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

5 DTU Civil Engineering, Technical University of Denmark

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

14 DTU Civil Engineering, Technical University of Denmark

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

15 DTU Civil Engineering, Technical University of Denmark

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

17 DTU Civil Engineering, Technical University of Denmark

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