EP1942240A2 - Verfahren zur Behandlung einer Betonstruktur und entsprechende Vorrichtung - Google Patents

Verfahren zur Behandlung einer Betonstruktur und entsprechende Vorrichtung Download PDF

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Publication number
EP1942240A2
EP1942240A2 EP07290018A EP07290018A EP1942240A2 EP 1942240 A2 EP1942240 A2 EP 1942240A2 EP 07290018 A EP07290018 A EP 07290018A EP 07290018 A EP07290018 A EP 07290018A EP 1942240 A2 EP1942240 A2 EP 1942240A2
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EP
European Patent Office
Prior art keywords
concrete structure
accessible surface
concrete
steel
steel reinforcement
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.)
Withdrawn
Application number
EP07290018A
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English (en)
French (fr)
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EP1942240A3 (de
Inventor
Marc-Henry Menard
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
M Lefevre
Original Assignee
M Lefevre
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by M Lefevre filed Critical M Lefevre
Publication of EP1942240A2 publication Critical patent/EP1942240A2/de
Publication of EP1942240A3 publication Critical patent/EP1942240A3/de
Withdrawn legal-status Critical Current

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    • 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
    • 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
    • E04G23/08—Wrecking of buildings

Definitions

  • the present invention relates to a method of treating a concrete structure, as well as the associated device.
  • the invention particularly relates to a method for extracting contaminant ions contained in the concrete and / or removing the contaminated concrete from the concrete structure.
  • steel is used to increase the tensile strength of the construction.
  • Concrete is not only resistant to compression but also protects the steel against corrosion thanks to the strongly alkaline environment that prevails in the concrete.
  • the alkalinity of the water contained in the pores of the concrete allows the formation of an oxide layer on the steel, the oxide layer constituting a barrier against corrosion.
  • the concrete coating that is to say the area between the surface in contact with the atmosphere and the first layer of reinforcement, can be degraded either by fire or any other physical cause, or by penetration of aggressive agents such as carbon dioxide which reduces the pH of the concrete, by a carbonation reaction. This has the effect of weakening the concrete construction and entails a risk of accident, especially in the case of buildings.
  • a first method of treating concrete consists in realcalinizing the carbonated zone, namely the coating and a small portion of the concrete located beyond the reinforcement, using an external electrolytic medium and a current electric capable of extracting anions from the carbonated zone.
  • the object of the invention is to improve the treatment of concrete, especially in terms of cost, nuisance and efficiency.
  • a method of treating a concrete structure comprising at least one accessible surface and at least one steel frame.
  • an electric field is applied between the steel frame and the accessible surface so as to cause migration of cations to the accessible surface and migration of anions to the steel frame.
  • the method uses a current flowing in the opposite direction to that used in the prior art.
  • the methods according to the prior art treat the concrete structures by migrating the anions to an external electrolytic medium and the cations to a steel frame.
  • the anions migrating towards the steel reinforcement increase the volume of the surface layer of the steel of the reinforcement, making it possible to detach at least a portion of the concrete structure situated between the accessible surface and steel frame, the rest of the concrete structure.
  • surface layer of the steel reinforcement is meant here the layer of material surrounding the steel of the reinforcement and comprising iron coming from said steel, for example rust.
  • the purpose of the method is to improve existing processes in which the degraded concrete coating in a reinforced concrete structure is removed and replaced with new concrete.
  • the method aims to improve the step of removing degraded concrete by exploiting the low tensile strength of concrete.
  • the increase in the volume of the surface layer of the steel reinforcement makes it possible to exert a tensile force on the embedding concrete, and thus to detach the part of the concrete situated between the surface of the concrete structure armed and steel frame.
  • the method allows in particular to detach the degraded concrete coating by limiting noise and damage to the rest of the concrete structure. Indeed, eliminations of concrete by percussion (jackhammer, chisel, ...) may cause more or less fine cracks in the rest of the concrete structure, which may weaken or require additional repair.
  • anions migrating to the steel frame can cause corrosion of the steel of the frame.
  • cations migrating to the accessible surface no longer have any effect limiting corrosion of the reinforcing steel.
  • Corrosion of a steel reinforcement can be achieved by circulating an electric current between this steel frame and an external electrode placed in electrical continuity with the surface of the concrete structure.
  • the direction of the current that allows this corrosion is such that the metal cations migrate to the surface of the concrete structure and the penetration of a liquid to the surface of the concrete is favored by electro-osmosis.
  • an external electrode is provided in electrical continuity with the accessible surface of the concrete structure and a tension is imposed between the steel reinforcement and the external electrode so as to circulate between the steel reinforcement and the electrode.
  • a current of value greater than 2 A / m 2 of steel reinforcement.
  • the reinforced concrete structure After detachment of the degraded coating, the reinforced concrete structure is treated by affixing a new coating. The structure can then recover its original geometric, mechanical and / or chemical characteristics.
  • the cations migrating towards the accessible surface comprise metal cations.
  • the metal cations may be cations degrading and / or contaminating the concrete structure.
  • the anions migrating to the steel reinforcement may be anions having an ability to limit the degradation of the concrete structure.
  • the method takes into account the contaminating cationic species.
  • a reverse current is applied here, in particular allowing extract the contaminating cations.
  • an external electrode is provided in electrical continuity with the accessible surface of the concrete structure and a tension is imposed between the steel reinforcement and the external electrode so as to circulate between the steel reinforcement and the electrode.
  • external a current value of less than 1 A / m 2 of steel reinforcement.
  • the method comprises a subsequent step during which the sign of the electric field between the steel reinforcement and the accessible surface is modified so as to cause a migration of cations towards the steel reinforcement.
  • the invention also relates to a treatment device of a concrete structure comprising at least one surface and at least one steel frame.
  • the device comprises a means for applying a potential intended to be arranged in electrical continuity with the accessible surface of the concrete structure and a power supply capable of circulating a current in the thickness of the concrete situated between the means of application of a potential and the steel frame, the negative terminal of the power supply being connected to the application means of a potential.
  • the means for applying a potential may comprise an external electrode and an electrolyte in contact with the external electrode and the accessible surface of the concrete structure so as to achieve electrical continuity between the external electrode and the surface. accessible from the concrete structure.
  • the external electrode plays the role of the cathode while the steel armature plays the role of the anode.
  • the electric field thus created between the external electrode and the steel frame makes it possible to migrate the cations towards the external electrode.
  • the electrolyte may comprise a solution containing anions that are corrosive with respect to the material of the steel reinforcement and capable of penetrating the concrete structure under the action of an electric field.
  • the solution may contain chloride anions that migrate to the reinforcement and promote corrosion of the steel.
  • the solution may also contain other anions.
  • the electrolyte may comprise a solution capable of collecting cations extracted from the concrete structure.
  • This embodiment relates to the extraction of contaminating cations from the concrete structure, but can also be applied to the first embodiment in which cations contained in the concrete structure are also extracted from the structure during processing.
  • the concrete structure 1 comprises concrete, a steel reinforcement 2 embedded in the concrete and an accessible surface 3.
  • a concrete region 4, called a coating situated between the accessible surface 3 and the steel reinforcement 2
  • a concrete region 5 situated on the opposite side to the concrete region 4 with respect to the steel reinforcement 2.
  • the concrete region 4 which may be partially or completely degraded, must be detached from the concrete structure 1 in order to replace it with a new concrete, or else to start the demolition of the structure 1.
  • the concrete structure 1 may be reinforced concrete, or even prestressed concrete.
  • the method is particularly applicable to prestressed concrete in which the steel with high mechanical strength and subjected to tensile stress, is insensitive to embrittlement by the nascent hydrogen.
  • an external electrode 6 is disposed on a portion of the accessible surface 3.
  • the external electrode 6 may consist of wires, cables, braids, trellis, plates, sheets, conductive plastics or all other conductive materials.
  • the external electrode 6 is placed in an electrolyte allowing making the electrical contact between the external electrode 6 and the accessible surface 3.
  • the electrolyte may comprise an aqueous solution of sodium nitrate, sodium chloride or the like.
  • the electrolyte will preferably be chosen so as to promote corrosion of the steel and to migrate easily under the effect of an electric field.
  • the electrolyte may be in liquid form, in the form of a gel, or even adsorbed in a porous medium such as rockwool, cellulose, sawdust, sand, clay or similar material.
  • the electrolyte can also be a concrete, a mortar, or a cement-based paste, provided that the setting of the cement is strongly retarded by a substance such as sugar.
  • the porous medium is chosen so as to allow the retention of the electrolyte without interfering with the operation of the treatment device of the concrete structure.
  • the external electrode 6 must be able to remain in contact with the accessible surface 3 even if parts of the concrete region 4 have already detached from the concrete structure 1.
  • the porous medium is for example a poultice 7 of plant fibers applied by projection.
  • the poultice 7 may in particular remain on the accessible surface 3 as a large part of the concrete region 4 remains attached to the concrete region 5 or to the steel frame 2. When the substantial portion of the concrete region 4 is detached, the poultice 7 comes off with it.
  • the external electrode 6 is placed in the poultice 7, so as to be electrically continuous with the accessible surface 3 via the electrolyte.
  • a power supply 8 (battery, generator or transformer connected to the general power grid) is used to circulate an electric current between the outer electrode 6 and the steel armature 2 which acts as an internal electrode.
  • the electrical supply 8 can be for example a current generator which circulates a current corresponding to a set value, by applying a sufficient voltage U between the external electrode 6 and the steel frame 2.
  • the current value may, for example, be greater than 2 A / m 2 of steel reinforcement.
  • “Steel reinforcement m 2” means the total area of the steel reinforcement in the treated zone, that is to say in the thickness of the concrete structure located opposite the external electrode .
  • the value of the current is chosen so as to favor the migration, toward said reinforcement, corroding species vis-à-vis the armature.
  • the power supply 8 may also be able to circulate, during the treatment time of the concrete structure, a modulated intensity current between the external electrode and the steel frame.
  • the external electrode 6 is electrically connected to the negative terminal of the power supply 8 and therefore constitutes the cathode, while the steel armature 2 is connected to the positive terminal of the power supply 8 and therefore constitutes the anode .
  • the anions migrate towards the steel reinforcement 2, the steel corrodes, and the cations contained in the concrete region 4 migrate towards the electrode 6. It is thus possible to concentrate near the steel reinforcement 2, the contaminating species likely to cause its corrosion.
  • the corroding steel of the reinforcement can increase the volume of its surface layer, for example rust, which causes stress in the concrete structure 1. These constraints are represented by arrows on the section top view of the concrete structure 1 shown in the figure 2 . The overall resultant of these stresses exerts a tensile force on the concrete regions 4 and 5.
  • the concrete region 4 may be partially contaminated with cations and possibly with anions, and must be treated.
  • the poultice 70 and the electrolyte used to collect the metal cations extracted from the concrete region 4 can be adapted to the types of metal cations; likewise, the value of the current flowing between the external electrode 6 and the steel frame 2 will be adapted according to the use.
  • the device for extracting the contaminating cations it is possible to apply, in a first step, the device for extracting the contaminating cations, then, in a second step, to reverse the direction of the current and to change the electrolyte used to treat the concrete structure by anion extraction 1 .
  • the device is first applied for a limited time to extract contaminating cations. It is possible to use a current generator 8 which, during the first step, circulates a current of value, for example less than 1 A / m 2 of steel reinforcement.
  • the aim here is to extract, during the first step, the contaminating cations while limiting the migration of the contaminating anions towards the steel reinforcement 2 in order to limit the duration of the second step.
  • the device facilitates the extraction of cations and / or the removal of a portion of a concrete structure, including a degraded concrete part.

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  • Engineering & Computer Science (AREA)
  • Architecture (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Mechanical Engineering (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Working Measures On Existing Buildindgs (AREA)
EP07290018A 2007-01-05 2007-01-08 Verfahren zur Behandlung einer Betonstruktur und entsprechende Vorrichtung Withdrawn EP1942240A3 (de)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR0752543 2007-01-05

Publications (2)

Publication Number Publication Date
EP1942240A2 true EP1942240A2 (de) 2008-07-09
EP1942240A3 EP1942240A3 (de) 2009-04-22

Family

ID=38268851

Family Applications (1)

Application Number Title Priority Date Filing Date
EP07290018A Withdrawn EP1942240A3 (de) 2007-01-05 2007-01-08 Verfahren zur Behandlung einer Betonstruktur und entsprechende Vorrichtung

Country Status (2)

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EP (1) EP1942240A3 (de)
MA (1) MA29656B1 (de)

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2239133A5 (en) * 1973-07-27 1975-02-21 Anvar Electrolytic concrete component demolition - by overlaying steel reinforcement with electrolysis products to cause swelling and split concrete
FR2588597B1 (fr) * 1985-10-10 1989-09-08 Quille Entreprise Procede et dispositif pour la demolition d'une paroi en beton contaminee et son application aux installations nucleaires
US6916411B2 (en) * 2002-02-22 2005-07-12 Lynntech, Inc. Method for electrically controlled demolition of concrete

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
"Corrosion of Steel in Concrete", 17 December 2003, WILEY-VCH VERLAG GMBH & CO. KGAA, Weinheim, FRG, ISBN: 978-3-52-730800-2, article LUCA BERTOLINI ET AL: "Corrosion of steel in concrete", pages: 329 - 343, XP055110177 *

Also Published As

Publication number Publication date
EP1942240A3 (de) 2009-04-22
MA29656B1 (fr) 2008-08-01

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