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Standard Specification for

Electrochemical Chloride Extraction

AASHTO Designation: 
Draft Specification

1. Introduction 
- This standard
provides a specification for Electrochemical Chloride Extraction (ECE)
of a chloride contaminated concrete structure, i.e. a bridge sub-structure
or a bridge deck.

2.1 This standard
provides  installation and operation specifications for Electrochemical
Chloride Extraction of chloride contaminated concrete structures.

2.2 This standard may involve hazardous materials, operations, and
equipment.  It does not purport to address all of the safety problems
associated with its use.  It is the responsibility of whomever
uses this standard to consult and establish appropriate safety and health
practices and determine the applicability of regulatory limitations
prior to use.

3. Referenced Documents

3.1 AASHTO Designations

T 260-94 Sampling and Testing for Chloride Ion in Concrete and Concrete
Raw Materials

R 18 Establishing and Implementing A Quality System for Construction
Materials Testing Laboratories

3.2 ASTM Standards

C876-91 Measurement and Interpretation of Half-Cell Potentials of Reinforcing
Steel in Concrete

4. Terminology

4.1  Alternating
Current (AC) - Electric current which repeatedly reverses direction
on a periodic cycle, usually at a frequency of 60 cycles per second
(60 Hz).

4.2 A.C. Service
- Alternating current supply to the rectifier; 240 or 480 volts AC.

4.3 Anode - The electrode
at which oxidation reactions (i.e. corrosion reactions) occur, and to
which negatively charged ions migrate when an electric current is passed
through an electrolyte.  The anode may be any material that distributes
the ECE current to the entire surface to be treated.  Anode used
for  ECE shall be either catalyzed titanium, or steel as specified.

4.4 Anode Subzone
- An electrically isolated anode circuit within an Anode Zone occupying
an area not exceeding 200 ft<sup>2.  All subzones within
a zone operate in parallel.

4.5 Anode Zone
- An isolated anode circuit on the concrete surface occupying an area
not exceeding 1,500 ft<sup>2.

4.6 Cathode -
The electrode at which reduction occurs, and to which positively charged
ions migrate when an electric current is passed through an electrolyte. 
When applying ECE systems, the cathode is the embedded reinforcing steel.

4.7 Cell - An
electrochemical system consisting of an anode and a cathode in metallic
contact and immersed in an electrolyte. The anode and cathode may be
different metals.

4.8 Constant Current
- An operating mode in a rectifier in which the current is set at a
fixed level, and the voltage varies.  Variations in the rectifier
output voltage and current will occur with the changes in the concrete
resistance and AC line voltage.

4.9 Constant Voltage
- An operation mode in a rectifier in which the voltage is set at a
fixed level, and the current varies.  Variations in the rectifier
output voltage and current will occur with the changes in the bridge
deck resistance and AC line voltage.

4.10 Corrosion
- The natural tendency of a metal to revert to its native state because
of a reaction with its environment.  In order for corrosion to
occur there must be an anode, a cathode, an electrolyte and a conductive
path between the anode and cathode.

4.11 Current -
A movement of electricity through a solid or solution; commonly measured
in amperes or milliamperes.  In an ECE system, the direct current
flow is ionic (through the electrolyte) and electronic (through the
metallic paths).

4.12 Current Density
- The current per unit area of surface of metal or concrete.  A
common unit is A/m<sup>2 (amperes per square meter).

4.13 Direct Current
(D.C.) - Electric current that flows in only one direction.

4.14 D.C. Wiring
- All insulated conductors necessary for connecting the anode zones,
reinforcing steel and other instrumentation with the rectifier and/or
junction box.

4.15 ECE Installation
Supervisor (IS) - Representative who is familiar with all aspects of
the ECE process and its installation.

Note 1 - The
IS gives advice in the field regarding the installation and operation
of the ECE process and may perform necessary quality control field tests
to ensure proper system operation. The IS should have a minimum 1 year
of relevant experience with Electrochemical Chloride Extraction systems.

4.16 Electrical
Continuity - A closed circuit (unbroken electrical path) between metal
components under consideration.  For ECE of concrete structures,
continuity typically refers to the electrical connection of reinforcing
steel.

4.17 Electrical
Discontinuity - The physical separation  between  metal 
components  under consideration.   For ECE of concrete
structures, electrical discontinuity typically refers to discontinuous
or unconnected reinforcing steel.

4.18 Electrolysis
- Chemical changes in an electrolyte brought about by the passage of
an impressed electric current.

4.19 Electrolyte
- Any medium which serves as a conductor for the passage of ionic current
(i.e. concrete, soil and water).

4.20 Energize
- (turn on) The process of initially applying power to an ECE system.

4.21 Engineer
- The owner's representative or project engineer.

4.22 Filter -
A device used to increase the conversion efficiency of a rectifier.
Filters typically consist of an inductor or choke, which is used to
reduce the ripple component in the D.C. output.

4.23 Half-Cell
- A single electrode in contact with an electrolyte and which, in contact
with another half-cell, forms a full electrochemical cell. This term
is sometimes used to designate a reference electrode or reference cell.

4.24 Ion - An
atom or group of atoms that have lost or gained one or more electrons.
and have therefore acquired an electric charge (i.e. C1-,
OH-, H+, Na+).

4.25 Macro Cell
- A corrosion cell with a large anode to cathode relationship.

4.26 Meter - An
instrument which is used for measuring and recording such as in the
case of rectifier voltage, current and half-cell potential. Rectifier
meters may be analog or d