EP1777322A1 - Appareil et méthode pour la protection cathodique d'une structure en béton armé - Google Patents

Appareil et méthode pour la protection cathodique d'une structure en béton armé Download PDF

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Publication number
EP1777322A1
EP1777322A1 EP05077395A EP05077395A EP1777322A1 EP 1777322 A1 EP1777322 A1 EP 1777322A1 EP 05077395 A EP05077395 A EP 05077395A EP 05077395 A EP05077395 A EP 05077395A EP 1777322 A1 EP1777322 A1 EP 1777322A1
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EP
European Patent Office
Prior art keywords
current
concrete
steel
cathodic protection
approximately
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.)
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Application number
EP05077395A
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German (de)
English (en)
Inventor
Dessislava Atanassova Koleva
Jing Hu
Kees Van Beek
Klaas Van Breugel
Johannes Hendrik Wilhelmus De Wit
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.)
VAN DER HEIDE CATHODIC PROTECTION & CORROSION ENGI
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Technische Universiteit Delft
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Publication date
Application filed by Technische Universiteit Delft filed Critical Technische Universiteit Delft
Priority to EP05077395A priority Critical patent/EP1777322A1/fr
Publication of EP1777322A1 publication Critical patent/EP1777322A1/fr
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
    • C23F13/02—Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
    • C23F13/04—Controlling or regulating desired parameters
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F2201/00—Type of materials to be protected by cathodic protection
    • C23F2201/02—Concrete, e.g. reinforced

Definitions

  • the invention relates to an apparatus for cathodic protection of steel reinforced concrete structures, comprising an electrical source for generating an electrical signal, wherein the electrical source is provided with a first output terminal for connection with a cathode structure for contacting a steel segment of the reinforced concrete structure and with a second output terminal for connection with an anode structure for contacting a concrete surface of the concrete structure.
  • Corrosion prevention and protection techniques have been a focus of interest for decades in the field of civil engineering.
  • the corrosion of steel in concrete is essentially an electrochemical process, where at the anode iron is oxidized to iron ions that pass into the pore solution and at the cathode oxygen is reduced to hydroxyl (OH-) ions.
  • Anode and cathode form a short-circuited corrosion cell, with the flow of electrons in the steel and of ions in the pore solution of concrete.
  • Cathodic protection has been found to be a proven method and working technique to stop corrosion in reinforced concrete structures.
  • the polarization of the steel reinforcement is achieved by supplying impressed direct current to the steel embedded in concrete structures.
  • the repulsion of aggressive anions (e.g. chloride) which takes place along with the protection itself is a beneficial one as far as the corrosion risk of the steel is concerned.
  • cathodic protection is to artificially shift the potential of a metal so that it becomes either immune or passive.
  • a galvanic cell is set up by connecting the steel to a more reactive metal, usually zinc. The zinc then undergoes the anodic reaction and corrodes whilst the steel is rendered entirely unreactive because the whole surface undergoes the cathodic reaction and that the iron no longer dissolves.
  • the heterogeneities and instabilities inherent in the concrete material may lead to non-uniform distribution of the cathodic protection current and thus result in localized overprotected areas.
  • the overprotection current will result in alkali ions accumulation on the steel/rebar interface, thus causing softening of the C-S-H gel, possible alkali silica reaction (ASR) and loss of bond strength.
  • ASR alkali silica reaction
  • overprotection current will cause increased hydrogen evolution reactions on the steel surface and lead to hydrogen embrittlement in case of prestressed steel reinforcement.
  • ordinary impressed cathodic protection has been seldom applied to prestressed concrete structures.
  • cathodic protection current is found to induce structural deformations in the bulk concrete, inducing micro-cracking and unfavorable pore structure alterations.
  • main negative effects of cathodic protection comprise bond strength degradation, i.e. loss of adhesion at the steel/concrete interface, coarsening the pore structure and particularly in the interfacial transition zone (ITZ), thus yielding micro-cracks due to the current flow, alkali silica reaction (ASR) or hydrogen embrittlement of pre-stressed steel in concrete structures.
  • the invention aims at obtaining an apparatus for cathodic protection of steel reinforced concrete structures, wherein corrosion processes are counteracted while overprotection is avoided.
  • the electrical signal is a pulse shaped current and the electrical source is directly current controlled.
  • the above-mentioned sides effects of cathodic protection techniques are even further reduced, especially if the rise time of the pulsed current is larger than approximately 100 A/m 2 s.
  • the rise time of the pulsed electrical current is approximately 1000 A/ m 2 s.
  • other values are also applicable, such as 10.000 A/ m 2 s.
  • the negative side effects on the concrete bulk microstructure and/or on the steel/paste interface are lowered, thus reducing the extent of bond strength degradation that normally accompanies cathodic protection applications.
  • negative side effects on the concrete microstructure in terms of less detrimental effects on microstructural properties as porosity, pore size distribution and properties of the interfacial transition zone between paste and aggregate are lowered, the last being of significant importance for the electrolytic path in the system and for the manner of current distribution.
  • the research reveals higher effectiveness for the pulse cathodic protection in enhancing the aggressive (chloride) ion migration towards the anode (MMO titanium mesh used) and in reducing the aggressive ion concentration around the cathode (i.e. the steel bar under protection).
  • the pulse technique achieves sufficient steel polarization ( ⁇ -900 mV versus saturated calomel electrode (SCE) for the reinforced concrete) and initial terminal voltage with the same time constant (for the plain concrete) as the steady direct current approach.
  • SCE saturated calomel electrode
  • the use of a pulsed electrical signal is found to be less detrimental to the bulk concrete microstructure with respect to porosity, pore connectivity and micro-cracking.
  • an American patent publication US 5 324 405 discloses an apparatus for protecting metal structures such as pipelines or well casings in a conductive medium such as the ground.
  • a driving circuit provides a pulsed signal which is voltage controlled.
  • the apparatus according to the invention can be employed not only in the context of maintenance and/or repair of steel reinforced concrete structures, but also in the case of corrosion prevention of such structures.
  • the pulse cathodic protection can be applied in a more economic and less detrimental method compared to conventional impressed direct current techniques.
  • the apparatus according to the invention reduces side effects of cathodic protection techniques, it is also applicable to pre-stressed concrete. Further, it also addresses prevention, improved protection and better performance of reinforced concrete systems in terms of service life and durability issues.
  • the electrical pulsed current is periodic and has a duty cycle in the range between approximately 1% and approximately 50%.
  • the duty cycle is less than 25%, e.g. 12%.
  • a decrease of the duty cycle with 50% is compensated by doubling the current, so that the product of the pulse amplitude and the pulse duration remains approximately constant.
  • the invention relates to a method.
  • Figure 1 shows a schematic view of an apparatus 1 for cathodic protection of steel reinforced concrete structures according to the invention.
  • the apparatus comprises an electrical source 2, which can be implemented as a voltage or current source.
  • the electrical source 2 is provided with at least two output terminals, viz. a first, negative output terminal 3 which is connected with a cathode structure 4 and a second, positive output terminal 5 which is connected with an anode structure 6.
  • Figure 1 shows schematically a reinforced concrete structure 7, such as a part of a bridge or another civil engineering construction.
  • the structure 7 comprises steel rebars 8 which are at least partially embedded in concrete 9.
  • rebars 8 also other steel structures could be used, such as meshes.
  • the cathode structure 4 electrically contacts a steel rebar 8, while the anode structure 6 electrically contacts a concrete surface of the reinforced structure 7.
  • the electric source 2 During operation, the electric source 2 generates a pulsed electrical current which is fed to the output terminals 3, 5. As a consequence, the pulsed electrical current is impressed to the reinforced concrete structure 7 for protection purposes against corrosion effects.
  • the anode structure 4 connected to the positive terminal of the power supply, is chosen to be a relative non-reactive conductor such as carbon or titanium so that its corrosion rate is low.
  • the anode reaction then generates oxygen and acid (H + ) as follows: H 2 O ⁇ O 2 + 4H + + 4e -
  • the current densities normally encountered in cathode protection systems are sufficiently low for the amount of acid generated to be safely taken up by the normal alkalinity of the concrete.
  • the dominant corrosion products in the concrete structure protected by pulse cathodic protection are cotton-ball like goethite, as well as whiskey and delicate iron oxychlorides with a linear dimension of less than 5 ⁇ m.
  • a relatively compact and dense substrate composed of high-valent iron oxides hematite, maghemite and magnetite
  • iron oxychlorides of lamellar type are formed at 20 ⁇ m scale in the freely corroding concrete, which tend to induce cracking and promote the diffusion of chloride ions.
  • the favorable morphology e.g.
  • the electrical source is directly current controlled.
  • the current is adjusted to a predetermined current curve in dependence of a current measurement of the current that is generated by the electrical source 2.
  • the current generated by the electrical source 2 is substantially a periodic block signal with a rise time of approximately 10 mA/10 ⁇ s, or 1000 A/s. It is noted that the driving circuit disclosed in US '405 generates a current pulse with a much lower rise time, as the circuit is voltage controlled. As a consequence, the system disclosed in US '405 does not lead to the combination of counteracted corrosion processes while overprotection is avoided, anyway not in the extend of the apparatus according to the invention.
  • the frequency of the block signal is approximately 1 kHz. However, other frequencies could also be applied, e.g. in a range between approximately 100 Hz and approximately 100 kHz, such as 10 kHz. As indicated above, the quality of the rise time of the block signal is important for the desired effect of the apparatus according to the invention.
  • Figure 2 shows a graph with current pulse patterns as a function of time which are generated by the current controlled electrical source 2. All pulse patterns shown in Figure 2 are periodic having a frequency of (t 4 - t 0 ) -1 .
  • the pattern having a bold line 20 is a pulsed signal with a duty cycle of approximately 50%.
  • the pattern having a normal line 21 is a pulsed signal with a duty cycle of approximately 25%.
  • the amplitude of the latter signal is approximately twice the amplitude of the first signal, so that the delivered electrical energy per cycle remains substantially the same.
  • the pattern having a broken line 22 is a pulsed signal with a duty cycle of approximately 12.5%. Again, the latter signal has an amplitude which is approximately twice the amplitude of the second signal.
  • other duty cycles can be employed.
  • microstructural investigations have revealed favorable chemical composition and morphologies of the corrosion products and better concrete performance in the case of pulse regime.
  • the crystallinity, morphological aspects and spatial distribution of the corrosion and hydration products (characterized by quantitative image analysis on microlevel) provided supporting experimental evidences.
  • Figures 3 and 4 shows the difference of the conventional direct current approach ( Figure 3) and the pulsed current approach (Figure 4).
  • Figure 3 an interfacial transition zone under prior art conditions is shown as a SEM image with a magnification of 1000 x.
  • an enlarged gap, the interfacial transition zone 32 is visible between aggregate 30, such as sand or stone, and cement paste 31.
  • the enlarged gap is a side effect of the direct current applied to the concrete structure.
  • Figure 4 is also a SEM image with a magnification of 1000 x showing an interfacial transition zone.
  • the gap 42 between aggregate 40 and cement paste 43 belongs to a concrete structure that is treated with an apparatus according to the invention. The gap 42 is smaller, thus indicating that the method according to the invention has less side effects than the prior art method.
  • anode structure might contact the concrete structure by means of an external electrode e.g. as shown in Figure 1, or by means of an electrode embedded in the concrete structure.
EP05077395A 2005-10-18 2005-10-18 Appareil et méthode pour la protection cathodique d'une structure en béton armé Withdrawn EP1777322A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP05077395A EP1777322A1 (fr) 2005-10-18 2005-10-18 Appareil et méthode pour la protection cathodique d'une structure en béton armé

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP05077395A EP1777322A1 (fr) 2005-10-18 2005-10-18 Appareil et méthode pour la protection cathodique d'une structure en béton armé

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EP1777322A1 true EP1777322A1 (fr) 2007-04-25

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9353446B2 (en) 2013-04-29 2016-05-31 Transistor Devices, Inc. Systems and methods for impressed current cathodic protection
CN110333316A (zh) * 2019-07-16 2019-10-15 吴云 一种用于判断含板岩集料碱硅酸反应活性的混凝土微柱试件及其制备和使用方法
CN110376328A (zh) * 2019-07-16 2019-10-25 吴云 一种判断含板岩集料碱硅酸反应活性的方法
CN117805156A (zh) * 2024-02-27 2024-04-02 太原理工大学 对修复材料与基材之间界面过渡区水化程度的测试方法
CN117805156B (zh) * 2024-02-27 2024-05-10 太原理工大学 对修复材料与基材之间界面过渡区水化程度的测试方法

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3242064A (en) * 1960-02-29 1966-03-22 Engelhard Ind Inc Cathodic protection system
EP0448963A1 (fr) * 1990-02-26 1991-10-02 Nuova Polmet Cathodic Protection S.R.L. Dispositif de contrôle et de régulation automatique pour des systèmes de protection cathodique des structures en béton armÀ©
WO1992011399A1 (fr) * 1990-12-18 1992-07-09 Coating A.S. Procede pour la renovation d'ouvrages avec des elements metalliques inseres dans ces derniers
US5324405A (en) * 1991-09-09 1994-06-28 Doniguian Thaddeus M Pulse cathodic protection system
EP1063321A2 (fr) * 1999-06-17 2000-12-27 Gronvold & Karnov AS Améliorations dans la protection cathodique de structures en béton et de maçonnerie
DE10001706A1 (de) * 2000-01-18 2001-08-02 Citec Gmbh Vorrichtung und Verfahren zur Ansteuerung eines Elektrodensystems für die elektrochemische Sanierung von korrosionsgeschädigtem Stahlbeton
EP1241280A1 (fr) * 2001-03-12 2002-09-18 Cebelcor A.S.B.L. Procédé et installation pour la protection cathodique d'une structure métallique
US20030173231A1 (en) * 1999-09-15 2003-09-18 Ulrich Schneck Combination electrode for electrochemical restoration of corrosion-damaged reinforced concrete and method of controlling same

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3242064A (en) * 1960-02-29 1966-03-22 Engelhard Ind Inc Cathodic protection system
EP0448963A1 (fr) * 1990-02-26 1991-10-02 Nuova Polmet Cathodic Protection S.R.L. Dispositif de contrôle et de régulation automatique pour des systèmes de protection cathodique des structures en béton armÀ©
WO1992011399A1 (fr) * 1990-12-18 1992-07-09 Coating A.S. Procede pour la renovation d'ouvrages avec des elements metalliques inseres dans ces derniers
US5324405A (en) * 1991-09-09 1994-06-28 Doniguian Thaddeus M Pulse cathodic protection system
EP1063321A2 (fr) * 1999-06-17 2000-12-27 Gronvold & Karnov AS Améliorations dans la protection cathodique de structures en béton et de maçonnerie
US20030173231A1 (en) * 1999-09-15 2003-09-18 Ulrich Schneck Combination electrode for electrochemical restoration of corrosion-damaged reinforced concrete and method of controlling same
DE10001706A1 (de) * 2000-01-18 2001-08-02 Citec Gmbh Vorrichtung und Verfahren zur Ansteuerung eines Elektrodensystems für die elektrochemische Sanierung von korrosionsgeschädigtem Stahlbeton
EP1241280A1 (fr) * 2001-03-12 2002-09-18 Cebelcor A.S.B.L. Procédé et installation pour la protection cathodique d'une structure métallique

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9353446B2 (en) 2013-04-29 2016-05-31 Transistor Devices, Inc. Systems and methods for impressed current cathodic protection
CN110333316A (zh) * 2019-07-16 2019-10-15 吴云 一种用于判断含板岩集料碱硅酸反应活性的混凝土微柱试件及其制备和使用方法
CN110376328A (zh) * 2019-07-16 2019-10-25 吴云 一种判断含板岩集料碱硅酸反应活性的方法
CN117805156A (zh) * 2024-02-27 2024-04-02 太原理工大学 对修复材料与基材之间界面过渡区水化程度的测试方法
CN117805156B (zh) * 2024-02-27 2024-05-10 太原理工大学 对修复材料与基材之间界面过渡区水化程度的测试方法

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