2007d 3 servicelifedesign chloride attack

7/23/2019 2007d 3 ServiceLifeDesign Chloride Attack

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Concrete Materials, Mechanics &Engineering Lab., Yonsei Univ.

Service Life Design of Reinforced ConcreteStructures and its Verification-Chloride Attack

Service Life Design of Reinforced ConcreteService Life Design of Reinforced Concrete

Structures and its Verification Structures and its Verification - - ChlorideChloride

Attack Attack

Ha-Won SongProfessor

School of Civil and Environmental Engineering Yonsei Univ., Seoul 120-749, KOREA

Behavior of concrete




Introduction

Service life design of concrete structures

Durability concept and strategy

Performance-based durability design

Examples of service life design and verification

YongJong Grand Bridge

G-K fixed link project

Verification

Example of corrosion monitoring

Conclusion

Outline Outline




Old Codes: ACI, AASHTO, EC2,BS

Simple deemed-to-satisfy

rules (deterministic) Experience based rules of

thumb

Poor environmental classification

Result

No relation between performanceand service life (implicit 50 years)

Old Codes: ACI, AASHTO, EC2,BS

Simple deemed-to-satisfy

rules (deterministic) Experience based rules of

thumb

Poor environmental classification

Result

No relation between performanceand service life (implicit 50 years)

New Codes: Performance-based design

Degradation models

Material parameters

Detailing of environmental actions

Statistical quantification (mean, standarddeviation, distribution)

Choice of service life

New Codes: Performance-based design

Degradation models

Material parameters Detailing of environmental actions

Statistical quantification (mean, standarddeviation, distribution)

Choice of service life

Result

Documented service life design,

failure probability

Result

Documented service life design,

failure probability

Old and New Durability Concepts

ld and New Durability Concepts




Service life of RC structures ISO/WD 13823 ]

ervice life of RC structures ISO/WD 13823 ]

Time

Transfer mechanism

Resistance

mechanism (R)

Degradation Agents(moisture, Cl- , CO2 ,

micro cracks etc)

Damage or

disfigurementmechanism (Slim)

Degradation mechanism

ULS : R ≥ S? SLS : S ≤ Slim?

collapse malfunction

Durable Structure

Durabilitylimit state

Service lifets ≥td

Yes

texp

tstart

ts

Mass transport analysis

Environmental Actions(combination of

rain, de-icing salts etc)Boundary conditions

Corrosion of reinforcement

Concrete crack Deterioration of concrete

Structural analysis

t S = t start + t exp




Schematic description of service life design Schematic description of service life design

Time

S(t)

P f

Distribution of R(t)

R,S

Distribution of S(t)

R(t)

Service life density

Mean service life

Target Probability

of Failure P f

P {failure} at t D = P {t S ≤ t D } ≤

P target

t S = t start + t exp

P {failure} at t D = P {R(t D ) ≤ S(t D ) <0} < P target

t D : design service life




Measures:

High quality and impermeableconcrete

- low chloride diffusivity

(material)

- sufficient concrete cover

(design)

- no early-aged cracks(construction)

Performanced

based SLD

100 years of

service life

min cover

max. Dcl

Durability Design Strategy Durability Design Strategy




1 Selection of limit state

2 Selection of degradation model

3 Quantification of stochastic variables and analysis

Selection of cement type,

w/b-ratio, concrete mix

Determination of diffusion coefficient

Selection of relevant values of other model parameters

4 Repeated probabilistic analysis until acceptablefailure probability

Service Life Design Procedure Service Life Design Procedure ( ( DuraCrete DuraCrete procedure) procedure)




Corrosion initiationCorrosion init iation

1. Step: Selection of Limit state1. Step: Selection of Limit state

C c t C c r, ≥

Where :

c: Concrete cover

Ccr: Critical chloride concentration

Where :

c: Concrete cover

Ccr: Critical chloride concentration

Design for Chloride Induced Corrosion Design for Chloride Induced Corrosion Design for Chloride Induced Corrosion

environment

low corrosionrisk electro-

lytic process

impeded

not carbonated concrete

carbonated concrete

highcorrosion

risk

low corrosionrisk lack of

oxygen

~0.6 %

100 % r.h

constant

50 % r.h

constant

85 % r.h

changing

good quality

bad quality

Crit. Cl-/Cement




Where

t: Exposure period

x: Distance from surface

C

s

: Chloride surface concentration

D

0

: Chloride diffusion coefficient at t = t

0

t

0

: Reference period

n : Age factor

Where

t: Exposure period

x: Distance from surface

C

s

: Chloride surface concentration

D

0

: Chloride diffusion coefficient at t = t

0

t

0

: Reference period

n : Age factor

C x t C erf x

D ts

a

, = −

⎡

⎣

⎢

⎢

⎤

⎦

⎥

⎥

⎛

⎝

⎜

⎜

⎞

⎠

⎟

⎟

12

n

at

t D D ⎟

⎠

⎞⎜⎝

⎛ = 0

0

2. Step: Modelling of chloride ingress

based onFick ́s 2.law




|

|

|

⎠ ⎠

⎞

⎜

⎜

⎜

⎝ ⎝

⎛

⎥

⎥

⎦

⎤

⎢

⎢

⎣

⎡

−

aaDDtt22

xxerf erf 11ssCCttx,x,CC 0

n

0a Dckekt

tD ⎟ ⎠

⎞⎜⎝

⎛ = 0

n

0a Dckekt

tD ⎟ ⎠

⎞⎜⎝

⎛ =

3. Step: Quantification of stochastic variables3. Step: Quantification of stochastic variables

example: Bridgeexample: Bridge – – splash zonesplash zone

Parameter Parameter DimensionDimension Distr.Distr.--TypeType

xxcc Concrete cover Concrete cover mmmm 7575 88 Log normalLog normal

DD00 Chloride migrationChloride migration coef coef .. 1010--1212 mm22/s/s 6.56.5 1.31.3

NormalNormal

DeterministicDeterministic

NormalNormal

NormalNormal

Log normalLog normal

GammaGamma

0.600.60

0.40.4

0.920.92

1.01.0

4.04.0

0.07670.0767yearsyears

0.060.06

0.080.08

0.150.15

0.30.3

1.21.2

--

wt.wt.--%/binder %/binder

--

--

--

wt.wt.--%/binder %/binder

CCcr cr Critical chloride contentCritical chloride content

n Time factor n Time factor

kkee Factor, environmentFactor, environment

kkcc Factor , executionFactor , execution

CCss Chloride content at surfaceChloride content at surface

ttoo

Reference timeReference time

μ

σ

GammaGamma




4. Step: Probabilistic analysis until acceptable4. Step: Probabilistic analysis until acceptable probability of corrosion probability of corrosion

00

0.010.01

0.020.02

0.030.03

0.040.04

0.050.05

0.060.060.070.07

0.080.08

00 5050 100100 150150 200200Time [years]Time [years]

Probability of chlorideinduced corrosion




Determination of the design quality of the concrete Determination of the design quality of the concrete

The design surface chloride concentration: Cl

s

The background chloride concentration: Cl

0

The chloride diffusion coefficient: D

Cl

The critical chloride concentration: Cl

cr

The ageing factor: α




Service life prediction of RC structuresService life prediction of RC structures- - an example an example - - The 2 The 2 nd nd YongJong YongJong Grand Bridge project in Korea Grand Bridge project in Korea - -

65.315.3-0.19 Atmospheric

82.615.3-0.51Splash

10015.3-0.51Submerged

Relative humidity(%)

Temperature (℃ )CO2 concentration (ppm)Chloride concentration (mol/ℓ)Type of zones

Environmental conditions

Design life:

100 years.

Nominal end of service

life: corrosion initiation

Level of Reliability:

90% (β = 1.3)

Concrete pier and pylon




Process of Durability Design (Chloride attack) (1) Process of Durability Design (Chloride attack) (1)

Determine Statistical Property of Input Parameters for Chloride Model

Cs x Ccr k e,cl Do n etc…

Environment Property

Resistance Property





Monte Carlo Simulation (MCS) Analysis tool

Sampling from properties of variables

SAMPLES

(N: thenumber ofsimulation)

VARIABLE

n(N)D0(N)k e,cl(N)Ccr(N) X (N)Cs(N)

n(2)D0(2)k e,cl(2)Ccr(2) X (2)Cs(2)

n(1)D0(1)k e,cl(1)Ccr(1) X (1)Cs(1)

::::::

::::::

nD0k e,clCcr X Cs

n : (u,σ)D0 : (u,σ)

k e,cl : (u,σ)Ccr : (u,σ)

x : (u,σ

)Cs : (u,σ

)Property

(u: Mean

σ

: Standard dev.)




Estimation of the probability of failure !!

SAMPLES

(N: thenumber ofsimulation)

VARIABLE

n(N)D0(N)k e,cl(N)Ccr(N) X (N)Cs(N)

n(2)D0(2)k e,cl(2)Ccr(2) X (2)Cs(2)

n(1)D0(1)k e,cl(1)Ccr(1) X (1)Cs(1)

::::::

::::::

nD0k e,clCcr X Cs

⎥⎥⎦

⎤

⎢⎢⎣

⎡

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

⋅−=

t D

xerf C t xC sd

21),(

n

clet

t Dk D ⎟

⎠

⎞⎜⎝

⎛ = 0

0,





)()()( t S t Rt g −=

Environmental load [R(t)]

[ ] [ ]∑∑==

<−⋅=<⋅= N

j

N

j

f t S t R I N

t g I N

P11

0)()(10)(1

Resistance [S(t)]

Limit State Function

N: the number of simulation I[g(t)<0] : the indicator function

The estimation of the probability of failure

Process of DurabilityProcess of Durability Design(Chloride Design(Chloride attack)attack)

(4) (4)

designed chloride concentration [ Cd(x,t)]

critical chloride concentration [ Ccr]





R(t)

S(t)PF

target reliability index (β

=1.3, PF=10%)

Determine diffusion coefficient

)(1 F P−Φ−= β Reliability Index




Case for bridge at splash zoneCase for bridge at splash zone

Design for chloride induced corrosion Quantification of stochastic variables

Design for chloride induced corrosion Design for chloride induced corrosion Quantification of stochastic variablesQuantification of stochastic variables

|

|

|

⎠ ⎠

⎞

⎜

⎜

⎜

⎝ ⎝

⎛

⎥

⎥

⎦

⎤

⎢

⎢

⎣

⎡

−

aaDDtt22

xxerf erf 11ssCCttx,x,CC

-0.0767 yearReference timet0

-0.1wt.%/con’c wt.Initial chloride contentCi

0.150.92-Environment factorK e,cl

0.080.4- Age factorn

8.080.0mmConcrete cover depth X

1.24.0wt.%/con’c wt.Surface chloride contentCs

0.73.510-12

m2

/secchloride diffusion coeff.D0

Standard

DeviationMeanUnitProperty

n

a

D

cl

t

t

D ⎟

⎠

⎞⎜

⎝

⎛ =

n

a

D

cl

t

t

D ⎟

⎠

⎞⎜

⎝

⎛ =




Bridges Bridges at splash zone at splash zone

0

1

2

3

4

5

0 20 40 60 80 100

Time [years]

R e l i a b i l i

t y i n d e

Dcl=3.5x10-12 m2/s

Interrelation

chloride diffusion coefficient D

cl

age factor reliability

2.41.91.04 x10-12

2.52.11.33.5 x10-12

2.72.31.63 x10-12

3.32.82.32 x10-12

80

β(m2/s)(mm)

α = 0.6= 0.5= 0.4Max. D Cl-

Cover




0

1

2

3

4

5

0 20 40 60 80 100

Time [years]

R

e l i a b i l i t y i n d e

Dcl=11.5x10-12 m2/s

Bridges Bridges

2,72.21.212 x10-12

1.311.5 x10-12

1.411 x10-12

1.610 x10-12

>>2.7>>2.2

1.99 x10-12100

β

(m2/s)(mm)

α = 0.5= 0.4= 0.3Max. D Cl- Cover

Submerged ZoneSubmerged Zone

Interrelation chloride diffusion

coefficient D

cl

age factor

reliability




Bridges Bridges

Splash ZoneSplash Zone


coefficient D

cl

age factor

reliability

0

1

2

3

4

5

0 20 40 60 80 100

Time [years]

R e l i a b i l i t y i n d

e

Dcl=3.5x10-12 m2/s

2.41.91.04 x10-12

2.52.11.33.5 x10-12

2.72.31.63 x10-12

3.32.82.32 x10

-12

80

β(m2/s)(mm)

α = 0.6= 0.5= 0.4Max. D Cl- Cover




0

1

2

3

4

5

0 20 40 60 80 100

Time [years]

R

e l i a b i l i t y

i n d e x

Dcl=3.5x10-12 m2/s

Bridges Bridges

2.2

2.3

2.5

1.60.94 x10-12

1.81.33.5 x10-12

2.01.43 x10-12

3.02.52.02 x10-12

50

β(m2/s)(mm)

α = 0.60= 0.50= 0.40Max. D Cl-

Cover

Atmospheric Zone Atmospheric Zone


coefficient D

cl

age factor

reliability




Selected Durability Design Parameters

The 2nd YongJong Bridge

Below

-3.5

Above-3.5

Level

10011.5x10-12

Submerged

80Splash

50

3.5x10-12

Atmospheric

cover (mm)Max. Dcl- (m2/s)Exposure zone




Service life prediction of RC structuresService life prediction of RC structures- - an examplean example – – Busan Busan - - Geoje Geoje Fixed Link project in Korea Fixed Link project in Korea - -

I m m e r s e

d t u n n e l

Cable stayed bridgeCable stayed bridge

L=8.2 km



65.320.0670-Tunnel inside

65.315.3-0.19 Atmospheric

82.615.3-0.51Splash

10015.3-0.51Submerged

Relative humidity(%)Temperature (℃ )CO2 concentration (ppm)Chloride concentration (mol/ℓ)Type of zones

Environmental conditions

Design life:

100 years.

Nominal end of service

life: corrosion initiation

Level of Reliability:

90% (β

= 1.3)




0

1

2

3

4

5

0 20 40 60 80 100

Time [years]

R

e l i a b i l i t y i n

d e x

Dcl=6.0x10-12 m2/s

Design for i Design for i mmersed mmersed tunnel tunnel

2.11.36 x10-12

2.31.55 x10-12

2.71.94 x10-12

>> 2.1

3.12.43 x10-12

75

β(m2/s)(mm)

α = 0.60= 0.50= 0.40Max. D Cl-

Cover

Atmospheric Zone Atmospheric Zone


coefficient D

cl

age factor

reliability




0

2

4

6

8

10

0 20 40 60 80 100

Time [years]

R e l i a b i l i t y i n

d e x

Dcl=6.0x10-12 m2/s

3.32.86 x10-12

3.53.15 x10-12

3.83.44 x10-12

>> 3.3

4.23.83 x10-12

75

β(m2/s)(mm)

α = 0.50= 0.40= 0.30Max. D Cl-

Cover

Submerged ZoneSubmerged Zone


coefficient D

cl

age factor

reliability




Selected durability design parameters

Bridge

Below

-3.5

Above

-3.5

Level

756.5x10-12Submerged

75Splash

50

3.5x10-12

Atmospheric

cover

(mm)

Max. Dcl-

(m2/s)

Exposurezone

Sub-merged(outside)

756.0x10-12

Atmos-pheric

(inside)

cover

(mm)

Max. Dcl-

(m2/s)

Exposurezone

Tunnel

Possible mix proportions




Possible mix proportions

Specific gravity

· Coarse aggregate : 2.64 · Sand : 2.58

· Cement : 3.16 · Slag : 2.89

· Fly ash : 2.19 · Silica fume : 2.21

Air content : 4.0%

SubmergedTunnel

BridgeStructures

Area

102076576-1521521420.375T4

102077838-1701701420.375T3

102075180-1601601400.350T2

102076440-1801801400.350T1

102078272-1431431430.375B4

102076576-1521521420.375B3

1020797-11.41841841420.375B2

SP : 0.65~2.0%

AE : 0.014~0.023%

102075180-1601601400.350B1

FA SFSLAGOPC Admixture

G

(kg/m3)

S

(kg/m3)

Binder (kg/m3)W

(kg/m3)W/B

Verification of Service LifeVer cat on o Serv ce L e




Verification of Service Life Ver cat on o Serv ce L e

- - Scheme of Service Life Prediction Scheme of Service Life Prediction

Micro StructureDevelopment

Heat Generation Analysis

Early Age Behavior

Initiationperiod

time

Propagationperiod

Accelerationperiod

Deteriorationperiod

Loss of performance

related tocorrosion of

steel Time to corrosion

Time to corrosion cracking

Corrosion initiation Corrosion cracking

Corrosion cracking and service life of RC structure

W crit < W rust

Mixing PropertiesExposure Condition

•Weather•Temperature•Relative Humidity•Crack in Cover

Location of

Structures

Geometric Boundary

•Cement

• Aggregate

•Water

•Blend

Cement

C2SC3SC3 AC4 AF •Length

•Shape

•Boundary

FiniteElementMethod

Hygro Migration Analysis

Cl - Cl -

Cl -

Free chloride content

Total chloride content

critical

cl C

Chloride diffusion-penetration model

CO 2

CO 2

CO 2

CO2 Carbonation model

• pH distribution• Ca(OH)2 & CaCO3 distribution• Carbonation depth CO 2

pH = 9 pH = 12

Steel corrosion model

Corrosion current density(corrosion rate)

Corrosion product amount(rust)

Chloride content, pH

time

crack D eq

Crack model

• equivalent diffusion coefficient

• crack width




Verification result at atmospheric zone(1)

0.0

1.0

2.0

3.0

4.0

5.0

0 20 40 60 80 100 120

Concrete cover (mm)

C h l o r i d e c o n t e n t ( k g / m 3 )

0

0.3

0.6

0.9

1.2

1.5

0 50 100 150 200 250

Exposed time (year)

C h l o r i d e c o n

t e n t ( k g / m 3 )

1.2 Critical Cl -

content

Concrete cover = 50mm

Critical Cl -

content

Service life

[[ Atmospheric Atmospheric – – B1B1 ]]

0.0

1.0

2.0

3.0

4.0

5.0

0 20 40 60 80 100 120

Concrete cover (mm)


0

0.3

0.6

0.9

1.2

1.5

0 50 100 150 200

Exposed time (year)



Service life

0.0

1.0

2.0

3.0

4.0

5.0

0 20 40 60 80 100 120

Concrete cover (mm)

C h l o r i d e c o n

t e n t ( k g / m 3 )

0

0.3

0.6

0.9

1.2

1.5

0 50 100 150 200

Exposed time (year)



Service life




Summary of verification for service life

168 A-T-4178 A-T-3212 A-T-2 167 A-T-1

Immersed tunnel (inside)

132 A-B-4168 A-B-3162 A-B-2212 A-B-1

Bridge (Piers & Pylons)

Atmospheric Zone

Service Life (year)Mix TypeStructures Area

184S-T-4

143S-T-3

188S-T-2

152S-T-1

Immersed tunnel (outside)

171S-B-4

184S-B-3

165S-B-2

188S-B-1

Caissons (external)

Submerged Zone

176T-B-4

193T-B-3175T-B-2

180T-B-1

Pylons, Piers & CaissonsTidal and Splash Zone

Satisfy the designed service lifefor chloride attack

Comparison with Durability Evaluation by StandardComparison with Durability Evaluation by Standard




Comparison with Durability Evaluation by StandardComparison with Durability Evaluation by Standard

Specification of Korea and Japan Specification of Korea and Japan

iγ pγ

k φ

dC

limC

Equation for Durability Evaluation (Chloride attack)

Environmental factor (1.11)

Durability reduction factor (0.86)

designed chloride concentration (kg/m3)

Critical chloride concentration (1.2kg/m3)

designed chloride concentration (kg/m3)

Critical chloride concentration (1.2kg/m3)

structural coefficient(1.0 for general structures1.1 for important structures)

dC

limC

Korean Specification Japanese Specification

limk d p CCγ φ ≤ 1.0C

Cγ

lim

di ≤




Japanese Spec.Korean Spec.

18813916312194

10911295

152 A-T-4113 A-T-3132 A-T-298 A-T-1

Immersed tunnel (inside)

70 A-B-4

81 A-B-383 A-B-279 A-B-1

Bridge (Piers & Pylons)

Atmospheric Zone

Service Life (year)Mix TypeStructures Area

165

122

143

107

110

127130

111

147S-T-4

109S-T-3

128S-T-2

95S-T-1

Immersed tunnel (outside)

98S-B-4

114S-B-3117S-B-2

99S-B-1

Caissons (external)

Submerged Zone

106

122

125

106

95T-B-4

110T-B-3

113T-B-2

96T-B-1

Pylons, Piers & CaissonsTidal and Splash

Zone

SS




Summary Summary

An experience of performance based service life design for RCstructures subjected to chloride attack applied in major civilengineering projects in Korea is introduced. Selection of proper mix

proportions and verifying the design diffusion coefficients from the mixbefore construction are next critical tasks to complete the service life

design.-> e.g. Performance based evaluation of the service life .

New test method for diffusion coefficient

Sustainable construction of new concrete structures requires properservice life design and proper maintenance strategy which is getting

more important with increase of deteriorated concrete structures should be considered in design stage.

“Current balance in codes between structural design and durability is not good.

Durability is a design issue, and not just a material one . We possibly over-design

structurally and under-design for durability. Both over-design and under-designare undesirable.”

2007d 3 servicelifedesign chloride attack

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