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.

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The Compressive Strength and Resistivity toward Corrosion Attacks by Chloride Ion of Concrete Containing Type I Cement and Calcium Stearate

International Journal of Corrosion ◽

10.1155/2018/2042510 ◽

2018 ◽

Vol 2018 ◽

pp. 1-9

Author(s):

Agus Maryoto ◽

Buntara Sthenly Gan ◽

Nor Intang Setyo Hermanto ◽

Rachmad Setijadi

Keyword(s):

Compressive Strength ◽

Chloride Ion ◽

Concrete Surface ◽

Chloride Ions ◽

Calcium Stearate ◽

Type I ◽

Compressive Strength Test ◽

Strength Tests ◽

Concrete Quality ◽

Infiltration Test

This study aims to determine the effect of calcium stearate on concrete. Three kinds of concrete quality are studied, namely, 20, 30, and 40 MPa. Tests performed in the laboratory comprise a compressive strength test and an infiltration test of chloride ion content. The specimens used were cylinders with a diameter of 150 mm and height of 300 mm. The chloride ion infiltration test was carried out on a cube with sides of 150 mm. The infiltration of ions into the concrete was examined at depths of 1, 2, 4, 6, and 8 cm. Four dosages of calcium stearate were added to the concrete, namely, 0, 0.25, 1.27, and 2.53% for 20 MPa concrete; 0, 0.21, 1.07, and 2.48% for 30 MPa concrete; and 0, 0.19, 0.90, and 1.87% for 40 MPa concrete. The results of compressive strength tests indicate that the amount of calcium stearate that could be safely applied to the concrete was 0.25% of the weight of cement. On the other hand, the infiltration of chloride ions at a depth of 6 cm from the unprotected concrete surface decreased by 87, 69, and 113% for the 20, 30, and 40 MPa concrete, respectively, compared to concrete without calcium stearate. The test shows that the use of calcium stearate in concrete significantly increases its resistivity against corrosion attacks because, in the absence of chloride ions, the process of corrosion does not take place in the concrete.

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Effects of Hydrogen Evolution During ECE on the Bond Strength between Steel and Concrete

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.602-604.952 ◽

2012 ◽

Vol 602-604 ◽

pp. 952-956

Author(s):

Chun Lin Deng ◽

Yun Xu ◽

Jian Bo Xiong ◽

Sheng Nian Wang

Keyword(s):

Adverse Effects ◽

Bond Strength ◽

Hydrogen Evolution ◽

Current Density ◽

Concrete Surface ◽

Total Charge ◽

Steel Reinforced Concrete ◽

Pull Out ◽

Electrochemical Chloride Extraction ◽

Corrosion Of Steel

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.

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Effect of electrochemical chloride extraction treatment on the corrosion of steel rebar in chloride contaminated mortar

Anti-Corrosion Methods and Materials ◽

10.1108/acmm-12-2014-1473 ◽

2016 ◽

Vol 63 (5) ◽

pp. 377-385 ◽

Cited By ~ 3

Author(s):

The Huyen Nguyen ◽

Tuan Anh Nguyen ◽

Van Khu Le ◽

Thi Mai Thanh Dinh ◽

Hoang Thai ◽

...

Keyword(s):

Compressive Strength ◽

Chloride Ions ◽

Electric Resistivity ◽

Sodium Borate ◽

Content Type ◽

Steel Rebar ◽

Free Chloride ◽

Electrochemical Chloride Extraction ◽

Corrosion Of Steel ◽

Chloride Contaminated

Purpose This work aims to demonstrate the use of electrochemical chloride extraction (ECE) to remove chloride ions away from the steel rebar in chloride-contaminated mortar and to mitigate the corrosion of the embedded steel. Design/methodology/approach To simulate salt contamination in concrete, sodium chloride was added at 0.5 per cent by weight of cement in the fresh mortar featuring a water-to-cement ratio of 0.45. The ECE treatments were varied at two electrical current densities (1 and 5 A/m2), using two electrolytes (0.1M NaOH and 0.1M Na3BO3 solutions) and for two periods (2 and 4 weeks). The average free chloride concentration in cement mortars before and after ECE treatment was quantified using a customized chloride sensor, whereas the spatial distribution of relevant elements was obtained using energy-dispersive X-ray spectroscopy. The effect of ECE treatment on the electric resistivity of mortar and the corrosion resistance of steel rebar was investigated by electrochemical impedance spectroscopy and potentiodynamic polarization measurements, respectively. Findings The experimental results reveal that the ECE treatment was effective in removing chlorides and in improving electric resistivity and compressive strength of the mortar, when using the sodium borate solution as the electrolyte. In this case, a 4-week ECE treatment at 1 A/m2 decreased the free chloride content in the mortar by 70 per cent, significantly increased the Ca/Si ratio in the mortar near rebar, led to a more refined and less permeable microstructure of the mortar and significantly improved its compressive strength. The ECE treatment was able to halt the chloride-induced corrosion of steel rebar by passivation. A 4-week ECE treatment at 1 A/m2 using sodium hydroxide and sodium borate solutions decreased the corrosion rate of rebar by 36 and 34 per cent, respectively. Originality/value This electrochemical rehabilitation of steel-reinforced concrete under chloride-contaminated condition is very effective in prolonging its service life.

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Galvanic chloride extraction by an embedded zinc anode: Ion distribution mapped by laser induced breakdown spectroscopy (LIBS)

MATEC Web of Conferences ◽

10.1051/matecconf/201928903010 ◽

2019 ◽

Vol 289 ◽

pp. 03010

Author(s):

W. Schwarz ◽

Gerd Wilsch ◽

A. Pichlhöfer ◽

G. Ebell ◽

T. Völker

Keyword(s):

Concrete Surface ◽

Chloride Ions ◽

Laser Induced Breakdown Spectroscopy ◽

Ion Distribution ◽

Ion Migration ◽

Zinc Anode ◽

Steel Reinforced Concrete ◽

Breakdown Spectroscopy ◽

Steel Rebar ◽

Laser Induced Breakdown

An important aspect with regard to the service life of zinc based galvanic anodes and the durability of the corrosion protection of steel in concrete is the “galvanic chloride extraction”. Chloride ions move in the electric field generated by the current, flowing between the galvanic anode and the cathodic steel. Migration leads to an accumulation of anions, e.g. chloride ions, at the anode and depletion of chlorides near the steel rebar surface. The ion migration was studied on steel reinforced concrete specimens admixed with 3 wt.% chloride/wt. cement and galvanically protected by a surface applied embedded zinc anode (EZA). The zinc anode was embedded and glued to the concrete surface by a geo-polymer based chloride free binder. The EZA was operated over a period of 1 year and the ion distribution between anode (EZA) and cathode (steel reinforcement) was studied by laser induced breakdown spectroscopy (LIBS) after 5 months, 7 months and 12 months. The results show that chloride ions efficiently migrate in the direction of the zinc-anode and accumulate there. Chloride distribution in the EZA correlates with the distribution of zinc ions generated by the anodic dissolution of the zinc anode in the binder matrix. The microstructure of the binder matrix and its interface to the zinc-anode are studied by REM/EDX – preliminary results will be reported.

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