corrosion resistance of steel fibre reinforced · pdf filecorrosion resistance of steel fibre...

1 DTU Civil Engineering, Technical University of Denmark

Corrosion resistance of steel fibre reinforced structuresVictor Marcos Meson123, Gregor Fischer11 DTU, Department of Civil Engineering, Lyngby, Denmark2 COWI A/S, Tunnel Department, Lyngby, Denmark3 VIA Building, Energy & Environment, VIA University College, Horsens, Denmark

Workshop Instituto Eduardo Torroja, Madrid12/10/2016


Acknowledgements

• Supervision team• DTU: Gregor Fischer, Alexander Michel• COWI: Carola Edvardsen, Anders Solgaard• VIA UC: Torben Lund Skovhus

• Sponsors• DTU, COWI, VIA UC• InnovationsFonden, COWIfonden• VDS (Krampeharex, Arcelor‐Mittal, Bekært), Vejdirektoratet, Mapei

• Others• Students: Jakob Jensen, Oliver Thorpe, Simon Bozick, Viktor Balaz• DTU 3D Imaging centre: Carsten Gundlach


Contents

1.Introduction

2.Project description

3.Preliminary results

4.Summary


1. IntroductionBackground

Source: Solgaard A. (COWI)

Steel Fibre Reinforced Concrete is becoming an attractive solution for the industry:• Combined Reinforcement Systems• Total substitution of rebar by steel fibres

SFRC in compressed elements (Tunnel Linings)• Simplified production processes• Reduced cracking during handling and installation• Reduction of production failures (insufficient cover)

Restrictions on standards and general concernof SFRC structures under limits design aggressive exposures worldwide

Revision of Eurocode‐2 (Annex for SFRC)


1. IntroductionStatus and problem formulation

• RESEARCH durable under aggressive exposures (surface damage)• STANDARDS agreement allowing design for un‐cracked SFRC on SLS

Un‐cracked SFRC

•RESEARCH Disagreement regarding corrosion resistance for cracks < 0.30mm•Overall agreement on corrosion damage inside cracks > 0.30mm•Disagreement regarding corrosion damage inside cracks < 0.30mm

• STANDARDS Disagreement on crack limitation for aggressive exposures• SFRC allowed for small cracks or un‐cracked (SLS): TR‐63 (UK); ACI (US); AFTES (FR)•Design allowed with special provisions: EHE (ES); Testing; RILEM (FR)• Limitation for uncoated low‐carbon steel fibres: UNI (IT); CRN‐DT 204 (IT)•No consideration of fibres for structural verification: DBV/DafStb (DE); SFRC guidelines (DK)

•No mentioning of design restrictions: Fib‐Model code (FR)

Cracked SFRC


1. IntroductionStandards and guidelines

STANDARD CARBONATION CHLORIDES

Year ** XC2 XC3 XC4 XS2 XS3 XD2 XD3

ACI‐544‐1R‐96 (US)* 1996 ‐ ‐ wk<0.10 wk<0.10 wk<0.10 wk<0.10 wk<0.10

RILEM TC 162‐TDF (EU)* 2000 wk<0.30 wk<0.30 wk<0.30 Special Special Special Special

DBV‐Merkblatt Stahlfaserbeton (DE) 2001 wk<0.30Δh>20

wk<0.30Δh>20

wk<0.20Δh>25

wk<0.20Δh>40

wk<0.20Δh>40

wk<0.20Δh>40

wk<0.20Δh>40

UNI/CIS/SC4:2004 (IT) 2004 wk<0.30 wk<0.30 wk<0.30 wk<0.30 Coated wk<0.30 Coated

CNR‐DT 204/2006 (IT) 2006 wk<0.30Δh>10

wk<0.30Δh>10 Coated Coated Stainless wk<0.30

Δh>10 Coated

NZS 3101‐2:2006 (NZ) 2006 wk<0.30 wk<0.30 wk<0.30 wk<0.20 wk<0.20 wk<0.20 wk<0.20

TR‐63 (UK)* 2007 wk<0.30 wk<0.30 wk<0.30 wk<0.30 wk<0.30 wk<0.30 wk<0.30

EHE 2008 (ES) 2008 wk<0.30 wk<0.30 wk<0.30 Test Test Test Test

DAfStb Stahlfaserbeton (DE) 2012 wk<0.30 wk<0.30 wk<0.20 N/A N/A N/A N/A

Design guideline for structural applications of steel fibre reinforced concrete (DK) 2013 wk<0.30 wk<0.30 wk<0.20 N/A N/A N/A N/A

AFTES‐GT38R1A1 (FR) 2013 wk<0.20 wk<0.20 wk<0.20 wk<0.15 wk=0 wk<0.15 wk=0

SS‐812310:2014 (SE) 2014 wk<0.40 wk<0.40 wk<0.30 wk<0.20 wk<0.10 wk<0.20 wk<0.10

* Unclear/indefinite statements** EN 206 Exposure classes ✓ ✓ ? ? ? ??

Wk<0.30–0.40mm Wk<0.00–0.30mm / Not applicable / Special

Un‐cracked

• Accepted for all exposures• Durable under harsh environments

Hairline cracks(Wk < 200 µm)• Accepted for exposures: XC2‐3, XS1, XD1• Discussed for exposures: XC4; XS2‐3; XD2‐3

Medium cracks(200 < Wk < 400 µm)• Accepted for exposures: XC1‐2, XS1, XD1• Discussed for exposures: XC4; XS2‐3; XD2‐3

Large cracks(Wk > 400 ‐ 500 µm)• Out of SLS scope (e.g. tunnels)• Discussed for exposures: XC1

?

✓

x

!


1. IntroductionResearch• Chlorides (XD, XS)

• Abundant data• Large scatter• Many variables• Contradictions• Sufficient data?

• Carbonation (XC)• Limited data• Inconsistent conclusions• Data needed!

1977

, Bat

son

1977

, Mor

se19

78, R

ider

1987

, Man

gat

1990

, Kos

a19

98, W

eyde

rt19

99, B

alou

ch19

99, H

anse

n19

99, O

neil

2000

, Nem

egee

r20

04, B

erna

rd20

04, M

ante

gazz

a20

05, N

ords

trom

2008

, Ser

na20

09, R

oque

2011

, Bur

atti

2011

, Sun

2014

, Abb

as20

14, A

nand

an20

14, K

aufm

ann

2015

, Ber

nard

2015

, Tra

n

-50

050

c) Residual tensile strength

Stre

ngth

ratio

[%]

1975

, Han

nant

1977

, Bat

son

1977

, Mor

se19

78, R

ider

1985

, Sch

upac

k_AU

1985

, Sch

upac

k_BA

T19

85, S

chup

ack_

LI19

85, S

chup

ack_

WES

1987

, Kam

al19

87, M

anga

t19

90, K

osa

1998

, Wey

dert

1999

, Bal

ouch

1999

, Dha

nase

kar

1999

, Han

sen

1999

, One

il20

05, N

ords

trom

2006

, Gan

esan

2008

, Kop

ecks

ko20

08, S

erna

2009

, Gra

eff

2009

, Roq

ue20

09, S

anch

ez20

14, A

bbas

2014

, Kau

fman

n20

15, T

ran

020

6010

0

d) Corrosion damage

Cor

rosi

on d

amag

e [%

]

Chloride-induced corrosion (XD, XS)

1991

, Ker

n

1998

, Wey

dert

2000

, Nem

egee

r

2004

, Ber

nard

2005

, Nor

dstro

m

2014

, Kau

fman

n

2015

, Ber

nard

-40

040

c) Residual tensile strength

Stre

ngth

ratio

[%]

1975

, Han

nant

1985

, Sch

upac

k_AU

1987

, Kam

al

1991

, Ker

n

1998

, Wey

dert

2005

, Nor

dstro

m

2009

, San

chez

2014

, Kau

fman

n

020

4060

80

d) Corrosion damage

Cor

rosi

on d

amag

e [%

]

Carbonation-induced corrosion (XC)

Understand mechanisms involved in deterioration


1. IntroductionResearchPrincipal Component Analysis (PCA)• Orthogonal transformation to find correlations (Explain variance)

• Large scatter among studies• Inconsistent correlations

Variables• Exposure type, Age• Crack width• Quality (w/c, cement)• Fibre type, material, content• Temperature• Chloride, CO2

-2 0 2 4

-4

-2

0

2

4

a) scores

PC 1 (28.6%)

PC

2 (1

4.8%

)

2 4 6 8 10 12 14

0

1

2

3

4

b) Scree-plot: variances

Index

dat.1

PC

$var

-0.4 -0.2 0.0 0.2 0.4

-0.4

-0.2

0.0

0.2

c) loadings

PC 1 (28.6%)

PC

2 (1

4.8%

)

wc

f_strf_cont

exp_typ

tempcl

co2

crack

age

str_r

corr_d

bind

f_ld

crackT

??

!

□ Field ○ Lab

wc

f_co

atf_

str

f_co

ntex

p_ty

pte

mp cl

co2

crac

kag

est

r_r

corr

_dbi

nd f_ld

crac

kT

a) explained variance 2PCE

xpla

ined

var

ianc

e

0.0

0.2

0.4

0.6

0.8

1.0

wc

f_co

atf_

str

f_co

ntex

p_ty

pte

mp cl

co2

crac

kag

est

r_r

corr

_dbi

nd f_ld

crac

kT

b) explained variance 3PC

Exp

lain

ed v

aria

nce

0.0

0.2

0.4

0.6

0.8

1.0

wc

f_co

atf_

str

f_co

ntex

p_ty

pte

mp cl

co2

crac

kag

est

r_r

corr

_dbi

nd f_ld

crac

kT

c) explained variance 5PC

Exp

lain

ed v

aria

nce

0.0

0.2

0.4

0.6

0.8

1.0


1. IntroductionResearch• Mix‐design

• Unpractical binder contents, w/c ratios• Selection of fibre (steel‐concrete strength)• Evolution of fibre‐matrix bond

• Crack width• Inconsistent crack width (large dispersion)• Excessive/unpractical cracks (Wk > 0.5mm)

• Exposure• Short exposure periods (1‐3 months)• Uncontrolled conditions (temperature, solution)

• Specimens• Limited replicates (1‐5)• Inadequate analysis method

0

1

2

3

4

5

6

0 0.5 1 1.5 2 2.5 3 3.5 4

Stress (M

Pa)

CMOD (mm)

Initial

Reference

Gain

Loss

Brittle

[1]


1. IntroductionSummary

Carbonation ChloridesMildXC2‐3

AggressiveXC4

MildXS1‐2 / XD1‐2

AggressiveXS3 / XD3

Mixed‐in chlorides

Maximum water/binder ratio < 0.50 – 0.60 < 0.40 – 0.50 < 0.50 < 0.40 – 0.50

‐

Type of steel Low‐carbon Low‐carbon

Galvanized

Stainless

Low‐carbon Low‐carbon

Stainless

Critical crack width (mm) 0.30 – 0.50 0 – 0.30 0.20 – 0.30 0 – 0.20Sacrificial layer (mm) < 1 1 – 5 1 – 5 1 – 15Cracking / spalling No No No No YesCompressive strength loss None None None * Low – none MediumTensile strength loss None * Low – none None * Low – none HighResidual tensile strength loss

Un‐cracked Low – none Low – none Low – None Low – None

HighWide cracks (wk > 0.50 mm) Low High Medium High

Narrow cracks (wk < 0.50 mm) Low Medium Medium HighHairline cracks (wk < 0.20 mm) Low – none Medium – none Low – none Medium – none


2. Project descriptionAim and objectives

Aim • Evaluate the durability of SFRC for prefabricated tunnel lining segments exposed to corroding environments

Objectives• Characterise the design and service conditionsleading to steel fibre corrosion in cracked SFRC.

• Identify the mechanisms governing the deterioration of SFRC subjected to corrosive environments

• Quantify the impact of steel fibre corrosion on themechanical behaviour of SFRC.

Understand and update the background• Provide an updated background based on scientific andtechnical literature

• Provide a coherent basis explaining the existing limitsfound in the regulation

Produce consistent experimental data• Assess the durability of cracked SFRC and compare thedamage with traditional reinforced concrete

• Relate the damage observed on single fibres to thestructural effects on SFRC

Propose recommendations• Provide design recommendations for maximum allowed crack width and risk of corrosion propagation on SFRC

• Assist the development of future guidelines with updated knowledge and tools


2. Project descriptionExperimental programme

• Wet‐Dry cycles (2 years)• Combination of exposure and crack conditions• Post‐crack behaviour on bending and direct tension

Macro‐scale Experiments

• Single fibre pull‐out and x‐ray Micro‐CT (Micro‐Tomography)• Electrochemical testing on single fibres• Thin sections and microstructure analysis

Micro‐scale Experiments

• Deterioration model based on the Microscale study (fibre pull‐out)

• Validation with the data from the Macroscale study

Numerical Modelling

Conditions leading to fibre corrosion Understand and quantify fibre corrosionDamage in SFRC due to fibre corrosion

DESIGN STRATEGY

Macro StudyConditions

Micro StudyMechanisms

Modelling


2. Project descriptionMacro‐scale study

3‐Point Bending Test(EN 14651)

Load – DeflectionLoad ‐ CMOD

Source: EN 14651

Uniaxial Tension Test(Fischer. et al.)Load ‐ CMOD

Source [2]

AIMIdentify changes in the residual tensile strength

(toughness) after exposure

Deterioration


2. Project descriptionMacro‐scale study

Exposure method

• Wet-dry cycles (48h-cycle)

• 2 years (1-year, 2-year test)

• ≈9m3 total capacity (10 IBC tanks)

Amount of specimens

• 230 beams (150x150x600mm)

• 230 cubes (150mm)

• Total 3.8m3 (≈9 ton.)

Experiment variables

• Crack width: 150µm, 300µm

• Chloride exposure: 3.5%NaCl, 7.0%NaCl

• CO2 exposure: 0% CO2, 1% CO2

• Exposure time: 1-year, 2-year


2. Project descriptionMicro‐scale study

Source: [3]

Single‐fibre Pull‐out Test+

Micro X‐ray computed tomography

Linear Polarization Resistance+

Electrochemical Impedance Spectroscopy

Single fibre pull‐out tests+

Exposure


2. Project descriptionModelling

Regression analysis

Understand data from Macro‐scale experiments

Identify correlations based on a solid statistical approach

Multiple linear regression, ANOVA, t‐test…

Theoretical model

Relate deterioration mechanisms observed…•Crack shape and damage•Ingress of chlorides, leaching, carbonation…•Corrosion at fibres

To the mechanical behaviour•Fibre pull‐out•Uniaxial tension / Bending •Evolution of fibre‐matrix bond

Numerical analysis

Cohesive zone model of the fibre matrix interface during pull‐out

(Micromechanics)

Lattice / multiscale‐FEM model (Meso‐macro mechanics)

Analytical model


3. Preliminary resultsMacro‐scale studyCharacterization of crack propagation

• Digital Image Correlation (DIC)


3. Preliminary resultsMacro‐scale study


3. Preliminary resultsMacro‐scale study

Exposure method

• Wet-dry cycles (48h-cycle)

• 60 cubes (150mm)

• 5 replicates per group


• Crack width: 100µm, 200µm

• Chloride exposure: 7.0%NaCl

• Exposure time: 2 months

Observations

• Limited impact of exposure

• Large variability within groups

• Limited corrosion inside crack


3. Preliminary resultsMicro‐scale study

Description

• 120 pull-out cubes (70mm)

• 10 replicates per group

• Bond restoration on partially-pulled fibres


• Pull-out: 150µm, 300µm

• Limewater exposure Bond restoration

Observations

• Underestimation of bond stiffness (DIC)

• Error≈80µm Important under SLS!!

• Restoration of initial bond after healing0

100

200

300

400

0 0.5 1 1.5 2 2.5 3 3.5 4

Pull‐ou

t load [N]

Slip [mm]

Measured pull‐outTrue pull‐out (Aramis)Shifted pull‐out curve


2. Preliminary resultsMicro‐scale study

OriginalPull-out(300µm)

Damage

Damage at interface can be measured without invasive/destructive methods

OriginalPull-out(300µm)

Interfacial damage characterized by X-ray computed micro-tomography (µCT)• DTU 3D Imaging centre (Carsten Gundlach)• Resolution 45µm (ZEISS XRadia 410 Versa)


2. Preliminary resultsModelling

HEALING

DETETIORATION

DAMAG

E


4. Summary

• Discrepancies regarding durability of SFRC exposed to chlorides and carbonation limit the use of SFRC in civil infrastructure

• Former research does not focus on damage mechanisms and provides a limited explanation for the damage reported

• Multiscale investigation combines performance data (macro‐scale) with explanation of mechanisms (Micro‐scale) trough numerical modelling

• Preliminary Macro‐scale results show a large variability within same SFRC group and limited corrosion damage at short exposures

• Preliminary Micro‐scale results reveal underestimation of fibre‐matrix bond stiffness and show damage at fibre‐matrix interface during pull‐out


4. References[1] E. S. Bernard, “Age‐dependent changes in post‐crack performance of fibre reinforced shotcrete linings,” Tunn. Undergr. Sp. Technol., vol. 49, pp. 241–248, Jun. 2015.[2] I. Paegle, Characterization and modeling of fiber reinforced concrete for structural applications in beams and plates. 2015.[3] T. H. Ahn, D. J. Kim, and S. H. Kang, “Crack Self‐Healing Behavior of High Performance Fiber Reinforced Cement Composites Under Various Environmental Conditions,” in Earth and Space 2012, 2012, pp. 635–640.

S. Abbas, “Structural and Durability Performance of Precast Segmental Tunnel Linings,” University of Western Ontario, 2014.B. De Rivaz, “Durability issue for SFRC precast segment in tunnelling application,” in WUTC2010, 2010, pp. 1–10.R. Weydert and P. Schiessl, “Korrosion von Stahlfasern in gerissenem und ungerissenem Stahlfaserbeton. Abschlussbericht,” Bergisch Gladbach (Germany), 1998.D. J. Hannant and J. Edgington, “Durability of steel fibre concrete,” in Rilem Symposium 1975: Fibre reinforced cement and concrete, 1975, pp. 159–169.D. C. Morse and G. R. Williamson, “Corrosion behavior of steel fibrous concrete,” Dept. of Defense Dept. of the Army Corps of Engineers Construction Engineering Research Laboratory ;, Champaign Ill., 1977.P. S. Mangat and K. Gurusamy, “Corrosion resistance of steel fibres in concrete under marine exposure,” Cem. Concr. Res., vol. 18, no. 1, pp. 44–54, Jan. 1988.P. S. Mangat, “Long‐term properties of steel fibre reinforced marine concrete,” Mater. Struct. Matériaux Constr., vol. 20, no. 4, pp. 273–282, 1987.P. S. Mangat and K. Gurusamy, “Permissible crack widths in steel fibre reinforced marine concrete,” Mater. Struct., vol. 20, no. 5, pp. 338–347, Sep. 1987.K. Kosa and A. E. Naaman, “Corrosion of Steel Fiber Reinforced Concrete,” ACI Mater. J., vol. 87, no. 1, pp. 27–37, 1990.J.‐L. Granju and S. U. Balouch, “Corrosion of steel fibre reinforced concrete from the cracks,” Cem. Concr. Res., vol. 35, no. 3, pp. 572–577, Mar. 2005.D. Nemegeer, J. Vanbrabant, and H. Stang, “Final report on Durability of Steel Fibre Reinforced Concrete,” Copenhagen, Denmark, 2000.E. Nordström, “Durability of Sprayed Concrete Steel fibre corrosion in cracks,” Lulea University of Technology, 2005.R. Roque, N. Kim, B. Kim, and G. Lopp, “Durability of Fiber‐Reinforced Concrete in Florida Environments,” Florida, USA, 2009.E. S. Bernard, “Effect of Exposure on Post‐crack Performance of FRC for Tunnel Segments,” in SEE Tunnel:Promoting Tunneling in SEE Region ‐ ITA WTC 2015, 2015, p. 13.C. Frazão, A. Camões, J. Barros, and D. Gonçalves, “Durability of steel fiber reinforced self‐compacting concrete,” Constr. Build. Mater., vol. 80, no. 2015, pp. 155–166, Apr. 2015.E. S. Bernard, “Age‐dependent changes in post‐crack performance of fibre reinforced shotcrete linings,” Tunn. Undergr. Sp. Technol., vol. 49, pp. 241–248, Jun. 2015.E. S. Bernard, “Durability of cracked fibre reinforced shotcrete,” in Shotcrete: More Engineering Developments: Proceedings of the Second International Conference on Engineering Developments in Shotcrete, 2004, pp. 59–66.C. G. Berrocal, I. Löfgren, and K. Lundgren, “Experimental Investigation on Rebar Corrosion in Combination with Fibres,” in XXII Nordic Concrete Research Symposium, 2014, pp. 1–4.C. Dauberschmidt, “Untersuchungen zu den Korrosionsmechanismen von Stahlfasern in chloridhaltigem Beton,” Munich University, 2006.


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