CA1337285C - Electrochemical re-alkalization of concrete - Google Patents
Electrochemical re-alkalization of concreteInfo
- Publication number
- CA1337285C CA1337285C CA000590928A CA590928A CA1337285C CA 1337285 C CA1337285 C CA 1337285C CA 000590928 A CA000590928 A CA 000590928A CA 590928 A CA590928 A CA 590928A CA 1337285 C CA1337285 C CA 1337285C
- Authority
- CA
- Canada
- Prior art keywords
- carbonated
- concrete
- medium
- zone
- further characterized
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/60—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only artificial stone
- C04B41/61—Coating or impregnation
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/009—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone characterised by the material treated
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
- C04B41/4505—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements characterised by the method of application
- C04B41/4564—Electrolytic or electrophoretic processes, e.g. electrochemical re-alkalisation of reinforced concrete
- C04B41/4566—Electrochemical re-alcalisation
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G23/00—Working measures on existing buildings
- E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Structural Engineering (AREA)
- Architecture (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Mechanical Engineering (AREA)
- Civil Engineering (AREA)
- Aftertreatments Of Artificial And Natural Stones (AREA)
Abstract
A process is disclosed for re-alkalizing carbonated reinforced concrete. An electric current is impressed between adjacent areas of concrete, one of which has become carbonated with consequent loss of pH, and the other of which is adequately alkaline in pH. The impressed voltage causes a migration of hydroxyl ions from the higher pH region to the lower pH region, to effect an increase in pH of the carbonated region to a satisfactory level. The region of high pH concrete may be either non-carbonated areas of the original concrete or a temporarily applied layer of an alkaline electrolyte.
Description
ELECTROCHEMICAL RE-ALKALIZATION OF CONCRETE
The present invention concerns a method of re-alkalizing carbonated zones in concrete, and the like, in order to rehabilitate the condition of such concrete.
Reinforcement and other steel objects which are cast in concrete, cements or calcareous materials, such as mortar, plaster or gunite etc., are normally protected against corrosion because of the alkaline environment in the mass. Gradually however, the alkaline concentration is reduced by the absorption dioxide and sulphur trioxide. This absorption leads to a gradual neutralization of the alkaline environment. When the pH-value of the mass reaches 9,5 (approx.) the steel is no longer protected and corrosion is initiated.
The most well-known neutralization reaction is caused by the absorption of carbon dioxide, and is known as "carbonation".
Carbonation is already a serious problem today as is evidence by the structural damage to buildings caused by the corrosion of reinforced steel, which is turn reduces the cross-section of the steel, and leads to the penetration of the concrete overlay as well as reductions in strength.
Damage caused by carbonation easily becomes a serious matter and is both difficult and expensive to repair. Traditionally this type of damage is repaired by chopping away the carbonated zone, sandblasting the exposed steel, and then concreting or using gunite.
Sealing combined with elutriation or a filler is another approach. The result is seldom satisfactory as far as durability and load-carrying capability are concerned.
The purpose of the present invention is to find a means of repairing carbonated zones in concrete etc.
which produce better results than the methods already in existence.
. ;~, ~
One of the characteristics of carbonation is that the damage is usually restricted to the surface zones of the structure, i.e., in the zone down to the first layer of reinforcement. This is normally a thin zone in relation to the remainder of the concrete cross-section, which is non-carbonated and has a surplus of alkaline matter.
Aspects of the invention are as follows:
The method of re-alkalizing a carbonated zone of a concrete structure from an adjacent zone of alkaline medium, wherein the carbonated zone has a pH
substantially below 12, which comprises, (a) applying between said zones a direct current voltage of at least six volts to effect a migration of alkaline ions from said alkaline medium to said carbonated zone, (b) generally maintaining said voltage until said carbonated zone reaches a pH of about 12, and (c) thereafter discontinuing the application of said voltage.
A method of re-alkalizing carbonated zones in concrete etc., is characterized by an electric charge being passed between one reinforcement element in an area which has been carbonated and an electrode in an area with an alkaline environment.
The carbonated zone is supplied with alkaline either from the fresh interior of the concrete etc., or from an external electrolytic medium by employing electricity.
The re-alkalization from this alkaline matter re-establishes the corrosive protection of the steel.
2a The procedure is based on the following principle:
When a base electrolytic solution which contains calcium, sodium and potassium hydroxide, for example, is exposed to an electrical field between two electrodes, ions will be transported between the electrodes, which will make the area in the immediate vicinity of one of the electrodes highly alkaline. This alkaline content remains after the removal of the electrical field.
This procedure is executed in practice in the following way:
1. If the concrete etc., contains a double layer of reinforcement, where one layer is in carbonated concrete and the other is in fresh concrete, the reinforcement in the carbonated zone is connected to one pole on a rectifier or battery, whilst supplied, the alkaline hydroxyl-ions migrate to the reinforcement existing methods, such as pH-sensitive tracers or pH-electrodes. When the desired pH value is reached (usually over 12), the current can be disconnected.
The present invention concerns a method of re-alkalizing carbonated zones in concrete, and the like, in order to rehabilitate the condition of such concrete.
Reinforcement and other steel objects which are cast in concrete, cements or calcareous materials, such as mortar, plaster or gunite etc., are normally protected against corrosion because of the alkaline environment in the mass. Gradually however, the alkaline concentration is reduced by the absorption dioxide and sulphur trioxide. This absorption leads to a gradual neutralization of the alkaline environment. When the pH-value of the mass reaches 9,5 (approx.) the steel is no longer protected and corrosion is initiated.
The most well-known neutralization reaction is caused by the absorption of carbon dioxide, and is known as "carbonation".
Carbonation is already a serious problem today as is evidence by the structural damage to buildings caused by the corrosion of reinforced steel, which is turn reduces the cross-section of the steel, and leads to the penetration of the concrete overlay as well as reductions in strength.
Damage caused by carbonation easily becomes a serious matter and is both difficult and expensive to repair. Traditionally this type of damage is repaired by chopping away the carbonated zone, sandblasting the exposed steel, and then concreting or using gunite.
Sealing combined with elutriation or a filler is another approach. The result is seldom satisfactory as far as durability and load-carrying capability are concerned.
The purpose of the present invention is to find a means of repairing carbonated zones in concrete etc.
which produce better results than the methods already in existence.
. ;~, ~
One of the characteristics of carbonation is that the damage is usually restricted to the surface zones of the structure, i.e., in the zone down to the first layer of reinforcement. This is normally a thin zone in relation to the remainder of the concrete cross-section, which is non-carbonated and has a surplus of alkaline matter.
Aspects of the invention are as follows:
The method of re-alkalizing a carbonated zone of a concrete structure from an adjacent zone of alkaline medium, wherein the carbonated zone has a pH
substantially below 12, which comprises, (a) applying between said zones a direct current voltage of at least six volts to effect a migration of alkaline ions from said alkaline medium to said carbonated zone, (b) generally maintaining said voltage until said carbonated zone reaches a pH of about 12, and (c) thereafter discontinuing the application of said voltage.
A method of re-alkalizing carbonated zones in concrete etc., is characterized by an electric charge being passed between one reinforcement element in an area which has been carbonated and an electrode in an area with an alkaline environment.
The carbonated zone is supplied with alkaline either from the fresh interior of the concrete etc., or from an external electrolytic medium by employing electricity.
The re-alkalization from this alkaline matter re-establishes the corrosive protection of the steel.
2a The procedure is based on the following principle:
When a base electrolytic solution which contains calcium, sodium and potassium hydroxide, for example, is exposed to an electrical field between two electrodes, ions will be transported between the electrodes, which will make the area in the immediate vicinity of one of the electrodes highly alkaline. This alkaline content remains after the removal of the electrical field.
This procedure is executed in practice in the following way:
1. If the concrete etc., contains a double layer of reinforcement, where one layer is in carbonated concrete and the other is in fresh concrete, the reinforcement in the carbonated zone is connected to one pole on a rectifier or battery, whilst supplied, the alkaline hydroxyl-ions migrate to the reinforcement existing methods, such as pH-sensitive tracers or pH-electrodes. When the desired pH value is reached (usually over 12), the current can be disconnected.
2. If the concrete contains one layer of reinforcement, or possibly a second layer which is unaccessible, or if the distance between the two layers is too great for the techn;que described in point 1 to be feasible, an external electrode is located in a suitable electrolytic medium on the surface of the structure. This electrode can consist of wires, cords, plates, foil or sheet metal, conducting plastics or other conductive materials. The electrolyte can be an aqueous solution of calcium, sodium, potassium and their salts either in a liquid or absorbed in a porous medium such as rock wool, cellulose, sawdust, sand, clay and the like, or it can be strongly retarded concrete, mortar, cement grout, lime paste etc. When a cement-based concrete, mortar or paste is used, a strongly retarding substance such as sucrose is added to prevent the mass from setting, thus once the treatment is completed, this mass can be removed by scraping or flushing.
The external electrode is connected to one pole of the rectifier or battery, whilst the reinforcement in the carbonated zone is connected to the other pole in the manner described in point 1, above.
The speed of the re-alkalization process depends on the direct voltage which is applied, which is in turn dependent on the conductivity of the concrete and electrolyte, the density of the electrodes, and the distance between them. For normal building structures this voltage should be between 6-20 V, which will ensure that the re-alkalization is completed within a matter of days or weeks, depending on the overall conditions and the degree and depth of carbonation.
The method is illustrated in the enclosed drawings, where:
Fig. 1 shows a section through part of a concrete structure, where electricity is applied to the reinforcement in fresh and carbonated concrete, respectively, whilst Fig. 2 shows an equivalent section through a concrete structure where electricity is supplied by means of an external electrode in an electrolytic medium and part of the reinforcement in carbonated concrete.
The procedure will be described in more detail with reference the enclosed illustrations. In Fig. 1, there is a layer of reinforcement 1 in an area with carbonated concrete and a layer of reinforcement 2 is in fresh concrete. The reinforcement l is connected to one pole of a rectifier or battery 3, and the reinforcement 2 connected to the other pole. When the current is supplied the alkaline hydroxyl-ions migrate to the reinforcement 1 in the carbonated zone.
In Fig. 2, the reinforcement 4 is in a carbonated zone in the concrete. A suitable electrolytic medium 5 is applied to the surface of the structure. An electrode 6 has been located in this medium 5. The electrode 6 is connected to one pole of the battery or rectifier 7, whilst the reinforcement 4 in the carbonated zone is connected to the other pole. When the current is supplied, the alkaline hydroxyl-ions will migrate from an external medium 5 to the reinforcement 4 in the carbonated zone.
As a rule the polarity is selected so that the reinforcement in the carbonated concrete is connected to the negative pole of the battery. In special cases it could be an advantage to reverse the polarity (this is dependent on factors such as the type of salt in the electrolytic medium).
The external electrode is connected to one pole of the rectifier or battery, whilst the reinforcement in the carbonated zone is connected to the other pole in the manner described in point 1, above.
The speed of the re-alkalization process depends on the direct voltage which is applied, which is in turn dependent on the conductivity of the concrete and electrolyte, the density of the electrodes, and the distance between them. For normal building structures this voltage should be between 6-20 V, which will ensure that the re-alkalization is completed within a matter of days or weeks, depending on the overall conditions and the degree and depth of carbonation.
The method is illustrated in the enclosed drawings, where:
Fig. 1 shows a section through part of a concrete structure, where electricity is applied to the reinforcement in fresh and carbonated concrete, respectively, whilst Fig. 2 shows an equivalent section through a concrete structure where electricity is supplied by means of an external electrode in an electrolytic medium and part of the reinforcement in carbonated concrete.
The procedure will be described in more detail with reference the enclosed illustrations. In Fig. 1, there is a layer of reinforcement 1 in an area with carbonated concrete and a layer of reinforcement 2 is in fresh concrete. The reinforcement l is connected to one pole of a rectifier or battery 3, and the reinforcement 2 connected to the other pole. When the current is supplied the alkaline hydroxyl-ions migrate to the reinforcement 1 in the carbonated zone.
In Fig. 2, the reinforcement 4 is in a carbonated zone in the concrete. A suitable electrolytic medium 5 is applied to the surface of the structure. An electrode 6 has been located in this medium 5. The electrode 6 is connected to one pole of the battery or rectifier 7, whilst the reinforcement 4 in the carbonated zone is connected to the other pole. When the current is supplied, the alkaline hydroxyl-ions will migrate from an external medium 5 to the reinforcement 4 in the carbonated zone.
As a rule the polarity is selected so that the reinforcement in the carbonated concrete is connected to the negative pole of the battery. In special cases it could be an advantage to reverse the polarity (this is dependent on factors such as the type of salt in the electrolytic medium).
Claims (8)
1. The method of re-alkalizing a carbonated zone of a concrete structure from an adjacent zone of alkaline medium, wherein the carbonated zone has a pH
substantially below 12, which comprises, (a) applying between said zones a direct current voltage of at least six volts to effect a migration of alkaline ions from said alkaline medium to said carbonated zone, (b) generally maintaining said voltage until said carbonated zone reaches a pH of about 12, and (c) thereafter discontinuing the application of said voltage.
substantially below 12, which comprises, (a) applying between said zones a direct current voltage of at least six volts to effect a migration of alkaline ions from said alkaline medium to said carbonated zone, (b) generally maintaining said voltage until said carbonated zone reaches a pH of about 12, and (c) thereafter discontinuing the application of said voltage.
2. The method of claim 1, further characterized by said alkaline medium comprising non-carbonated zones of said concrete structure integral with and adjacent to said carbonated zones.
3. The method of claim 1, further characterized by said zone of alkaline medium comprising a mass of electrolytic medium applied to said structure, and said electrolytic medium being removed from said structure upon discontinuance of said applied voltage.
4. The method of claim 3, further characterized by said electrolytic medium comprising a material selected from the group consisting of concrete, mortar, cement grout and lime paste, said material being strongly retarded to prevent setting.
5. The method of Claim 3, further characterized by said electrolytic medium being adherently applied to said structure during the application of said voltage and being removed from the structure after discontinuance of said voltage.
6. The method of claim 1, further characterized by said direct current voltage being generally between 6 and 20 volts.
7. The method of claim 3, further characterized by said electrolytic medium comprising a material selected from the group consisting of calcium, sodium, potassium and their salts, said electrolytic medium being an aqueous solution in liquid form.
8. The method of claim 3, further characterized by said electrolytic medium comprising a material selected from the group consisting of calcium, sodium, potassium and their salts, said electrolytic medium being an aqueous solution absorbed in a porous medium.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP87902790A EP0264421B1 (en) | 1986-05-02 | 1987-04-30 | Electrochemical re-alkalization of concrete |
| PCT/NO1987/000030 WO1987006521A1 (en) | 1986-05-02 | 1987-04-30 | Electrochemical re-alkalization of concrete |
| JP63000159A JPH01176287A (en) | 1986-05-02 | 1988-01-05 | Electrochemical re-alkalinization method of concrete |
| US07/143,971 US4865702A (en) | 1986-05-02 | 1988-01-11 | Process of electrochemically re-alkalizing reinforced concrete |
| CA000590928A CA1337285C (en) | 1986-05-02 | 1989-02-13 | Electrochemical re-alkalization of concrete |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NO861737A NO160696C (en) | 1986-05-02 | 1986-05-02 | ELECTROCHEMICAL RE-ALKALINIZATION OF CONCRETE. |
| JP63000159A JPH01176287A (en) | 1986-05-02 | 1988-01-05 | Electrochemical re-alkalinization method of concrete |
| CA000590928A CA1337285C (en) | 1986-05-02 | 1989-02-13 | Electrochemical re-alkalization of concrete |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1337285C true CA1337285C (en) | 1995-10-10 |
Family
ID=44541475
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000590928A Expired - Lifetime CA1337285C (en) | 1986-05-02 | 1989-02-13 | Electrochemical re-alkalization of concrete |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1337285C (en) |
-
1989
- 1989-02-13 CA CA000590928A patent/CA1337285C/en not_active Expired - Lifetime
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4865702A (en) | Process of electrochemically re-alkalizing reinforced concrete | |
| US6022469A (en) | Repair of corroded reinforcement in concrete using sacrificial anodes | |
| US6303017B1 (en) | Cathodic protection of reinforced concrete | |
| EP1470266B1 (en) | Improvement in cathodic protection system | |
| EP0401519B1 (en) | Method for electrochemical treatment of porous building materials, particularly for drying and re-alkalization | |
| RU2110651C1 (en) | Concrete treating method | |
| US4832803A (en) | Removal of chlorides from concrete | |
| CN101412635B (en) | Electrochemical realkalization method for carbonizing reinforced concrete | |
| Velivasakis et al. | Chloride extraction and realkalization of reinforced concrete stop steel corrosion | |
| US6958116B1 (en) | Cathodic protection system | |
| US5366670A (en) | Method of imparting corrosion resistance to reinforcing steel in concrete structures | |
| CN201115981Y (en) | Electrochemistry rebasification device of carbonization steel reinforced concrete | |
| CN108867895A (en) | Distress in concrete blocking method | |
| CA1337285C (en) | Electrochemical re-alkalization of concrete | |
| CHESS | Corrosion in reinforced concrete structures | |
| JP4743814B2 (en) | Method for repairing concrete structure and repair liquid for concrete structure | |
| JP3449625B2 (en) | Repair method for neutralized concrete | |
| Unz | Insulating Properties of Cement Mortar Coating | |
| JPH0615792B2 (en) | Corrosion protection method for reinforcing bars in reinforced concrete structures and method for detecting corrosion state of reinforcing bars | |
| NO161454B (en) | ELECTROCHEMICAL RE-ALKALIZATION OF CONCRETE. | |
| AU682690B2 (en) | Realkalization and dechlorination of concrete by surface mounted electrochemical means | |
| RU2083773C1 (en) | Method for creating water-proofing coating on concrete surfaces | |
| BE1009152A5 (en) | Process for reinforcement corrosion'S AT WORK IN A MASS CONCRETE. | |
| WO1993021130A1 (en) | Method for inhibiting concrete cancer | |
| Kreilick | An Investigation of Electrochemical Techniques Designed to Mitigate the Corrosion of Steel in Historic Reinforced Concrete Structures: Frank Lloyd Wright's Freeman House, Hollywood, CA |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |