U.S. patent application number 16/451108 was filed with the patent office on 2019-12-26 for anode assembly for selective corrosion protection of metal parts in concrete.
The applicant listed for this patent is INPROM Est., Structural Group, Inc.. Invention is credited to Eyad Al Hariri, Wolfgang Schwarz.
Application Number | 20190390353 16/451108 |
Document ID | / |
Family ID | 68981025 |
Filed Date | 2019-12-26 |
United States Patent
Application |
20190390353 |
Kind Code |
A1 |
Al Hariri; Eyad ; et
al. |
December 26, 2019 |
ANODE ASSEMBLY FOR SELECTIVE CORROSION PROTECTION OF METAL PARTS IN
CONCRETE
Abstract
Disclosed is an anode assembly for the corrosion protection of
metal parts embedded in concrete. An ion-conducting material is
placed between the metal part that is to be protected and the
anode, which ion-conducting material exhibits higher ionic
conductivity than the surrounding concrete, thus directing the
protective current specifically towards the metal part. A galvanic
sacrificial anode may be provided, made, e.g., from zinc and its
alloys or aluminum and its alloys. The purpose of the material with
higher ionic conductivity than the surrounding concrete is to
selectively direct the protective galvanic current towards the
metal part that is to be protected. The selective enhanced
corrosion protection is especially beneficial for the protection of
metal parts that are highly important for the structural integrity
of concrete members, such as assembly of pre- or post-tensioning of
concrete members, such as anchor-heads. The ion conducting material
exhibits 20%, and more preferably 50%, higher conductivity than the
surrounding concrete. A suitable ion-conducting material that
exhibits ion-exchange properties may comprise tecto-alumo-silicate
materials. The anode may be placed in close contact to or may be
embedded into the ion-conducting material as well.
Inventors: |
Al Hariri; Eyad; (Columbia,
MD) ; Schwarz; Wolfgang; (Vienna, AT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Structural Group, Inc.
INPROM Est. |
Columbia
Triesen |
MD |
US
LI |
|
|
Family ID: |
68981025 |
Appl. No.: |
16/451108 |
Filed: |
June 25, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62689435 |
Jun 25, 2018 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23F 13/10 20130101;
C23F 2213/22 20130101; C23F 13/005 20130101; C23F 2201/02 20130101;
C23F 13/06 20130101; E04C 5/015 20130101 |
International
Class: |
C23F 13/00 20060101
C23F013/00; E04C 5/01 20060101 E04C005/01 |
Claims
1. A system for the corrosion protection of metal parts embedded in
a concrete member, comprising: a metal part embedded in said
concrete member; a first anode; and an ion-conducting material
between said metal part and said anode, said ion-conducting
material exhibiting higher ionic conductivity than concrete
embedding said metal part, and wherein said ion-conducting material
is configured to direct a corrosion-protective current towards said
metal part.
2. The system of claim 1, wherein the first anode is a galvanic
sacrificial anode.
3. The system of claim 1, wherein the first anode is composed of
zinc, zinc alloys, aluminum, or aluminum alloys.
4. The system of claim 1, wherein the first anode is composed of a
mesh, grid, perforated sheet, perforated plate, ribbons, perforated
ribbons, or strands.
5. The system of claim 1, wherein the ion-conducting material
exhibits at least 20% higher conductivity than said concrete
embedding said metal part.
6. The system of claim 1, wherein the ion-conducting material
exhibits at least 50% higher conductivity than said concrete
embedding said metal part.
7. The system of claim 1, wherein the ion-conducting material is
composed of a tecto-alumo-silicate material.
8. The system of claim 1, wherein the first anode is embedded into
the ion-conducting material.
9. The system of claim 1, wherein the ion-conducting material
contains a corrosion inhibitor.
10. The system of claim 1, wherein the metal part comprises steel
or cast iron.
11. The system of claim 1, wherein the metal part forms part of an
assembly for pre- or post-tensioning of concrete members.
12. The system of claim 1, wherein said ion-conducting material
fills an opening in said concrete formed by carving out a portion
of said concrete embedding said metal part.
13. The system of claim 12, further comprising a precast plug
formed from said ion-conductive material and inserted into said
opening and embedded into a bonding ion-conductive material.
14. The system of claim 13, wherein a galvanic anode is embedded in
said precast plug.
15. The system of claim 14, wherein said galvanic anode embedded in
said precast plug further comprises a galvanic sacrificial
anode.
16. The system of claim 14, wherein said galvanic anode embedded in
said precast plug is composed of zinc, zinc alloys, aluminum, or
aluminum alloys.
17. The system of claim 14, wherein said galvanic anode embedded in
said precast plug is composed of a mesh, grid, perforated sheet,
perforated plate, ribbons, perforated ribbons, or strands.
18. The system of claim 14, wherein said galvanic anode is wrapped
or folded.
19. The system of claim 14, wherein said first anode extends along
an exterior surface of said concrete member to provide a combined
galvanic protection of metal parts embedded in said concrete
member.
20. The system of claim 1, wherein said first anode is electrically
connected with single or multiple electrical connections for each
said metal part.
21. The system of claim 20, wherein the electrical connections are
made by welding, mechanically joining, or gluing.
22. The system of claim 21, wherein the electrical connections
comprise a conductive metal wire, strap, rod, or bar.
23. The system of claim 22, wherein the electrical connections
further comprise copper, zinc, aluminum, titanium, steel, or
stainless steel.
24. The system of claim 20, wherein the electrical connections are
made to any metallic member of a pre- or post-tensioned assembly
that includes said metal part.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/689,435 titled "Anode Assembly for Selective
Corrosion Protection of Metal Parts in Concrete," filed Jun. 25,
2018 by the inventors herein, which application is incorporated
herein by reference in its entirety.
FIELD OF THE INVENTION
[0002] This invention relates generally to the corrosion protection
of metal parts embedded in concrete, and more particularly to
systems and methods employing ion-conducting material to direct
corrosion-protective current from an anode to a concrete embedded
metal part.
BACKGROUND
[0003] Corrosion of steel reinforcement is one of the most
significant causes of elevated maintenance and repair costs and,
subsequently, of the shortening of the useful life of
steel-reinforced concrete structures. Corrosion of the steel
reinforcement is caused by the penetration of chlorides into the
covering and/or by carbonation of the concrete covering. Components
of civil engineering structures, such as bridges, tunnels, parking
garages, etc., that are frequently exposed to de-icing salt, and
structures such as harbor installations, bridges, apartment
buildings, etc., that are close to the sea and are exposed to sea
salt, are endangered and affected by chloride-induced corrosion of
the steel reinforcement, which corrosion is caused by chlorides
penetrating into the concrete. In such components, in the event of
damage, the chloride-contaminated concrete has to be removed down
to beyond the steel reinforcement and replaced by new fresh
concrete or repair mortar. However, this method of repair is very
complex, labor-intensive and costly.
[0004] An alternative to conventional repair of built structures
that have become endangered by the corrosion of the steel
reinforcement is cathodic corrosion protection (CCP), as described,
for example, in EP1068164B1, which method has been in use for
approximately 30 years. An alternative and/or supplementary measure
to CCP which is also used is galvanic corrosion protection (GCP),
as described, for example, in AT 1344/2004, EP1135538, EP0668373
and in U.S. Pat. No. 4,506,485. The effect of GCP is based on the
formation of a galvanic element between a sacrificial anode and the
steel reinforcement of a concrete structure, with the concrete
acting as the electrolyte. The anode materials used in such GCP
systems are typically zinc and alloys thereof, and less commonly
aluminum and alloys thereof. The anode is typically installed
either on the concrete surface or in holes drilled in the component
that is to be protected. Such a galvanic anode system is described,
for example, in U.S. Pat. Nos. 6,022,469, 6,303,017, 6,193,857. A
galvanic anode that is installed on the concrete surface by
embedding the anode in an embedding zinc activating binder or
embedded into the concrete as an anode assembly is described in
U.S. Pat. No. 8,394,193B2 and in GB patent out of EP 2 313 352.
Galvanic surface anodes are described in U.S. Pat. No. 7,851,022
and in EP 05768008.4.
[0005] The specifications of each of the foregoing references are
hereby incorporated by reference in their entireties.
[0006] Structures that are exposed to high loads or whose design
demands slim dimensions are usually reinforced with pre-stressed or
post-stressed tendons. Such assemblies typically consist of two
anchor heads between which the tendon strands are tensioned. The
great advantage of tensioned concrete members are their ability to
sustain high loads, as well as the slim structures that may be
realized through their use. Usually, only a few tensioning
assemblies are installed in a concrete member. The structural
integrity of the post- or pre-tensioned concrete member relies
essentially on the tensioning assembly. Therefore, corrosion of the
parts of the tensioning assembly (such as the anchor head, wedges,
tendons, and strands) may lead to catastrophic failure of the
structure. For that reason, corrosion protection of the tensioning
assembly, especially in post-tensioned structures, is essential.
Usually, if only a few tensioning assemblies--e.g., in bridges,
five tendons over the entire bridge deck--are damaged by corrosion,
the whole structure loading capacity could be compromised and in
need of extensive repairs or replacement. For concrete members,
e.g., balconies, the failure of only one part of the tensioning
assembly necessitates the replacement of the concrete member.
[0007] Therefore, the selective corrosion protection of the parts
of the tensioning assembly in such concrete structures is essential
for assuring the projected service time of the structure and the
concrete members.
SUMMARY OF THE INVENTION
[0008] Disclosed herein is an anode assembly for the corrosion
protection of metal parts embedded in concrete. An ion-conducting
material is placed between the metal part that is to be protected
and the anode, which ion-conducting material exhibits higher ionic
conductivity than the surrounding concrete, in turn directing the
protective current specifically towards the metal part. In
accordance with certain aspects of an embodiment of the invention,
a galvanic sacrificial anode is provided that is made from, e.g.,
zinc and its alloys or aluminum and its alloys. The purpose of the
material with higher ionic conductivity than the surrounding
concrete is to direct and selectively focus the protective galvanic
current towards the metal part that is to be protected. The
selective enhanced corrosion protection is especially beneficial
for the protection of metal parts that are highly important for the
structural integrity of concrete members, such as assemblies that
include pre- or post-tensioning of concrete members, such as
anchor-heads. In accordance with certain aspects of an embodiment
of the invention, the ion-conducting material exhibits 20%, and
preferably 50%, higher conductivity than the surrounding concrete
while at the same time exhibits no adverse effects on the steel
that is to be protected. In accordance with still further aspects
of an embodiment of the invention, an ion-conducting material is
placed that exhibits ion exchange properties, such as
tecto-alumo-silicate materials. The anode may be placed in close
contact to or may be embedded into the ion-conducting material.
[0009] In accordance with certain aspects of an embodiment of the
invention, a system for the corrosion protection of metal parts
embedded in a concrete member is provided, comprising: a metal part
embedded in the concrete member; a first anode; and an
ion-conducting material between the metal part and the anode, the
ion-conducting material exhibiting higher ionic conductivity than
concrete embedding the metal part, and wherein the ion-conducting
material is configured to direct a corrosion-protective current
towards the metal part.
BRIEF DESCRIPTION OF THE FIGURES
[0010] The novel features of the invention are set forth with
particularity in the appended claims. A better understanding of the
features and advantages of the present invention will be obtained
by reference to the following detailed description that sets forth
illustrative embodiments, in which the principles of the invention
are utilized. The present invention is illustrated by way of
example, and not by way of limitation, in the figures of the
accompanying drawings, in which like reference numerals refer to
similar elements, and in which:
[0011] FIG. 1 is a sectional perspective view of a prior art
concrete tensioning system in which embodiments of the invention
may be applied.
[0012] FIG. 2 is a sectional schematic view of an anode assembly
for selective corrosion protection of metal parts in concrete in
accordance with certain aspects of an embodiment of the
invention.
[0013] FIG. 3 is a section schematic view of an anode assembly for
selective corrosion protection of metal parts in concrete in
accordance with further aspects of an embodiment of the
invention.
[0014] FIG. 4 is a section schematic view of an anode assembly for
selective corrosion protection of metal parts in concrete in
accordance with still further aspects of an embodiment of the
invention.
[0015] FIG. 5 is a section schematic view of an anode assembly for
selective corrosion protection of metal parts in concrete in
accordance with still yet further aspects of an embodiment of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] The invention may be understood by referring to the
following description and accompanying drawings. This description
of an embodiment, set out below to enable one to practice an
implementation of the invention, is not intended to limit the
preferred embodiment, but to serve as a particular example thereof.
Those skilled in the art should appreciate that they may readily
use the conception and specific embodiments disclosed as a basis
for modifying or designing other methods and systems for carrying
out the same purposes of the present invention. Those skilled in
the art should also realize that such equivalent assemblies do not
depart from the spirit and scope of the invention in its broadest
form.
[0017] Descriptions of well-known functions and structures are
omitted to enhance clarity and conciseness. The terminology used
herein is for the purpose of describing particular embodiments only
and is not intended to be limiting of the present disclosure. As
used herein, the singular forms "a", "an" and "the" are intended to
include the plural forms as well, unless the context clearly
indicates otherwise. Furthermore, the use of the terms a, an, etc.
does not denote a limitation of quantity, but rather denotes the
presence of at least one of the referenced item.
[0018] The use of the terms "first", "second", and the like does
not imply any particular order, but they are included to identify
individual elements. Moreover, the use of the terms first, second,
etc. does not denote any order of importance, but rather the terms
first, second, etc. are used to distinguish one element from
another. It will be further understood that the terms "comprises"
and/or "comprising", or "includes" and/or "including" when used in
this specification, specify the presence of stated features,
regions, integers, steps, operations, elements, and/or components,
but do not preclude the presence or addition of one or more other
features, regions, integers, steps, operations, elements,
components, and/or groups thereof.
[0019] Although some features may be described with respect to
individual exemplary embodiments, aspects need not be limited
thereto such that features from one or more exemplary embodiments
may be combinable with other features from one or more exemplary
embodiments.
[0020] For experts knowledgeable of the state of the art of
electrochemical corrosion protection--e.g., cathodic corrosion
protection and/or galvanic corrosion protection--it is commonly
known that the degree of protection depends on the amount of
protective current arriving at the metal part that is to be
protected. One of the parameters determining the amount of current
arriving at the metal part that is to be protected is the
resistivity, and more particularly the electrolytic conductivity,
of the material placed between the anode and the metal part that is
to be protected, which material serves as the electrolyte. Concrete
is commonly used as the electrolyte for the cathodic protection of
steel in concrete in civil structures. However, the electrolytic
resistivity of concrete depends strongly on the humidity of the
concrete and may range from about 100 Ohm.m in humid concrete (95%
rh) up to several KOhm.m in dry concrete (50% rh) [1], covering a
range of 3 orders of magnitude. Concrete exposed to variable
weathering conditions may therefore show locally and over time
large variations in concrete resistivity. Therefore, metal parts
embedded into the concrete, such as an assembly for pre- or
post-tensioning of concrete members consisting of an anchor head,
wedges and steel tendons tensioned between the anchor heads, are
difficult to reliably and durably protect from corrosion using
electrochemical techniques. An exemplary prior art tensioning
system is shown in FIG. 1, depicting a concrete structure (shown
generally at 10), an anchor plate 12 embedded in concrete structure
10 and receiving an anchor head 14, which anchor head 14 receives
tendons 16 which, in turn, provide tension to concrete structure
10. A pocket or opening 18 is formed in the concrete structure 10,
to which a grout cap is typically applied to finish the
installation.
[0021] Usually, if one of the assemblies shown in FIG. 1 fails,
e.g., due to corrosion, then the concrete member 10 may suffer
irreparable damage rendering it unusable until extensive repairs or
replacement are undertaken. The most aggressive type of
steel-corrosion is initiated by ingress of chlorides that are
difficult to be sealed off. The most economic and well-established
corrosion protection techniques are based on electrochemical
corrosion protection techniques such as cathodic protection (CP).
However, the size of, e.g., anchor heads made from steel may be as
small as 2-3 inches in diameter. Therefore, small local variations
of concrete resistivity may lead to local lack of corrosion
protection. While this might be less crucial for the protection of
mild steel reinforcement that is available in large quantities
within reinforced concrete structures, corrosion on specific
elements of pre- or post-stressed reinforcement elements could
prove to be catastrophic to the structure, especially at the anchor
area.
[0022] One may apply high currents or high voltages to assure that
there is sufficient current flowing towards, e.g., the anchor heads
of post-tensioned concrete structures. However, these parts are
sensitive to hydrogen embrittlement. Hydrogen embrittlement may
only be avoided with high expenditure, involving use of a high
number of sensors (reference cells) and expensive control and
regulation equipment and software.
[0023] Another option is corrosion protection with sacrificial
galvanic anodes. Using zinc anodes, conditions of hydrogen
evolution and subsequent hydrogen embrittlement may be avoided due
to the maximum polarized potential of the steel. However, galvanic
corrosion protection systems do not allow the adjustment of the
applied current. The applied voltage is given by the system, and
with concrete being the electrolyte between the galvanic anode and
the metal parts that are to be protected, the current output is
controlled by the concrete resistivity. Potentially, galvanic
protection would be very suitable for protecting metal parts
embedded into the concrete (such as, e.g., anchor heads of pre- and
post-tensioning systems) if one can assure that enough current is
reaching the sensitive parts of the tensioning system.
[0024] In accordance with certain aspects of the invention, a
system and method are therefore provided to assure the reliable and
durable protection of metal parts that are highly important for the
structural integrity of concrete members, such as assemblies of
metal parts for the pre- or post-tensioning of concrete members
(e.g., anchor-heads). That system and method include placing an
ion-conducting material that exhibits a significantly higher ion
conductivity than the surrounding concrete between the anode,
preferentially a galvanic anode, and the metal part that is to be
protected. Preferably, the ion conductive material has an
electrolytic conductivity that is at least 20%, and more preferably
50%, higher than that of the surrounding concrete, and whose
dependence of the electrolytic conductance has a significantly
lower dependence on ambient humidity. In accordance with certain
aspects of an embodiment of the invention, suitable materials
include, e.g., electrolyte gels based on poly-ethylene oxide (PEO),
poly acrylonitrile (PAN), poly methyl methacrylate (PMMA), and poly
vinylidene fluoride (PVdF), or materials with ion exchange
properties such as ion exchange resins. An ion exchange resin on
expanded poly-styrene basis and a PEO-based electrolyte gel proved
to be suitable. However, organic materials tend to have a limited
service time and weathering resistance. Suitable ion-conducting
materials are also described in U.S. Pat. No. 7,851,022 and in EP
05768008.4. An inorganic material with ion exchange properties,
based on tecto-alumosilicate, and described in U.S. Pat. No.
8,394,193 B2, proved to be highly suitable. These hardened
tecto-alumosilicate binders may be applied like a fine mortar that
hardens within 1-6 hours and exhibits ion-exchange properties and
therefore good ion-conductive properties that are much less
dependent on ambient humidity than the electrolytic resistivity of
concrete. Typical electrolytic resistivities of the
tecto-alumosilicate binders described in U.S. Pat. No. 8,394,193 B2
are 50 Ohm.m at 75% ambient rh and 200 Ohm.m at 50% rh. On the
other hand, resistivities of standard concrete (w/c 0.5-0.45) are
in the range of about 100-1500 Ohm.m at 80% ambient rh,
1000-100,000 Ohm.m in dry concrete at 50% rh, and in carbonated
concrete about 10,000-15,000 Ohm.m [1, 2]. Therefore, anodes placed
on or into concrete and whose electrolytic contact with the metal
part that is to be protected, e.g. an anchor head, is made solely
by concrete, may not deliver sufficient protective current or may
fail completely under dry conditions. This applies especially to
anodes applied on concrete surfaces, as the surface layer of the
concrete may dry out rapidly and reduce the protective current
delivered by the anode, whereas the metal part embedded into the
concrete at a depth of 5 cm or more will still be in a humid
environment and, in presence of chloride, will continue to
corrode.
[0025] Therefore, by placing an ion-conducting electrolyte with a
significantly lower electrolytic resistivity than the surrounding
concrete, and which is significantly less sensitive to ambient
humidity, between the anode and the metal part that is to be
protected, one may assure that sufficient current reaches the
sensitive metal. In accordance with certain aspects of an
embodiment, the anode is preferentially a galvanic sacrificial
anode. Good results have been obtained with anodes made from zinc
and its alloys and aluminum and its alloys. Preferentially, the
anode consists of a mesh, grid, perforated sheet, perforated plate,
ribbons, perforated ribbons, or strands.
[0026] FIG. 2 is a schematic view of an exemplary configuration of
an anode assembly in accordance with certain aspects of an
embodiment of the invention. FIG. 2 shows a post-tensioned concrete
member 20 in which the anchor head 22, the anchor plate 23 and the
tensioned tendons 24 are embedded. The space between the outer
surface of concrete member 20 and the anchor head 22 and anchor
plate 23 is filled with tecto-alumosilicate binder 26 as described
above. A preferably zinc-mesh anode 27, placed on the outer surface
of the concrete member 20, is embedded into an embedding zinc
activating binder 28, which is preferably similar or identical to
the tecto-alumosilicate binder 26. The zinc-mesh anode 27 is
electrically connected through, e.g., the soft steel reinforcement
that is electrically connected to the tensioning assembly (i.e.,
anchor head 22, anchor plate 23, and tensioned tendons 24), or is
directly connected to the steel anchor plate 23, e.g., via an
electrical wire (not shown).
[0027] Tecto-alumosilicate binders are usually made of two reactive
components--an alumo-silicate component and an alkaline activator
component containing a soluble alkali-silicate. A suitable binder
may comprise an aqueous suspension of an alumo-silicate or a
mixture of alumo-silicates into which a highly alkaline (pH >14)
alkali-silicate is mixed as an activator. The alumo-silicate
component has a ratio of
(CaO+MgO+Al.sub.2O.sub.3)/SiO.sub.2>0.5, and more preferably
>0.8. The binder sets and hardens in usually 0.5 hours to 6
hours, and more preferably within 1 hour, after mixing the two
reactive components. To control consistency such as fluidity and
shrinkage and strength, suitable fillers or aggregates, such as
ground marble or quartz sand, may be added to the binder. The
admixture of ground marble with a grain size distribution of 0.1-1
mm in a ratio of 1.5:1 of binder/filler resulted in a highly
suitable fluid mortar with a fluidity of 160 mm according to EN
1015-3. To allow the application of the binder on vertical concrete
members or overhead, the additives that increase thixotropy may be
admixed, e.g., to the alumo-silicate component. Suitable additives
are, e.g., based on cellulose-ethers with a molecular weight
ranging from 1000 to 100,000, more preferably from 5,000 to 25,000.
An admixture of glass fibers proved to be highly advantageous in
controlling shrinkage and crack formation.
[0028] In accordance with certain aspects of an embodiment of the
invention, the galvanic current flows from the zinc-mesh anode
preferentially and selectively to the anchor-head and the
anchor-plate, and additionally protects parts of the tendons D that
are eventually exposed to chloride. This anode assembly has the
advantage that the anchor head and anchor plate are protected
preferentially from corrosion by directing the galvanic current
towards these sensitive parts and additionally protecting the
tensioned tendons without interfering at all with the concrete
structure.
[0029] In accordance with further aspects of an embodiment of the
invention, the system and method described herein may also provide
the advantage of protecting metal-part assemblies that are composed
of different types of metals or metal alloys that are electrically
connected to each other. Usually, if different metals are connected
and embedded into a material that functions as an electrolyte, such
as concrete, then a galvanic element is formed. The less noble
metal acts as an anode and corrodes. Examples include, e.g., anchor
heads made from cast iron that are directly connected to tendons
made from high strength steel alloyed with manganese, forming a
galvanic couple. The anode assembly shown in FIG. 2 will eliminate
such galvanic elements, preventing corrosion induced by the contact
of different metals.
[0030] FIG. 3 is a schematic view of an exemplary configuration of
an anode assembly in accordance with further aspects of an
embodiment of the invention. In FIG. 3, the contact zone of the
anchor head 22 and anchor plate 23 with the ion-conductive material
26 is covered or coated with an alkaline cement 30 (>pH 11),
preferably Portland cement Mortar, allowing the use of
ion-conductive materials with pH<11.
[0031] The present invention is not only applicable for new
structures but also for structures already in use or for concrete
members already cast and ready to be used. In that case, the grout
cap over the anchor head and anchor plate (discussed above with
respect to FIG. 1) may be removed by a suitable instrument or by
high pressure water jetting. Subsequently, the ion-conductive
material according to the invention may be placed and the anode
assembly installed as described above and shown in FIG. 2 or 3.
[0032] Further and with regard to FIG. 4, one may use precast plugs
40 made from an ion-conductive material as discussed above, which
plug 40 may be embedded into a suitable binder 26, preferably
formed of the same or similar material as the plug. This
configuration of the invention allows rapid installation of the
anode assembly.
[0033] With reference to FIG. 5, one may embed into the plug 40 an
anode 50, preferentially made from the same anode material as the
anode 27 that is installed at the concrete member surface. In this
configuration, the embedded anode 50 is equipped with a connecting
wire, strand or ribbon 52 to connect the plug anode 50 to the
surface anode 27. The embedded anode 50 is preferentially made from
mesh, grid, perforated sheets or perforated plate to allow the ion
current to flow freely between the surface anode 27 and the metal
part that is to be protected. The zinc mesh, grid or perforated
sheet may be folded ore that is wrapped to increase the amount of
anode material without impeding the ion-current flow. The
connecting wire, strand or ribbon consists of a suitable electric
conductive material, preferably the anode material, galvanized
steel, stainless steel, or titanium.
[0034] The additional anode inserted with the plug will prolong the
service life of the anode assembly.
[0035] If only the selective protection of metal parts without
additional protection of metal parts in the proximity is required,
then one may install only the precast plug 40, electrically
connecting the plug 40 to the metal part that is to be protected
(FIG. 4) without installing the surface anode 27. During galvanic
corrosion protection, the pH of the steel protected by the galvanic
anode will increase due to the alkali hydroxides formed near the
steel surface, assuring enhanced corrosion protection. However, to
enhance safety and durability of corrosion protection, the
electrolyte according to the present invention may contain at least
one corrosion inhibitor, preferably in electrolytes with a
pH<11.
[0036] Having now fully set forth the preferred embodiments and
certain modifications of the concept underlying the present
invention, various other embodiments as well as certain variations
and modifications of the embodiments herein shown and described
will obviously occur to those skilled in the art upon becoming
familiar with said underlying concept. It should be understood,
therefore, that the invention may be practiced otherwise than as
specifically set forth herein.
REFERENCES
[0037] [1] K. Osterminsky, R. Polder, P. Schiessl, Long term
behaviour of the resistivity of concrete, HERON Vol. 57 (2012) No.
3, pp 211-230. [0038] [2] Petrica Ionut I. Banea, Study of
Electrical Resistivity of Mature Concrete, MSc Thesis, Delft
University of Technology, Faculty of Civil Engineering and
Geosciences (Building Engineering) and TNO Structural Reliability
Department, Student number: 4125525, Delft, June 2015.
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