Current Projects on Corrosion in FRC Materials and Structures at DTU Civil Engineering”
Corrosion Resistance of SFRC: a multi-scale approach to corrosion of crackedSFRC
Experimental investigations of the relation between damage at the concrete-steel interface and initiation of reinforcement corrosion in plain and fibre reinforced concrete: a experimental-numerical investigation of corrosion initation of rebars in SFRC and PC
2 DTU Civil Engineering, Technical University of Denmark
Corrosion resistance of steel Corrosion resistance of steel Corrosion resistance of steel Corrosion resistance of steel fibre reinforced structuresfibre reinforced structuresfibre reinforced structuresfibre reinforced structuresVictor Marcos MesonDTU, Department of Civil Engineering, Lyngby, Denmark
COWI A/S, Tunnel Department, Lyngby, Denmark
VIA Building, Energy & Environment, VIA University College, Horsens, Denmark
11/09/2017
3 DTU Civil Engineering, Technical University of Denmark
AcknowledgementsAcknowledgementsAcknowledgementsAcknowledgements
• Supervision teamSupervision teamSupervision teamSupervision team
• DTU: Gregor Fischer, Alexander Michel
• COWI: Carola Edvardsen, Anders Solgaard
• VIA UC: Torben Lund Skovhus
• SponsorsSponsorsSponsorsSponsors
• DTU, COWI, VIA UC
• InnovationsFonden, COWIfonden
• VDS (Krampeharex, Arcelor-Mittal, Bekært), Vejdirektoratet, Mapei
• OthersOthersOthersOthers
• DTU 3D Imaging centre: Carsten Gundlach
• NTNU: Tobias Danner, Klaarjte De Weerdt, Mette Geiker
• Students: Jakob Jensen, Oliver Thorpe, Simon Bozick, Viktor Balaz, Lisa Alm,
4 DTU Civil Engineering, Technical University of Denmark
1. Introduction1. Introduction1. Introduction1. IntroductionProject description
•Wet-Dry cycle exposure (2 years)
•Mechanics: bending and direct tension
•Fibre counting and chemical analysis
Macro-scale Experiments
• Conceptual deterioration model
• Statistical analysis
• Numerical model
Numerical Modelling
• Single fibre pull-out tests
• Electrochemical testing on single fibres
• Microstructure analysis
Micro-scale Experiments
Identify conditions leading to fibre corrosion
Understand and quantify fibre corrosion
Quantify damage in SFRC due to fibre corrosion
DESIGN STRATEGY
Disagreement in standards and research
Limited data available and large number of variables
Limited understanding of deterioration mechanisms
Corrosion of steel fibres in cracked concrete
Multi-scale investigation
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2. Macro2. Macro2. Macro2. Macro----scale experimentsscale experimentsscale experimentsscale experimentsExposure setup
Wet-dry cycle 4-days (48h wet + 48h dry)WET (2-days) DRY (2-days)
Carbonation
(Closed loop)
Wet – “7% NaCl”
Dry - (Air)
Wet – “Tap-water”
Dry - (1%v CO2)
Dry - (Air)Wet – “7% NaCl”
Dry - (1%v CO2)
Wet – “Tap-water”
Air dryer
(peltier cooler)
Exposure 1-2 years:- Limewater (dry cycle air)- 3.5% NaCl (dry cycle air)- 7.0% NaCl (dry cycle air)- Tap water (dry cycle CO2)- 3.5% NaCl (dry cycle CO2)
Experiment facts:400 specimens10 test-replicates
3-point bendingUniaxial tension
cracks:150 and 300 um
6 DTU Civil Engineering, Technical University of Denmark
2. Macro2. Macro2. Macro2. Macro----scale experimentsscale experimentsscale experimentsscale experimentsTesting process
Tested specimensFibre counting + Colour indicators
Chloride profiles (grinding)Mechanical testing
Load-CMOD law
Bending tests
FibreL=60 mm Ø=0.75 mm1900 MPa40 kg/m3
Concrete70MPa 56dw/b = 0.4Binder = 350 kg/m3
3-point bendingUniaxial Tension
7 DTU Civil Engineering, Technical University of Denmark
2. Macro2. Macro2. Macro2. Macro----scale experimentsscale experimentsscale experimentsscale experimentsMechanical testing
• Crack propagation Crack propagation Crack propagation Crack propagation Digital Image Correlation (DIC)
Original crack pathOriginal crack pathOriginal crack pathOriginal crack path
Additional cracksAdditional cracksAdditional cracksAdditional cracks
(after exposure)(after exposure)(after exposure)(after exposure)
8 DTU Civil Engineering, Technical University of Denmark
2. Macro2. Macro2. Macro2. Macro----scale experimentsscale experimentsscale experimentsscale experimentsNarrow cracks (300 µm) after 1 year
Lognormal dist.– Mean values
… Confidence intervals
-- Characteristic values
Reference 56-daysLab air 1-yearLimewater – Air3.5% NaCl – Air7.0% NaCl – AirTap water – CO2
3.5% NaCl – CO2
9 DTU Civil Engineering, Technical University of Denmark
2. Macro2. Macro2. Macro2. Macro----scale experimentsscale experimentsscale experimentsscale experiments7.0% NaCl exposure (1 year exposure) – S7C0A
pH > 8.3Free Cl- < 0.1 mol/L
AgNO3 0.1M Phenolphthalein
Major corrosion at surface (exposed fibres fully corroded)Severe corrosion at outer crack rimFull Chloride penetration inside crackCarbonate deposit inside crack (healing)5-10% of corroded fibres ruptured
Fibre counting● No corrosion● Light corr. (no cross-section loss)● Significant corr. (partial cross-section loss)● Critical corr. (total/critical cross-section loss)● Fibre fracture during pull-out
10 DTU Civil Engineering, Technical University of Denmark
3. Micro3. Micro3. Micro3. Micro----scale experimentsscale experimentsscale experimentsscale experimentsChemical analysis
Chloride mapping characterized by X-ray fluorescence spectroscopy (µXRF)
• NTNU (Tobias Danner)
11 DTU Civil Engineering, Technical University of Denmark
3. Micro3. Micro3. Micro3. Micro----scale experimentsscale experimentsscale experimentsscale experimentsTest description
Mechanical testingLoad-Slip law
Exposure (wetExposure (wetExposure (wetExposure (wet----dry cycles)dry cycles)dry cycles)dry cycles)
Epoxy coating
Plastic foil
Localized corrosion
Simulated crack exposure
Pre-pulled300µm
Displacement (x3)
Slip
Fibre
0000
50505050
100100100100
150150150150
200200200200
250250250250
300300300300
350350350350
0000 0.10.10.10.1 0.20.20.20.2 0.30.30.30.3 0.40.40.40.4 0.50.50.50.5
Fo
rce
(N
)F
orc
e (
N)
Fo
rce
(N
)F
orc
e (
N)
PullPullPullPull----out slip (mm)out slip (mm)out slip (mm)out slip (mm)
Extensometers
Cross-head
Challenges to measure pull-out slip accurately
Extensometers (x3)
Fibre
12 DTU Civil Engineering, Technical University of Denmark
3. Micro3. Micro3. Micro3. Micro----scale experimentsscale experimentsscale experimentsscale experimentsInterfacial damage at fibre-matrix
OriginalPull-out(300µm)
Damage
Damage at interface Damage at interface Damage at interface Damage at interface can be measured
without invasive/destructive methodswithout invasive/destructive methodswithout invasive/destructive methodswithout invasive/destructive methods
Interfacial damage characterized by X-ray computed micro-tomography (µCT)• DTU 3D Imaging centre (Carsten Gundlach)
Macro-cracksUniaxial tension test
Impact of cracks at microImpact of cracks at microImpact of cracks at microImpact of cracks at micro----scalescalescalescale
13 DTU Civil Engineering, Technical University of Denmark
4. Modelling4. Modelling4. Modelling4. ModellingConceptual deterioration model
HEALINGHEALINGHEALINGHEALING
DETETIORATIONDETETIORATIONDETETIORATIONDETETIORATION
DA
MA
GE
DA
MA
GE
DA
MA
GE
DA
MA
GE
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4. Summary4. Summary4. Summary4. Summary
• DiscrepanciesDiscrepanciesDiscrepanciesDiscrepancies regarding durability of SFRC durability of SFRC durability of SFRC durability of SFRC exposed to chlorides, carbonationchlorides, carbonationchlorides, carbonationchlorides, carbonationlimit the use of SFRC in civil infrastructureSFRC in civil infrastructureSFRC in civil infrastructureSFRC in civil infrastructure
• Limited data Limited data Limited data Limited data available hinders definite conclusions
• Former research does not focus does not focus does not focus does not focus on damage mechanisms damage mechanisms damage mechanisms damage mechanisms and provides a limited explanation limited explanation limited explanation limited explanation for the damage reported
• Overall performance and observations show limited corrosion damage limited corrosion damage limited corrosion damage limited corrosion damage and autogenous healing autogenous healing autogenous healing autogenous healing inside cracks
• Significant impact of healing of damage at fibredamage at fibredamage at fibredamage at fibre----matrix interface matrix interface matrix interface matrix interface at pull-out
Participation in committees: Eurocode TG2, ACI 544 and RILEM TC 262-SCI
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Experimental investigations of the relation Experimental investigations of the relation Experimental investigations of the relation Experimental investigations of the relation between damage at the concretebetween damage at the concretebetween damage at the concretebetween damage at the concrete----steel steel steel steel interface and initiation of reinforcement interface and initiation of reinforcement interface and initiation of reinforcement interface and initiation of reinforcement corrosion in plain and corrosion in plain and corrosion in plain and corrosion in plain and fibrefibrefibrefibre reinforced reinforced reinforced reinforced concreteconcreteconcreteconcreteA. Michel, A.O.S. Solgaard, B.J. Pease, M.R. Geiker, H. Stang, J.F. OlesenDTU, Department of Civil Engineering, Lyngby, Denmark
COWI A/S, Tunnel Department, Lyngby, Denmark
NTNU, Department of Structural Engineering, Trondheim, Norway
11/09/2017
16 DTU Civil Engineering, Technical University of Denmark
1. Experimental investigations1. Experimental investigations1. Experimental investigations1. Experimental investigations
Exposure in 3PBT
DIC to investigate interfacial damage Instrumented rebar for location and time
dependent potential and current measurements
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2. Numerical investigations2. Numerical investigations2. Numerical investigations2. Numerical investigations
Inverse analysis of 3PBTs• Cohesive law
• Fracture energy• Characteristic length
Development of FEM model• Slip at concrete-steel interface
• Separation at concrete-steel interface• Crack mouth opening displacement
18 DTU Civil Engineering, Technical University of Denmark
3. Results 3. Results 3. Results 3. Results –––– mechanical mechanical mechanical mechanical
Comparison of experimental observations obtained from DIC and numerical predictions• Load vs. CMOD• Load vs. slip and separation at concrete-steel interface
19 DTU Civil Engineering, Technical University of Denmark
3. Results 3. Results 3. Results 3. Results –––– mechanical and electrochemicalmechanical and electrochemicalmechanical and electrochemicalmechanical and electrochemical(a) location- and time-dependent potential, (b) corrosion current density (only for half of the sensors) measurements, and (c) simulated extent of slip and separation between concrete
and reinforcement for PC, SFRC (0.5 vol%), and SFRC (1.0 vol%)
CMOD 0.07 mm
CMOD 0.14 mm
CMOD 0.07 mm
20 DTU Civil Engineering, Technical University of Denmark
Thank you for your attention