Lezing: Feasibility of externally bonded reinforcement for cathodic protection Philippe De Schoesitter Op uitnodiging van de Vereniging Adviseurs Beton Onderhoud en Reparatie (VABOR) VABOR bijeenkomst 22 maart 2012 Nebest Adviesgroep Mijdrecht - Nederland

Feasibility of externally bonded CFRP for cathodic protection PromotorenProf. dr. ir. S. Matthys, Prof. dr. ir. G. De Schutter BegeleidsterIr. D. Ertzibengoa Gaztelumendi Vakgroep Bouwkundige Constructies Voorzitter: prof. dr. ir. L. Taerwe Faculteit ingenieurswetenschappen en Architectuur Academiejaar Hoofdstuk 1: Corrosie van wapeningsstaal in beton en kathodische bescherming Hoofdstuk 2: Uitwendig verlijmde carbonvezelwapening (CFRP) Hoofdstuk 3: Experiment en toetsing haalbaarheid 22/03/20122 VABOR bijeenkomst - Philippe de Schoesitter

1. Corrosie en kathodische bescherming (ICCP) 22/03/20123 VABOR bijeenkomst - Philippe de Schoesitter 1.1 Corrosieproces en electrochemische achtergrond 1.2 Corrosiesnelheidsmeting 1.3 Kathodische bescherming: concrete toepassing

1.2 Corrosieproces 22/03/20124 VABOR bijeenkomst - Philippe de Schoesitter Fe 2+

22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 5 CriteriumCorrosion condition I corr <0,1 µA/cm²Passive condition I corr 0,1 to 0,5 µA/cm²Low to moderate I corr 0,5 to 0,1 µA/cm²Moderate to high I corr >1 µA/cm²High

1.2 Corrosiesnelheidsmeting 22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 6 Tafel-slope measurementLineaire polarisatie

 Mesh  Draad  Strip + coating (mortal, acryl…) Materials:  Metaal (Pt, Ti, Ag, Ni …)  Carbon (graphite …) 1.3 Kathodische bescherming concreet 22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 7 Cathodic Protection surface Anode BUtgb, Technische goedkeuring sector Burgerlijke bouwkunde, Kathodische bescherming door opgelegde stroom van wapening Volume resistivity < 1 Ω.cm Current density ca. 20 mA/m²

2. “CFRP EBR” 22/03/20128 VABOR bijeenkomst - Philippe de Schoesitter CFRP = Carbon Fibre Reinforced Polymer EBR = Externally bonded Reinforcement 2.1 Wat, hoe en waarom? 2.2 Mogelijkheid tot combinatie met K.B. -> geleidbaarheid van carbon -> overlap toepassingsgebied 2.3 Probleem: geleidbaarheid lijmmiddel

2.1 CFRP EBR 22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 9

2.1 CFRP EBR 22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 10

2.1 CFRP EBR 22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 11

Interesse in combinatie vanuit verschillende perspectieven:  CFRP EBR heeft positieve invloed op corrosie (zgn. “passieve bescherming”)  Sterke geleidbaarheid van carbonvezels: eis van 1Ω.cm ruimschoots voldaan  De toepassingsgebieden van aanbreng externe wapening en kathodische bescherming (of preventie) vertonen enige overlap. I.h.b. wanneer grote betonoppervlakken onder trekspanning extra wapening vergen 2.2 Toepassing van CFRP als anode-materiaal 22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 12

2.3 Geleidbaarheid epoxy-lijm Epoxy is insulative  conductive adhesive  additives in epoxy: - Metal - Carbon particles: >‘Carbon black’ (powder) >graphite (fibres) >nanotubes 22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 13

2.3 Geleidbaarheid epoxy-lijm: Carbon Black - small conductive particles - form a 3D-network as ‘electron path’ + tunnel effect - chemically rather inert, temperature resistant - “threshold concentration” - very high surface area (6 to 1500 m²/g) = problem! 22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 14 Coville NJ, Mhlanga SD, Nxumalo EN, Shaikjee A. A review of shaped carbon nanomaterials. S Afr J Sci. 2011;107(3/4), Art. #418, 15 pages. DOI: / sajs.v107i3/4.418

3. Experiment en toetsing haalbaarheid 3.1 Experiment set-up and program 3.2Results and discussion 3.3Conclusion 22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 15

3. Experiment en toetsing haalbaarheid 3.1 Experiment set-up and program 3.2Results and discussion 3.3Conclusion 22/03/2012VABOR bijeenkomst - Philippe de Schoesitter16

3.1 Experiment set-up and program 22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 17 Lollypop specimens: h=100mm, D≈50mm, reinforcement bar d=10mm Mortar composition:  C:SAND = 1:3  W/C = 0,65  Cl - /C = 4,25 wt% WET LAY-UP CFRP wraps: CP-ax-… : CFRP wraps axial fibre directions CP-rad-…: CFRP wraps radial fibre direction CP-…: wraps consists of epoxy adhesive only

22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 18 Primary anode: for connec- tion to DC power supply and current spread over anode surface Axial fibre direction: optimal current spread through fibres (expected), “Ax-…” specimens Radial fibre direction: worse current spread expected (bad conductivity of fibres in transversal direction), “Rad-…” specimens 3.1 Experiment set-up and program

22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 19 CP/immersion program Accelerated corrosion initiation and process:  initial chloride content (4,25wt%)  cyclic immersion in saline water (1wt%) CP program: phase 1: 14 days 58,35mA/m² phase 2: 14 days 26,53mA/m² 3.1 Experiment set-up and program

22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 20 Conductive epoxies: AdhesiveFiller Filler content (wt%) Bond strength [N/mm²] Resistivity [Ω.cm] Eccobond 50298Ni74-76>120,5 Eccobond 64CNi5,520,02 Eccobond 60L graphi te >1050 Eccobond 57 CAg>50<4,86x10 -4 ECC PC 5800 Carbo CB9,88(119,04) Epo-Tek 353NDCB12,97(78,72) 3.1 Experiment set-up and program

22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 21 Serial circuit  equal protection current! Separate baths  no current loss through water! 3.1 Experiment set-up and program

22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 22 Reference specimens: “Ref”: cyclic immersion but unprotected (CP) Ref-1,2,3: no CFRP wrap Ref-FRP: classic resistant CFRP wrap Tafel: not immersed, unprotected (CP) Tafel-ref: no wrap Tafel-50298: wrap 3.1 Experiment set-up and program

3. Experiment en toetsing haalbaarheid 3.1 Experiment set-up and program 3.2Results and discussion 3.3Conclusion 22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 23

22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 24 CP and Ref specimens  Linear Polarization (a) After 14 days CP/imm. (b) After 28 days CP/imm. CP switched off 48h in advance E corr ±20mV and 0,15mV/s Tafel specimens  Potentiodynamic meas. Tafel extrapolation for I corr Slope measurements for B Cell set-up 3.2 Results and discussion

22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter Results and discussion

22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter Results and discussion

22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter Results and discussion

22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter Results and discussion

22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 29 On average and compared to Ref specimens: AX-specimens:56% Rad-specimens:53% CP-specimens:64% 60L specimens:53% 57C specimens:71% 64C specimens:51% specimens:68% ECC specimens:61% Epo specimens:44% lower corrosion rates 3.2 Results and discussion

22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 30 I corr evolution: 3.2 Results and discussion

22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 31 Tafel slope measurements: B ≈ 26mV (depassivated steel) Good correlation with I corr from LP-measurements Mass loss measurements: Correlation with I corr from LP-measurements (within expected factor 2 error) 3.2 Results and discussion

22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 32 - The steel potentials are not found in the safe passive zone -> influence added chloride - I prot decrease (from 0,11 to 0,05mA) results in potential increase -> except: fibreless specimens - Active chloride corrosion initiation was not prevented, but ICCP was effective. -> influence added chloride -The radial fibre orientation gives the most consistent results. ->This overall improvement may be due to better concrete confinement -Anode resistivity: the most conductive epoxies show low change in I corr evolution between both measurements. ->fibres play no role in combination with very conductive epoxies -The CB added epoxies show the worst results. 3.2 Results and discussion

3. Experiment en toetsing haalbaarheid 3.1 Experiment set-up and program 3.2Results and discussion 3.3Conclusion 22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 33

22/03/2012 VABOR bijeenkomst - Philippe de Schoesitter 34 - CP was effective, CPrev was not obtained -Some improvements for further research: -Integration of reference electrodes ->Suspicion of fibre influence on polarization ->Depolarization measurements -No addition of Chlorides to the mortar and prolonged experiment to investigate Cprev -More specimens (for Tafel experiments and statistical certitude) -Further research on effects of conductive fillers on mechanical behaviour -Further research on integrating this addition in fabrication of prefab laminates 3.3 Conclusion