By EHAB HASUNA

Electrochemical Chloride Extraction (ECE)

By Ehab

M.Hasuna

INTRODUCTION ECE PROCESS ADVANTAGES OF ECE DISADVATAGES OF ECE EXPERMINTAL STUDIES ON ECE CONCLUSION REFRENCESS

OUTLINE

Electrochemical chloride extraction is a non-destructive treatment which :

a)  Extracts chloride ions from contaminated concrete.

b) Reinstates the passivity of steel reinforcement. 

c)  Produces a high pH environment.

d)  Re-establish the original properties and allows the concrete to continue in service without further concerns.

WHAT IS ELECTROCHEMICAL CHLORIDE EXTRACTION (ECE) ?

ECE accomplished by applying auxiliary anode and electrolyte to structure surface, and passing direct current between this anode and reinforcing steel which acts as a cathode.

It aims to move chloride ions away from reinforcing steel and out of the concrete structure.

The speed of chloride removal depends on the magnitude of the applied current.

During ECE the electrochemical reaction occurring at the steel surface also increases the alkalinity of surrounding concrete through the generation of hydroxyl ions, which repassivates the steel by achieving chloride/hydroxyl ratios lower than initiation threshold level .

HOW DOES ECE WORK?

Nor cure chloride extraction process ECE SYSTEM

.

http://www.vector-corrosion.com/systemsservices/electro-chemical/chloride-extraction/

http://www.vector-corrosion.com/systemsservices/electro-chemical/chloride-extraction/ .

INTERNAL AND EXTERNAL PARAMETERS THAT INFULANCE THE (ECE) PERFORMANCE Chloride binding. Cement type. Alkalinity. Temperature. Aggregate. Current density. Rebar configuration.

Environmentally friendly: Major reduction of concrete breakout.

Long term global protection: Provides effective treatment for the entire area of application.

Proven technology: Long history and an excellent track record.

Treatment completed in 4 to 8 weeks with no further maintenance.

Temporary power supply can be used , no mains required.

ADVANTAGES

New technology , few standards or specifications available yet.

High charge density can cause some problems.

Lifetime treatment not well defined yet.

Require specialist knowledge.

DISADVANTAGES

ECE has gradually gained acceptance as an effective method for nondestructive treatment of concrete where chloride ingress has occurred to such an extent that may induce steel corrosion.

The treatment usually utilizes a current density of 1-5 A/m2 (electrical field of less than 41V for safety reasons) for 4-8 weeks.

Removed chloride can range between 40 and 60%.

EXPERMINTAL STUDIES ON ECE

In 1993, a few studies 22-24 funded by the Strategic Highway Research Program (SHRP) investigated the effectiveness of ECE as a rehabilitation measure for concrete bridge components, as well as the adverse side effects of elevated system current, such as increased concrete permeability, decreased steel-concrete bond, and cracking of the concrete.

In a study by Minnesota Department of Transportation in 1999 25, although the ECE process reduced chloride levels in the treated structures by approximately 50%, several locations in the structures following ECE still had chloride concentrations in excess of the chloride threshold level.

.

Higher chloride extraction was obtained in non-carbonated concrete than in carbonated concrete irrespective of the configuration of the reinforcement system.

Accumulations of alkali ions were greater in the non-carbonated concrete specimens.

Effect of Carbonation on ECE

According to some experimental studies it has been observed that concrete reinforced with multiple mats having the rebars directly placed over each other showed better chloride removal than those in which the rebars were displaced with respect to one another.

Effect of Rebar Configuration on ECE

It was observed that circular columns containing spiral reinforcements showed better ECE performance than structures within planar surfaces.

Practical studies implication is that supplemental ECE application may be more necessary in systems with planar surfaces than those with geometrically curved surfaces.

Effect of Structural Shape on ECE

ECE can be effective method of removing chloride ions but during this process many side effects may occur inside the treatment concrete.

.

CONCLUSION

Electrochemical realkalisation and chloride extraction treatments for reinforced concrete, CEN / TS 14038 -1.

Standard Practice: Electrochemical realkalisation and chloride extraction treatments for reinforced concrete, NACE SP0107-2007.

Concrete society :Electrochemical realkalization and chloride extraction treatments for reinforced concrete, Part 2: Chloride extraction. 

J. Bennett, K.F. Fong, and T.J. Schue, Electrochemical Chloride Removal and Protection of Concrete Bridge Components: Field Trials, Strategic Highway Research Program, Washington DC, USA, Report #SHRP-S-669, 1993.

REFRENCESS