ACI RAP Bulletin 8

®
American Concrete Institute
Advancing concrete knowledge

FIELD GUIDE TO Installation of

CONCRETE REPAIR Embedded
APPLICATION PROCEDURES Galvanic Anodes

Installation of Embedded Galvanic Anodes (ACI RAP-8) 1

2 Repair Application Procedures Bulletin
 ACI RAP Bulletin 8

Field Guide to Concrete Repair Application Procedures

Installation of Embedded Galvanic Anodes

Reported by ACI Committee E706

David W. Whitmore*
Chair

J. Christopher Ball Fred R. Goodwin Kenneth M. Lozen Jay H. Paul

Peter H. Emmons Bob Joyce John S. Lund George I. Taylor
Timothy R. W. Gillespie Brian F. Keane Kelly M. Page Patrick M. Watson
H. Peter Golter

*
Primary author.

It is the responsibility of the user of this document to Structural Disclaimer

establish health and safety practices appropriate to the specific
circumstances involved with its use. ACI does not make any This document is intended as a voluntary field guide for
representations with regard to health and safety issues and the use the Owner, design professional, and concrete repair con-
of this document. The user must determine the applicability of tractor. It is not intended to relieve the user of this guide
all regulatory limitations before applying the document and of responsibility for a proper condition assessment and
must comply with all applicable laws and regulations,
including but not limited to, United States Occupational structural evaluation of existing conditions, and for the
Safety and Health Administration (OSHA) health and specification of concrete repair methods, materials, or
safety standards. practices by an experienced engineer/designer.

ACI Repair Application Procedure 8.

Copyright © 2005, American Concrete Institute.
All rights reserved including rights of reproduction and use in any The Institute is not responsible for the statements or
form or by any means, including the making of copies by any photo pro- opinions in its publications. Institute publications are
cess, or by electronic or mechanical device, printed, written, or oral, or
recording for sound or visual reproduction or for use in any knowledge not able nor intended to supplant individual training,
retrieval system or device, unless permission in writing is obtained from responsibility or judgment of the user, or the supplier of
the copyright proprietors. Printed in the United States of America. the information provided.

Installation of Embedded Galvanic Anodes (ACI RAP-8) 3

Introduction
In the last 20 years, there has been an increase in the need
for concrete rehabilitation. In many structures, exposure to
deicing chemicals and marine-sourced chloride is a signifi-
cant cause of corrosion, playing a more detrimental role than
originally anticipated. Corrosion of reinforcing steel within
concrete is recognized as a significant problem facing
present-day owners and engineers.
The most common procedure for repairing deteriorated
concrete involves the removal of the damaged material and
replacement with new concrete or mortar. While this
addresses the immediate serviceability requirements, it does
not always satisfy long-term durability needs. Differences in
Fig. 1—“Ring-anode” corrosion.
pH, porosity, and chloride content are a few of the factors
that may result in corrosion activity. As a result, “chip and
patch-style” repairs may fail prematurely in chloride-
exposed structures.
Repair of corrosion-related deterioration in concrete struc-
tures offers unique challenges. In particular, the “ring-
anode” effect, also called the “halo” effect (Fig. 1), is a
phenomenon that is frequently overlooked but is a common
cause of premature patch failure or increased repair volume.
Generally stated, the ring-anode effect describes the increase
in corrosion activity adjacent to a repair area. The ring-anode
effect is caused by the electrochemical incompatibility
between reinforcing steel within a patch and the steel
embedded within the surrounding concrete. Fig. 2—Chloride-accelerated corrosion.
Galvanic technology—Galvanic methods of corrosion
protection have been developed for use in concrete. These
methods are used to combat the underlying corrosion rather
than simply repairing the physical damage. By supplying a
small electrical current to the reinforcing steel, one can slow
down corrosion of the steel. Galvanic systems are desirable
because they create their protective current internally
through a natural reaction wherein the anode corrodes to
galvanically protect the reinforcing steel.
Embedded galvanic anodes—Embedded galvanic anodes
are installed by burying them within the concrete. Type 1
embeddable galvanic anodes are available to be included in
standard concrete repair (Fig. 2) or along a joint between
new and existing concrete. Type 2 embeddable galvanic Fig. 3—Chloride-accelerated corrosion.
anodes are designed to be installed in sound concrete (Fig. 3).
When Type 1 anodes are included in a concrete repair, they When do I use this method?
are typically installed at the perimeter of a repair area to be Embedded galvanic anodes are attached to reinforcing
in the immediate area of concern. When a suitable concrete steel within the patch cavity to protect the steel in concrete
or mortar is placed around the anode, it begins to sacrificially adjacent to the patch. For repairs in either chloride-contami-
protect the adjacent reinforcement. nated or carbonated concrete, embedded galvanic anodes can
be incorporated in the repair to minimize corrosion of the
What is the purpose of this repair? reinforcing steel adjacent to the repair. Embedded galvanic
Embedded galvanic anodes reduce the corrosion activity anodes can also be attached to reinforcement at the interface
of the reinforcing steel in the vicinity of the installed anode. of new and existing chloride-contaminated concrete. Exam-
Anodes are installed in areas of the concrete where there is a ples of uses include bridge deck widening, replacement of
high likelihood of corrosion occurring or recurring. Type 1 deck joint nosings, or concrete pile jacketing.
anodes are installed to provide improved protection of rein- During concrete condition inspections, areas of potentially
forcing steel in chloride-contaminated or carbonated active corrosion of the reinforcing steel are often discovered in
concrete surrounding a patch repair. Type 2 anodes are used mechanically sound concrete. Embedded galvanic anodes can
in sound chloride-contaminated or carbonated concrete to be installed in these areas to delay corrosion damage to the
prevent the onset of delamination or spalling of the concrete. concrete. These anodes can be installed on a grid pattern over

4 Repair Application Procedures Bulletin

Fig. 4—Deteriorated concrete removed. Fig. 5—Checking continuity of reinforcing steel.

a large area to provide protection for reinforcing steel in pational Safety and Health Administration (OSHA) health
concrete that is found to be or is suspected to be contaminated. and safety standards.

How do I prepare the surface? Preconstruction meeting

Complete surface preparation as required for the application Prior to proceeding with the repair, a preconstruction
of the repair concrete or mortar. Limit the use of bonding meeting is recommended. The meeting should include repre-
agents to those with low resistivity, such as slurries containing sentatives from all participating parties (owner, engineer,
portland cement or portland cement-sand mixtures. Avoid contractor, materials manufacturer, etc.), and specifically
insulating materials such as epoxy bonding agents. address the parameters, means, methods, and materials
necessary to achieve the repair objectives.
How do I select the right material?
Embedded galvanic anodes should be used only in conjunc-
Repair procedure
tion with cementitious or cementitious-polymer repair
Anode spacing in either repair type is often determined by
materials, which have a low resistivity. Resistivity of repair
the engineer, and differs for each situation. Spacing of the
materials or concrete for use with embedded galvanic anodes
anodes is mainly a function of steel density and the corrosive-
should be less than 15,000 ohm-cm. High-resistivity materials
ness of the environment. Structures with heavy reinforcement
such as epoxies or highly polymer modified repair mortars
or structures in highly corrosive environments often require
greatly reduce the available galvanic current or prevent the
closer spacing for the anodes to function effectively.
anodes from functioning properly. If a low-resistivity material
is not suitable for the full repair, anodes can be embedded in Type 1 embedded anodes installed in standard repairs—
individual pockets of low-resistivity material. These pockets As in standard patch repairs, all deteriorated concrete should
should completely encapsulate the anode and completely fill be removed from around and behind the reinforcing steel
the space between the anode and the concrete substrate. inside the repair area in accordance with good concrete
repair practice (Fig. 4). Sufficient clearance between the
What equipment do I need? anode and the substrate concrete should be provided
The equipment needed to install Type 1 embedded (minimum of 3/4 in. [19 mm] or 1/4 in. [6 mm] larger than
galvanic anodes in standard repairs entails only basic hand the nominal maximum size of the coarse aggregate used in
tools and a DC ohm meter capable of reading 0 to 200 ohms. the repair material, whichever is greater). The exposed rein-
To install Type 2 embedded galvanic anodes in sound forcing bar in the repair area should be thoroughly cleaned
concrete, the equipment required includes a reinforcing bar and at least the visible surfaces should be cleaned to a bright
locator, percussion drill or core drill, basic hand tools, and metal surface to facilitate good electrical connections where
DC ohm meter. the anodes are attached. Prior to installation, electrical conti-
nuity of the reinforcing bar within the repair area should be
What are the safety considerations? confirmed with the use of a DC ohm meter (Fig. 5).
It is the responsibility of the user of this document to Anode spacing is as specified by the engineer, with the
establish health and safety practices appropriate to the anodes placed along the perimeter of the repair area. Each
specific circumstances involved with its use. ACI does not anode should then be securely connected to the reinforcing
make any representations with regard to health and safety steel (Fig. 6 and 7). If less than 1 in. (25 mm) of cover exists,
issues and the use of this document. The user must determine the anode should be placed beneath the bar (away from the
the applicability of all regulatory limitations before applying surface of the concrete). Once installed, the electrical
the document and must comply with all applicable laws and connection between the anode and the reinforcing steel
regulations including, but not limited to, United States Occu- should be confirmed (Fig. 8). The resistance of the electrical

Installation of Embedded Galvanic Anodes (ACI RAP-8) 5

Fig. 6—Tying tool and anode. Fig. 9—Locating reinforcing steel.

Fig. 7—Tying in anode. Fig. 10—Coring hole for anode.

Fig. 11—Secondary hole with reinforcing steel connection.

Fig. 8—Confirming connection to reinforcing steel.

on the location of the reinforcing steel, the anode location
connection should be less than 1 ohm. Finally, the patch should be marked, and a hole of appropriate size should be
cavity is filled with a compatible repair material, using drilled to accommodate the anode (Fig. 10). A location for
normal patching procedures and taking care to completely connection of the anode to the reinforcing steel should then
encase the anode. be marked, drilled if necessary, and a connection made
Type 2 embedded anodes installed in sound concrete— (Fig. 11), either within the original hole or in a secondary
Reinforcing steel in the area of the desired installation should hole. Continuity of the reinforcing steel in the location of instal-
be located and marked on the concrete surface (Fig. 9). Based lation should be verified with a DC ohm meter.

6 Repair Application Procedures Bulletin

Fig. 12—Confirming connection to reinforcing steel. Fig. 13—Anode placed in hole with patching material.

All holes should be cleaned of debris and dust. The anode Sources for additional information
should be securely connected to the reinforcing steel, and the ACI Committee 222, 2001, “Protection of Metals in Concrete Against
contact should be confirmed using the DC ohm meter (Fig. 12). Corrosion (222R-01),” American Concrete Institute, Farmington Hills,
Connection resistance should be less than 1 ohm. Any Mich., 41 pp.
connections between dissimilar metals (such as copper wires ACI Committee 546, 2004, “Concrete Repair Guide (ACI 546R-04),”
American Concrete Institute, Farmington Hills, Mich., 53 pp.
to steel) should be sealed with silicone or a two-part epoxy
Bertolini et al., 1998, “Cathodic Protection and Cathodic Prevention in
to prevent localized corrosion. The drilled hole(s) can then
Concrete: Principles and Applications,” Journal of Applied Electrochemistry,
be filled using the appropriate repair material (Fig. 13).
V. 28, pp. 1321-1331.
Glass, G.; Taylor, J.; Roberts, A.; and Davison, N., 2003, “The Protec-
How do I check the repair? tive Effects of Electrochemical Treatment in Reinforced Concrete,” NACE
Embedded galvanic anodes, when normally installed,
Paper No. 03291, Corrosion 2003.
allow for very few direct measurements other than those for Glass, G.K.; Hassenein, A.M.; and Buenfeld, N.R.; Corrosion Science,
corrosion potentials. If more-detailed performance data are V. 43, No. 6, 2001, pp. 1111-1131.
desired, anodes can be installed to allow monitoring of the Hausman, D. A., 1967, “Steel Corrosion in Concrete,” Material Protection,
current and voltage output of the anodes. With a switch pp. 19-23.
installed in the circuit, corrosion potential or corrosion International Concrete Repair Institute, 1995, “Guide for Surface Prepa-
potential decay measurements can also be taken, if appro- ration for the Repair of Deteriorated Concrete Resulting from Reinforcing
priate, to determine the level of polarization of the steel. Steel Corrosion,” ICRI Technical Guideline No. 03730.

Installation of Embedded Galvanic Anodes (ACI RAP-8) 7