE corrosion technique can cause more significant damage to the corroded RC columns than the ACE corrosion technique, leading to a change of failure mode and worse hysteretic performance.

Effect of Imidazoline Inhibitor on the Rehabilitation of Reinforced Concrete with Electromigration Method.

Steel bars embedded in reinforced concrete are vulnerable to corrosion in high chloride environments. Bidirectional electromigration rehabilitation (BIEM) is a novel method to enhance the durability of reinforced concrete by extracting chloride out of concrete and introducing an inhibitor to the surface of the steel bar under the action of an electric field. During the migration process, a higher ionization capacity of the inhibitor with a symmetrical molecular structure was introduced. A new imidazoline inhibitor was, therefore, employed in this study due to its great ionization capacity. The effect of imidazoline and triethylenetetramine inhibitor on chloride migration, corrosion potential, and strength of concrete were explored. The research results showed that the effect of chloride extraction and electrochemical chloride extraction made no significant difference on the surface of the concrete, where chloride extraction efficiency was more than 70%, and the chloride extraction efficiency was more than 90% around the location of the steel. while a dry-wet cycle test, the potential of concrete increased by about 200 mV by mixing imidazoline inhibitor. The imidazoline inhibitor was found to be effective at facilitating chloride migration and ameliorating corrosion, meanwhile, it had a negligible impact on the concrete’s strength.

Study on the potential change of corroded reinforced concrete in ECE with MPC-CFRP as anode

Aiming at the rust removal requirements of reinforced concrete, the MPC-CFRP composite material was used as the external anode, and the Electrochemical chloride extraction (ECE) method was used to test the polarization curve of the steel bar under different ECE current densities, and the potential changes of the steel bar at different times were analyzed. The results show that the ECE system with MPC-CFRP as the external anode has a good effect of reducing the corrosion rate and the risk of corrosion of steel bars. The current density of 3A/m2is higher than that of 1A/m2in dechlorination efficiency. After 28 days of ECE, the current density of 1A/m2and 3A/m2can re passivate the reinforcement.

Efficiency of Different Electrolytes on Electrochemical Chloride Extraction to Recover Concrete Structures under Chloride‐Induced Corrosion

Chloride‐induced corrosion is one of the main causes of concrete deterioration and imposes a challenge to sustainability. Traditional techniques to repair corroded structures consisted of basically removing the damaged area, which was either economical or sustainable. Therefore, electrochemical chloride extraction (ECE) gained popularity for being an efficient nondestructive treatment applied temporarily to structures. On this line, this manuscript aims to raise the efficiency of ECE by an optimal decision of the treatment setup concerning the electrolyte choice. Three different electrolytes were tested, namely, tap water, calcium hydroxide, and lithium borate. Experimental results pointed to lithium borate as the most efficient electrolyte for extracting chlorides while calcium hydroxide was a better choice to repassivate the structure and even heal cracks, due to a possible electrodeposition of the electrolyte ions on the cement matrix. Thus, depending on the main goal of the treatment, different electrolytes achieve a better performance, which highlights the importance of pretreatment evaluation to see in which stage of corrosion damage is the structure.

Deterioration of static mechanical properties of RC beams due to bond damage induced by electrochemical rehabilitation

Electrochemical rehabilitation (ER) techniques are very efficient and non-destructive methods to improve the durability of existing concrete structures. However, the induced bond damage between steel bar and concrete will affect the mechanical properties. In order to investigate the effect of ER on the static mechanical properties of concrete structures, three types of tests after electrochemical chloride extraction and bidirectional electromigration were carried out in this study. Based on the desired constitutive models, finite element analysis was then used to verify the effect of bond damage on the static mechanical properties of RC beams. Results showed that the spacing and width of cracks both increased with increasing current density and duration. The yield bearing capacity of beams decreased by 20% when the electrical parameters were 3 A/m2 for 4 weeks and 5 A/m2 for 2 weeks. Careful investigation with experiments, finite element simulations, and theoretical explanation demonstrated that bond damage was the main reason. As a result, a modified flexural stiffness model of concrete beams considering the electrification parameters was established. Combined with data from the relevant literature, the optimal quantity of electric charge for ER balancing chlorine removal efficiency and flexural stiffness was finally determined as 500–1400 Ah/m2.

Corrosion assessment and control techniques for reinforced concrete structures: a review

Steel corrosion is the main source of damage and early failure of reinforcement concrete structures that in turns create huge economical loss and creating environmental problems. In the past, several corrosion assessment techniques such as potential measurement, gravimetric weight loss measurement, electrical resistivity measurement, sensors and electrochemical methods for instance potentiodynamic polarization, linear polarization resistance, galvanostatic pulse, and electrochemical impedance have been developed to detect corrosion condition of steel in concrete. Though the potential measurement, resistivity measurement and sensors can only provide the qualitative information about the steel corrosion. The weight loss measurement is an efficient technique for corrosion rate measurement of steel, but it is destructive and requires long exposure times. The electrochemical techniques are non-destructive in nature and are used to determine corrosion rate of steel in laboratory as well as field studies. However each of these methods possesses certain advantages and limitations, therefore a combination of these techniques is recommended to use to obtain the corrosion condition of steel. As far as corrosion control techniques for steel reinforced concrete are concerned, several methods such as cathodic protection, electrochemical chloride extraction, surface treatments of the steel, surface treatment of concrete, utilization of mineral admixtures and chemical corrosion inhibitors have been developed in the past. Each of these methods offers some advantages and disadvantages. Thus, more researches are required to develop such methods of corrosion protection of steel that are economical, durable, environment-friendly and do not cause any adverse effect on the structural performance of concrete and steel.

Effects of electrochemical chloride extraction on the bonding properties of corroded reinforced concrete by the anode of magnesium phosphate cement bonding carbon fiber-reinforced plastics (CFRP)

This paper studied the effects of electrochemical chloride extraction (ECE) on the bonding properties of corroded reinforced concrete with the anode of Magnesium phosphate cement (MPC) bond CFRP. The results indicated that ECE can efficiently remove the chloride ions in the concrete. The interfacial bonding properties of steel-concrete decreased with the increase of chloride removal current density. Proper corrosion ratio of steel bars can reduce the bonding strength loss caused by ECE treatment.

Electrochemical chloride extraction to repair combined carbonated and chloride contaminated reinforced concrete

The increasing international interest in contemporary architecture has drawn attention to the numerous listed buildings made of reinforced concrete in Europe, and especially in France. The main source of deterioration of this cultural heritage is the corrosion of rebars through carbonation or chloride contamination, but also often by a combination of both. The present study explored this combined corrosion mechanism in reinforced concretes, and investigated Electrochemical Chloride Extraction (ECE) as a technique to stop or decrease corrosion. The analytical approach was based on physico-chemistry, electrochemical measurements, Raman spectroscopy and SEM examinations. The results evidenced the aggressiveness of the combined carbonation and chloride-induced corrosion, and demonstrated the efficiency of the ECE treatment in terms of chloride extraction and reduction of corrosion rate. It appears that ECE treatment only reduces corrosion activity by increasing pH to a value of 10. Nevertheless, the long term durability of the treatment is questionable as the return to a sound concrete passivity is not obtained.

Hydrogen embrittlement risk control of prestressed tendons during electrochemical rehabilitation based on bidirectional electro-migration

Abstract Bidirectional electro-migration rehabilitation (BIEM) is type of electrochemical rehabilitation that allows for simultaneous chloride ion removal and inhibitor injection into the steel bar surface. The inhibitor migrates across the surface of the steel bar, altering its pH and forming a thin layer of isolation that reduces hydrogen evolution. In this paper, sensitivity of hydrogen embrittlement was studied using constant strain rate tensile analysis, fracture energy ratio, and fracture morphology. When compared with electrochemical chloride extraction (ECE), BIEM treatment enhanced the critical current density and reduced the stripes number in radical zone. The fracture energy ratio remained at a high level, even with a current density and BIEM treatment time that were no more than 3 A/m2 and 14 d respectively. The results indicated that the sensitivity of prestressed tendons to hydrogen embrittlement after BIEM was markedly lower than that after ECE. Collectively, these results indicate that BIEM treatment can mitigate the application limitations of the current electrochemical rehabilitation technology used on prestressed concrete structures.

Numerical analysis on efficiency of electrochemical chloride extraction of one side anode in concrete

Electrochemical Chloride Extraction (ECE) is one of the key ways to enhance the durability of concrete structure which suffered or are suffering from chloride attack. To deeply understand the influence of various factors on chlorine removal efficiency, this paper presents a numerical study to characterize transport and distribution of each ion during ECE. A plain concrete specimen was used as an example to investigate the influence of various factors on the efficiency of ECE of one side anode. These factors were: time, current density, ratio of cover thickness and side length, initial chloride ion concentration, and ratio of cross-sectional area of reinforcement to cross-sectional area of specimen. In addition, the quantitative relationship model between these factors and total electrochemical desalination efficiency are also proposed. Good agreement between the present the quantitative relationship model of total desalination efficiency and the FEM solution illustrates reliability and accuracy of the proposed relationship model.

Role of cement type on performance change of reinforcing steel due to chloride extraction

Abstract Electrochemical chloride extraction “ECE” has been used for reinforced concrete structures to protect steel from chloride-induced corrosion. ECE may change the performance of steel interface as represented by polarization resistance, corrosion rate and pull out bond strength. Thus, there is a need to evaluate these effects before and after ECE treatment for reinforced concrete made with different types of cements. This paper presents the evaluation of the performance changes of concrete specimens containing steel rebar with different times of (ECE) treatments. In this study; plain and blended cement which are commonly used in marine environment are investigated; two types of ordinary Portland cement “CEM I 42.5N” with different alkalis and percentages of C3A and two types of blended cement; SLAG cement “CEMII/B-S-42.5N” and CEM I 42.5N with 10% silica fume. Concrete mixes are subjected to either internal or external sources of chlorides. Other protective methods have been evaluated for comparison; corrosion inhibitor admixtures and cementitious surface coating. Corrosion initiation and corrosion rate were estimated by non-destructive techniques (Half-cell potential and polarization resistance), while the pull out bond strength was evaluated for all mixes before and after chloride extraction. The results indicated that applied ECE is an effective method of chloride removal, but it adversely affects the pull out bond strength irrespective of cements type. However, the use of silica fume blended cement has been proved to be effective.

Study on the variation of electric potential in reinforced concrete members during accelerated corrosion and electrochemical chloride extraction process

This paper mainly studies the corrosion potential and current of reinforced concrete beams during accelerated corrosion and electrochemical chloride extraction. The results show that the corrosion potential and current of concrete beams increase with the corrosion time. In the process of electrochemical chloride extraction, the corrosion potential and current of concrete beams decrease with the prolongation of chlorine removal time. Electrochemical chloride extraction can effectively reduce the corrosion rate of reinforced concrete components and reduce the corrosion risk of steel bars.

Experimental Study on Reinforcement and Chloride Extraction of Concrete Column with MPC-CFRP Composite Anode

In this research, Magnesium Phosphate Cement (MPC) was innovatively used to bond with Carbon Fiber Reinforced Plastic (CFRP) in order to form the MPC-CFRP as a composite material, adopted both for chloride ions extraction and reinforcement of concrete columns. First of all, a series of tests were conducted to evaluate the feasibility of the MPC-CFRP as anode of Electrochemical Chloride Extraction (ECE) system, including chloride ions concentration, Scanning Electron Microscope (SEM) and tensile strength. Then, the MPC-CFRP was used to wrap around reinforced concrete column for the sake of reinforcement and extraction of chloride ions. The test results indicated that the chloride extraction efficiency and the tensile resistance of the MPC-CFRP electrode were superior to the control group. The ECE process can decrease the interface bonding strength between the concrete and the steel rebar while the compression resistance of the columns could be increased remarkably. Therefore, the MPCCFRP composite material is capable of achieving the dual functions of strengthening and repairing the reinforced concrete construction.

Instant performance verification after electrochemical chloride extraction by enhanced corrosion testing

Electrochemical chloride extraction (ECE) is meant to re-establish the corrosion protection of concrete for the embedded reinforcement by removing chloride non-destructively and by enhancing the alkalinity of the rebar surrounding concrete. Both effects depend on various parameters, such as concrete cover, rebar spacing, chloride profile (especially if chloride ingress is deeper than the outside rebar layer) and concrete permeability. Often these parameters require long or multi-stage treatments, which basically can achieve any desired target level of chloride profile and impressed charge, but become a costly solution after a while. The acceptance criteria mentioned in CEN TS 14038-2 clause 8.6 refer to the achieved chloride content and to the amount of impressed charge, which are the conventional, easy measurable, but not direct parameters for evaluating the corrosion activity. A third parameter – the re-measurement of potentials for assessing (intended) low potential gradients and more positive average potentials – requires some weeks to months of depolarization and evaporation of water, before such a measurement can be applied successfully. A promising approach for an instant performance testing after an ECE treatment has been made on several occasions with follow-up measurements of electrolyte resistance, polarization resistance and corrosion current. Convincing changes towards significantly lower corrosion activity could be obtained (and compared to known classified values) – regardless of sometimes high residual chloride and very wet concrete. These data could be verified when re-assessed after some weeks, so enhanced corrosion measurements seem to be a useful tool for either establishing that the designed treatment time has been sufficient or to check on possible earlier termination of the treatment during a running ECE.

A study on the deterioration of interfacial bonding properties of chloride-contaminated reinforced concrete after electrochemical chloride extraction treatment

This paper adopted magnesium phosphate cement (MPC) bonding CFRP (MPC-CFRP) as anode materials and the effects of ions distribution, interfacial composition and microstructure on the deterioration of interfacial bonding properties of chloride-contaminated reinforced concrete after electrochemical chloride extraction (ECE) treatment were systemically studied. The results showed that MPC-CFRP materials can be used as the ECE anode and achieve the chloride removal of concrete. Current density is the main influence factor for ECE treatment, the influence of temperature on ECE is small. ECE treatment could effectively remove the chloride ions and decrease the corrosion risk of rebar in concrete. However, ECE treatment altered the interfacial composition and microstructure. After ECE treatment, the contents of K+, Na+ and OH− around the rebar increased significantly, new alkali metal ions rich cementitious phase and directional arrangement of lamellar hydration product with high Ca/Si ratio were formed. Besides, ECE treatment caused the cracking and decomposition of C-S-H in rebar-concrete interface. As a result, the interfacial bond strength decreased. Taking all these factors into consideration, the relatively better condition for ECE treatment is 2 A/m2.

Application of combined electrochemical treatments to reinforced concrete: Electrochemical chloride extraction plus cathodic protection

It has been studied the possibility of using a graphite–cement paste anode for combined treatments of electrochemical chloride extraction plus cathodic protection on reinforced concrete elements. These treatments would be interesting in cases of structures heavily contaminated with chlorides and continuously exposed to a harsh chloride environment. It has been shown that, in the experimental conditions of this work, the anode is not damaged during the electrochemical chloride extraction step. The application of a previous chloride extraction step allows working with a lower current density at the cathodic protection step, which reduces the risk of damages of the anodic system. A chloride barrier effect parameter has been defined, based on the reduction of the chloride uptake by concrete, due to cathodic protection action, referred to the chloride uptake of the reference (not treated) specimens. The values of the chloride barrier effect parameter found in this work are about 20%.

Electrochemical chloride extraction (ECE) based on the high performance conductive cement-based composite anode

The chloride ions, imbibition in the reinforcement concrete, are detrimental to the durability of the material. In this paper, a low shrinkage and high ductile conductive cement-based mortar was developed as a novel external anode for electrochemical chloride extraction (ECE). The electricity resistivity, fracture energy and drying shrinkage of mortar with different length, volume fraction of carbon fiber were investigated to optimize mix proportion of conductive cement base mortar (CCM). Subsequently, the proposed CCM with good performance was then utilized as the anode to remove the chloride ions electrochemically from three types of reinforced concrete. The chloride ions distribution in concrete and CCM anode were obtained to evaluate the electrochemical chloride extraction (ECE) efficiency. Additionally, the microstructures, elements distribution and calcium hydroxide content of CCM anode and ITZ were achieved for the further mechanism investigation. Experimental results indicated that the ECE efficiency for CCM anode was as high as that of traditional stainless mesh anode. The CCM anode with 0.8% volume fraction of carbon fiber exhibits excellent ductile and conductivity performance. Furthermore, CCM anode thickness influences significantly on the chloride removal efficiency and residual chloride proportion in concrete and CCM anode. And 10 mm thickness of CCM anode was a suitable value to ECE treatment of reinforced concrete. The microstructure and calcium hydroxide content in CCM anode showed no degradation after 35 days of ECE treatment, which indicated that the CCM anode have an excellent cracking resistance capacity and could be re-used.

Performance of carbon fiber added to anodes of conductive cement-graphite pastes used in electrochemical chloride extraction in concretes

Performance of carbon fiber added to anodes of conductive cement-graphite pastes used in electrochemical chloride extraction in concretes

Effect of ultrasound on electrochemical chloride extraction from mortar

In this paper, the effect of auxiliary ultrasound on electrochemical chloride extraction (ECE) was studied. The chloride removal efficiency was investigated by examining the chloride content with ultrasound-assisted ECE and changing the introducing time of ultrasound. The experimental results showed that removal of chloride ions was noted to be more effective in ECE treatment assisted with ultrasound treatment (UT). In addition, the lower w/c ratio led to more distinct effect of ultrasonic cavitation on chloride removal. Electrochemical behaviors measured with different treatment revealed that UT treatment was effective on moderating the corrosion condition. Microstructural analyses revealed a significant alteration in composition and morphology of cementitious phases with UT treatment. Pull-out tests indicated that ultrasound had a certain negative impact on the bond strength. Although the effect of introducing ultrasound in the first 2 weeks or the last 2 weeks on the extraction efficiency was not obvious, intermittent ultrasound could not only ensure the chloride extraction efficiency, but also reduce the adverse effect of ultrasound on the bond strength.