Effect Of Electrochemical Chloride Extraction Research Articles

Effect of ECE in removing chlorides at free and bound ones in concrete contaminated with chlorides in cast and with penetrated chlorides

The present study concerned the effect of electrochemical chloride extraction (ECE) to chloride-contaminated concrete on chloride removal with incremental depths after the ECE at 1000 mA/m2 for 2, 4 and 8 weeks. The steel reinforcement was taken as an anode, while the titanium mesh as cathode. The chloride was extracted by diluting concrete dust sample in acid solution and still water for total and free chlorides, respectively. As a result, most free chlorides were removed from concrete at the increased current density, while bound chlorides were quite removed, presumably due to a reduction of the alkalinity of concrete.

Effects of Electrochemical Chloride Extraction on the Properties of Chloride-Contaminated Reinforced Concrete by Using Magnesium Phosphate Cement Bonding Carbon Fiber Reinforced Plastics as Anode

Effects of Electrochemical Chloride Extraction on the Properties of Chloride-Contaminated Reinforced Concrete by Using Magnesium Phosphate Cement Bonding Carbon Fiber Reinforced Plastics as Anode

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.

Improvement on the Repair Effect of Electrochemical Chloride Extraction Using a Modified Electrode Configuration.

To improve the repair effect of electrochemical chloride extraction, a modified electrode configuration is applied in this investigation. In this configuration, two auxiliary electrodes placed in the anodic and cathodic electrolytes were used as the anode and cathode, respectively. Besides this, the steel in the mortar was grounded to protect it from corrosion. By a comparative experiment, the potential evolution, various ions concentrations (Cl−, OH−, Na+, and K+) in different mortar depths, the corrosion potential, and the current density of the steel were measured. The results indicate that compared to electrochemical chloride extraction with the traditional electrode configuration, this electrochemical chloride extraction method with a modified electrode configuration has a similar chloride removal ratio. Besides this, potential of steel is just about 800 mV for a saturated calomel electrode (SCE) during the treatment, which did not reach the hydrogen evolution potential. The phenomenon of the accumulation of OH−, Na+, and K+ did not occur when the modified electrode configuration is applied. Additionally, higher corrosion potentials and lower corrosion current rates were measured after performing electrochemical chloride extraction with the modified electrode configuration. Additionally, it is a short period of time for the steel to go from activation to passivation. On this basis, the modified electrode configuration may overcome the drawbacks of electrochemical chloride extraction.

The Effects of Electro-Chemical Chloride Extraction on the Migration of Ions and the Corrosion State of Embedded Steel in Reinforced Concrete

The effects of electrochemical chloride extraction were evaluated using different electrolytes and binders on cylindrical concrete specimens with a water/binder ratio of 0.4. Two-percent NaCl by weight of binder was added to the water as a chloride source during concrete casting. After the specimens were immersed in water for three months, direct current 0.5 A/m2 was applied to release approximately 30% initial chloride. The use of intermittent mode during extraction process was more efficient in releasing chloride than a continuous mode. After treatment, although the average remaining-chloride content was higher than threshold value, its content at the interface was only approximately 0.4%. The accumulation of alkaline ions around the embedded steel was noticeable but the distribution of calcium ions showed as different tendency. The migration of ions from the electrolyte was insignificant. This demonstrated the important role of internal ions in transferring the charge during extraction; simultaneously, the decomposition or transformation of hydrated products is inevitable. After the treatment was stopped for four weeks, the half-cell potential of the steel reached to low-corrosion state.

Effects of Electrochemical Chloride Extraction on Hydrated Products of Various Cement Paste Systems

Effects of Electrochemical Chloride Extraction on Hydrated Products of Various Cement Paste Systems

Shape Effect of Electrochemical Chloride Extraction in Structural Reinforced Concrete Elements Using a New Cement-Based Anodic System

This article shows the research carried out by the authors focused on how the shape of structural reinforced concrete elements treated with electrochemical chloride extraction can affect the efficiency of this process. Assuming the current use of different anode systems, the present study considers the comparison of results between conventional anodes based on Ti-RuO2 wire mesh and a cement-based anodic system such as a paste of graphite-cement. Reinforced concrete elements of a meter length were molded to serve as laboratory specimens, to closely represent authentic structural supports, with circular and rectangular sections. Results confirm almost equal performances for both types of anode systems when electrochemical chloride extraction is applied to isotropic structural elements. In the case of anisotropic ones, such as rectangular sections with no uniformly distributed rebar, differences in electrical flow density were detected during the treatment. Those differences were more extreme for Ti-RuO2 mesh anode system. This particular shape effect is evidenced by obtaining the efficiencies of electrochemical chloride extraction in different points of specimens.

Effect of Electrochemical Chloride Extraction on the Bond Performance between Steel Bar and Concrete

Based on beam specimens of 100mm×100mm×400mm, the effect of electrochemical chloride extraction (ECE) on bond performance between steel bar and concrete contaminated by chloride was studied by determining the bond strength of them. During the test, 1%, 2% and 3% NaCl by weight of cement were mixed into concrete to simulate chloride contamination. In the process of ECE, four kinds of current density (1, 2, 3, 5 A/m2of steel bar area) and electric quantity (500, 1000, 1500 and 3000 A.h/m2of steel bar area) were taken into account, respectively. It is indicated that the bond strength between steel bar and concrete was degraded after ECE treatment, the more the current and the electric quantity of ECE are, the more the loss of bond strength is, and the initial content of chloride in concrete has a little influence on the bond strength.

Degradation of bond between steel bar and freeze-thaw concrete after electrochemical chloride extraction

The effect of electrochemical chloride extraction (ECE) on bond strength between steel bar and freeze-thaw concrete contaminated by chloride was experimentally investigated for beam specimens with dimensions of 100 mm×100 mm×400 mm. During the experiment, 3% NaCl (vs mass of cement, mass fraction) was mixed into concrete to simulate chloride contamination, and the specimens experienced 0, 25, 50, 75 freeze-thaw cycles before ECE. In the process of ECE, different current densities and durations were adopted. It is indicated that the bond strength between reinforcement and concrete decreases with the increase of freeze-thaw cycles; the more the current and the electric quantity of ECE are, the more the loss of bond strength is; and the largest loss is up to 58.7%. So, it is important to choose proper parameters of ECE for the reinforced concrete structures contaminated by chloride and subjected to freeze-thaw cycles.

Evaluation of the short and long-term efficiencies of electro-chemical chloride extraction

The short and long-term effects of electro-chemical chloride extraction (ECE) treatment on corrosion rate of corroded reinforcement have been studied. The factors controlling ECE treatment were identified, and the alterations which occurred in the chloride profile of the cover zone due to ECE process were followed. Contaminated reinforced OPC and SRC mortar specimens made with 1 or 2% NaCl, by mass of cement, were prepared, cured and then subjected to 3 or 5% NaCl for one year. These specimens were finally treated with ECE using various impressed current densities (1 and 2 A/m 2) and electrolytes (water and calcium hydroxide) for 2, 4 and 8 weeks. The state of corrosion was monitored regularly every 2 weeks from halting ECE process up to 52 weeks using zero-resistance ammeter device for measuring the corrosion current density of reinforcement. Selected samples from the cover zone of the untreated and treated specimens were finally taken to assess their chloride profiles.

Effect of Electrochemical Chloride Extraction on the Steel Reinforced Concrete

Electrochemical chloride extraction (ECE) is used for the rehabilitation of chloride-contaminated concrete. High current densities of steel surface are applied between the steel and a temporary external anode which is placed on the concrete surface. Anions are pushed away from the cathode (steel reinforcement), and cations are accumulated at the cathode. In this study chloride ions were found in the electrolyte during ECE. The extraction efficiency of chlorides was obvious. After treatment, the amount of chlorides around the reinforcement was greatly reduced. ECE had insignificant effect on the compressive strength. Steel potentials in treated specimens showed a strong shift towards more positive values, while potentials in control specimens remained strongly negative.

The effect of electrochemical chloride extraction on pre-stressed concrete

Chloride induced corrosion is the main cause of corrosion in reinforced concrete structures. Electrochemical chloride extraction, also known as desalination, is applied to concrete structures containing ordinary reinforcement in order to extract chlorides from the concrete. During this process, atomic hydrogen generated on the steel surface can cause hydrogen embrittlement of the steel. High strength steels, such as those that are used in pre-stressed concrete, are particularly susceptible to hydrogen embrittlement which, at worst, can result in the sudden and unpredictable collapse of a structure. This paper presents the results of a series of constant extension rate tests conducted on 22 pre-stressed concrete specimens that had been subjected to electrochemical chloride extraction. The paper concludes that the risk of hydrogen induced brittle fracture due to electrochemical chloride extraction cannot be altered with modification of the treatment parameters, such as current density or treatment duration. It was also uninfluenced by different surface states of the steel (corroded or not corroded). Therefore, based on the findings of this study, it can be concluded that electrochemical chloride extraction should not be applied to pre-stressed concrete.

Influence of electrochemical chloride extraction on the bond between steel and concrete

Laboratory tests were undertaken to assess the effect of electrochemical chloride extraction (ECE) on the bond strength of plain reinforcing steel in concrete. Specimens were cured/stored for 3 months prior to ECE and were then treated at a current density of between 0·02 and 0·75 A/m2 of reinforcement area for periods of up to 32 weeks. Chloride-free specimens showed a small gradual increase in bond strength after ECE. Prior to ECE, specimens containing chloride (1·5% by weight of cement) had higher bond strength than chloride-free specimens, due to corrosion. This enhanced bond strength was largely eliminated by 2 weeks of ECE, due to dissolution of corrosion products, although these specimens also then showed a slight increase in bond strength after further treatment. Tests carried out 10 min, 24 h and 28 days after ECE suggest that bond strength reduces during ECE. Variations in bond strength are considered with regard to the processes occurring during ECE, and the practical implications of these findings are discussed.

The effect of the electrochemical chloride extraction treatment on steel-reinforced mortar Part I: Electrochemical measurements

A study has been made of the effectiveness of electrochemical chloride extraction in reducing chloride-induced corrosion of rebar embedded in steel with chlorides added with the mixing water, ingressed by ponding with a NaCl solution, or both. After exposure for 1 year, specimens with and without chlorides were subjected to an electrochemical chloride extraction treatment. Corrosion measurements taken before and after extraction showed that the treatment halted chloride-induced pitting in those specimens that were under attack. However, the extraction treatment increased the overall corrosion rate for all specimens studied due to reduction of the passive film and significant changes in pore solution and cement chemistry adjacent to the rebar.

Effect of Electrochemical Chloride Extraction on Concrete Properties: Investigation of Field Concrete

An investigation to determine the suitability of electrochemical chloride extraction (ECE, also known as desalination) for the reinforced concrete substructure on a bridge in the north of England is reported. Part of a cross head was removed during demolition. After ECE treatment by the proprietary Norcure technique, cores were taken from the treated area. Representative cores were then taken from adjacent cross heads and subjected to a series of laboratory tests and examinations. These tests revealed that the treatment increased the concrete’s ability to resist the ingress of water, oxygen, and ions. This should make the concrete more durable and more resistant to future chloride ingress and corrosion.

Effects of electrochemical chloride extraction on chemical and mechanical properties of hydrated cement paste

To simulate the effects of applying electrochemical chloride extraction to reinforced concrete, rectangular prism specimens of hydrated cement paste containing sodium chloride were subjected to electrolysis between centrally embedded steel cathodes and external anodes of activated titanium. The cathodic current density was galvanostatically controlled at values in the range 1-5 A/m2 for periods of 4-12 weeks. Control specimens in which the steel was subjected to a modest level of cathodic protection at a current density of 5 mA/m2 were also prepared. After treatment, the specimens were sectioned and analysed to determine changes in the distribution of ions within the pore solution phase and in the total chloride content. Microhardness profiles were also measured. It was found that, as well as causing the free and bound chloride content of the specimens to decrease with time, the higher current densities also produced major increases in the pore solution alkali concentrations near the embedded steel. Associated with this local increase in pH value, there was an increase in soluble sulphate ion concentration which appeared to be controlled by solubility equilibria. For the limited range of specimens studied, no significant changes in microhardness profiles were observed.