Papers by Keyword: Electrochemical Chloride Extraction

Abstract: This paper examines the impact of type of electrolyte solutions, standing time without electricity on the reinforced bond of the concrete of different water cement ratio before and after chloride extraction, processes the microscopic structure and mechanism analysis. The electrochemistry method can discharge the chlorine salt without destroying the original concrete protective layer and realize the non-loss, low cost and fast repair for the concrete structure destroyed by the chlorine salt corrosion. The results show a substantial loss of the reinforced bond (70-76%) after chloride extraction according to the concrete of different water cement ratio, and the decrease is in proportion to the current-on time and the electrochemical capacity of the electrolyte. The increased partial porosity of the cathode area of the concrete by the chlorine and hydrogen produced in the process of electrochemical chlorine extraction, the decomposition and softening of the concrete hydration products with external field are the main reasons for the dramatic drop of the reinforce bond.

Abstract: Electrochemical chloride extraction – ECE is an effective method to rehabilitate reinforced concrete structure, which has been corroded. This study investigated concentration of chloride remained in concrete and half-cell potential of the steel reinforcement after ECE using interrupting period of electricity current. Efficiency of ECE using Ca (OH)₂ was surveyed with two current density of 0.5 and 1A/m². In this study, ECE treatment was proceeded intermittently in approximately 8 weeks. Results pointed out that chloride concentration decreased to 30 – 60% significantly, especially at in the vicinity of reinforcing steel. Simultaneously, half-cell potential of the steel reinforcement after 4 weeks halted treatment stabilizes in low-corrosion rate.

Abstract: This paper presents the first use of ultrasound technique during electrochemical chloride extraction (ECE). The effect of ultrasound on the extraction efficiency was studied, and the mechanism of ultrasound in improving the extraction efficiency was also discussed in this paper. Testing results showed that ultrasound was conducive to enhance the efficiency of chloride removal to a certain extent, especially in the first 3 weeks. Ultimately, compared with ECE treatment, the chloride removal efficiency of ultrasonic-assisted ECE nearly increased 10%. In addition, the corrosion potentials measured 2 months after treatment indicated the effectiveness of ultrasonic-assisted ECE in protecting eroded rebars from further corrosion.

Abstract: A creative methodology of ultrasonic-electrochemical chloride extraction (UT) is proposed which is an improvement of the traditional electrochemical chloride extraction (ECE) through the assistant of ultrasonic wave and according experimental investigation on the viability of this method is carried out. The results indicated that the Cl- extraction efficiency of UT was approximately 19% higher than that of ECE, and the corrosion current density of UT group obtained through Linear Sweep Voltammetry was also the lowest which further demonstrates that ultrasonic wave had positive and obvious effect on halting the corrosion of Cl- on steels.

Abstract: Electrochemical Chloride Extraction (ECE) is a new method to halt the corrosion of steel in concrete contaminated by chloride. The bond strength between steel and concrete with and without ECE were tested through steel pull-out test, and the effects of current density and total charge passed during ECE on it were analyzed. A demo device was designed to analyze the hydrogen evolution during ECE by dividing the cathode reactions and anode reactions into two sealed bottles. The relation between hydrogen content and electrons passed in the circuit and the adverse effects of the hydrogen on steel reinforced concrete was conducted. Through drilling appropriate number of holes from concrete surface into the steel, some hydrogen can be released and its adverse effects can be mitigated in a certain degree.

Abstract: 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/m² of steel bar area) and electric quantity (500, 1000, 1500 and 3000 A.h/m² of 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.

Abstract: 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.