Study on Ferritic Type Ss by Japan Society of Civil Engineers

8/6/2019 Study on Ferritic Type Ss by Japan Society of Civil Engineers

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Stainless Steel Bars

Stainless Steel BarsStainless Steel Bars

JAPAN SOCIETY OF CIVIL ENGINEERSJAPAN SOCIETY OF CIVIL ENGINEERS


2/31

Background of stainless steelBackground of stainless steel

barsbars Reinforcement corrosion in concrete due

to chloride ingress or carbonation is most

serious problem to reduce durability ofconcrete structures in Japan.

Countermeasure to reinforcementcorrosion: low W/C concrete concrete admixtures thick concrete cover surface protection epoxy-coated bars FRP reinforcement electrochemical corrosion control method

JIS for Stainless steel bars for concretereinforcement was established in 2008.



epoxy-coated bars

reinforcement corrosion


3/31

Type of stainless steelType of stainless steelStainless Steel Bars

SUS304 (18%Cr-8%Ni, ASTM:A276 304) Basic steel alloy most widely used as stainless

steel. SUS316 (16%Cr-10%Ni-2%Mo, ASTM:A276

316)

More corrosion-resistant steel alloy obtained byadding molybdenum to SUS304.

SUS410L (12%Cr-LowC, ASTM:A276 410L)

Chromium stainless steel with a controlled alloycontent.

Corrosion-resistance: SUS316 > SUS304 > SUS410



4/31

Tests on corrosionTests on corrosion--resistanceresistance

of stainless steel barsof stainless steel bars


Bare steel in solution Embedded in mortar

Embedded in concrete Exposed to actual corrosive

environment

Touching with different kind of metal

etc.



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Corrosion test in solutionCorrosion test in solutionStainless Steel Bars

Potentiostat Solution

ReferenceElectrode

ThermostaticTank (40deg)

Counterelectrode

Specimen

3 types of solutionsNo.1: pH9.1-9.7No.2: pH11.9-12.6No.3: pH13.2-13.4

Duration of test48hours corrosion criterion 0.5mA/cm2



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Results of corrosion test in solutionResults of corrosion test in solution

corroded not corroded

in 0.5% Cl- in 0%

conventional carbon steel


in 0.5% Cl- in 0% Cl-

stainless steel: SUS410L


pH 12.6


in 4.0% Cl- in 3.0% Cl-

stainless steel: SUS304


in 8.5% Cl- in 8.0% Cl-

stainless steel: SUS316


7/31

Corrosion criterion of chlorideCorrosion criterion of chloride

concentration in solutionconcentration in solution

0

2

4

6

8

10

1214

16

8 9 10 11 12 13 14 15pH

corrosionc

riteria(%) Carbon steelSUS410L

SUS304

SUS316



conventionalcarbon steel

stainless steel


8/31

Accelerated corrosion test in

concrete 40deg, 10 NaCl solution, 18.5months stainless steel bars: SUS304-SD, SUS316-SD, SUS410-SD

conventional carbon steel: SD295A bar diameter: D13 cover: 20mm concrete (W/C 50%)

10 NaCl

40

20mm

crack

10% NaCl solution 10% NaCl solution


specimen without crack specimen with crack



9/31

Results of acceleratedResults of accelerated

corrosion test in concretecorrosion test in concrete

stainless steel: SUS304-SD18.5months, crack width 0.18mm stainless steel: SUS316-SD18.5months, crack width 0.18mm

not corroded not corroded


not corrodedcorroded

stainless steel: SUS410-SD18.5months, crack width 0.18mm

conventional carbon steel3months, crack width 0.20mm

S i l S l B


10/31

0

5

10

15

20

25

0 5 10 15 20

duration time(months)

Con

centrations

ofchloride

ion

(kg/

m3)

SUS410L SUS316 SUS304

seawater

Chloride concentration inChloride concentration in

concrete during the testconcrete during the test



St i l St l B


11/31

Proposed durability design ofProposed durability design of

RC using stainless steel barsRC using stainless steel bars


Verification of corrosion resistance of RC structures by JSCEw < wa

w: crack width

wa: limit value of crack width

Cd< Clim

Cd: design value of chloride concentration at location of reinforcementClim: threshold value of chloride concentration for onset of corrosion


wCl-

reinforcement

chloride ingress

Chloride concentrationC(x,t)

xC

d

x

))2

1.0(1(0tD

cerfCC

d

dcld

=

St i l St l B


12/31

Limit value of crack width (Limit value of crack width (wwaa)) For conventional carbon steel reinforcement

For stainless steel reinforcement


Type ofreinforcement

Environmental conditions for reinforcement corrosion

Normal Corrosive Severely corrosiveDeformed bar

Prestressing steel

0.005c 0.004c 0.0035c

0.004c

c: cover < 100mm

Type of stainless steel Limit value of crack width

SUS304-SD

SUS316-SD

0.5mm

0.5mm

min (0.5mm, 0.005c)SUS410-SD

c: cover < 100mm




13/31


Threshold value of chloride concentrationThreshold value of chloride concentration

for onset of corrosion (for onset of corrosion (CClimlim))

1.2 kg/m3 is recommended for conventional carbonsteel reinforcement

Following values are recommended for stainless steelreinforcement


Type of stainless steelThreshold value of chloride concentrationfor onset of corrosion (kg/m3)

SUS304-SD 15

SUS316-SD 24

SUS410-SD 9



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Mechanical properties ofMechanical properties of

stainless steel reinforcementstainless steel reinforcement


strength fatigue strength

stress-strain curveYoung's modulus

thermal expansion coefficient




15/31

StressStress--strain curvesstrain curves

0

100

200

300

400

500

0 5000 10000 15000 20000

(10-6)

(N/mm

2)

D19

D25SD345D19

0

100

200

300

400

500

0 5000 10000 15000 20000

(10-6)

(N/mm

2)

D19

D25SD345D19

0

100

200

300

400

500

0 5000 10000 15000 20000

(10-6)

(N/mm

2)

D25D19

SD345(D19

0

100

200

300

400

500

0 5000 10000 15000 20000

(10-6)

(N/mm

2)

D25D19

SD345(D19)

similar with

conventional

strainhardening

strain (x10-6) strain (x10-6)

strain (x10-6)strain (x10-6)

stres

s(N/mm2)

stress

(N/mm2)

stres

s(N/mm2)

stress(

N/mm2)

SUS340 -SD SUS316 -SD

SUS410 SD295 SUS410 SD345





16/31

Strength and stressStrength and stress--strainstrain

model for designmodel for design Stress-strain model for stainless steel reinforcement

Definition of strength of stainless steel reinforcement

0

fyd

=Es

=fyd+Eu (-y )

y

0

fyd

= Es

= fyd

SUS410-SD295 except SUS410-SD295

0

fyk

0.2%

Es





17/31


Fatigue propertiesFatigue properties SUS304-SD, SUS316-SD: higher fatigue strength SUS410-SD: fatigue strength is close to estimated

by JSCE conventional design equation

100

150

200

250

300

350

400

0 500 1,000 1,500 2,000

N(103)

0(N/mm2)

SUS304-SD

SUS316-SD

SUS410-SD

100

150

200

250

300

350

0 500 1,000 1,500 2,000

N(103)

0(N/mm

2)

SUS304-SD


number of loading at fracture N (x103)

stressa

mplitude(N

/mm2)

JSCE eq.JSCE eq.

stressa

mplitude(N

/mm2)

JSCE equation can be used as well as conventional reinforcement.

s

ud

sp

k

a

srdfN

f

= 1

10190

s

ud

sp

k

a

srdfN

f

= 1

10190

number of loading at fracture N (x103)

D19 D35

T t i i f f RC



18/31

Test on seismic performance of RCmember using stainless steel

reversed cyclic loading test of

RC column specimen

-200

-150

-100

-50

0

50

100

150

200

-150 -100 -50 0 50 100 150

(mm)

N)

displacement (mm)

load(kN)

lateralreinforcement(SUS304, D13)

longitudinalreinforcement(SUS304, D25)

loading point





19/31


LCC assessment of RCLCC assessment of RC

structure using stainless barsstructure using stainless bars




20/31

Objective structure: piled pierObjective structure: piled pier

HWL

+2.36

LWL

+0.00

20.0

(unit: m)

super structure



C l l i di i


21/31

Calculation conditionCalculation condition

Service life t(year) 50 or 100

Concrete cover c(mm) 70

cement Ordinary Portland Cementconcrete

W/C 0.45

Reinforcement Conventional SUS410-SD SUS304-SD SUS316-SD

Climkg/m3 1.2 9 15 24

Ddcm2/year 1.46

Surface chloride C0kg/m3 9 or 13




22/31

Results: chloride concentration inResults: chloride concentration in

concreteconcrete In case that C0=13kg/m

3: conventional steel bars:

corroded in 10years SUS410-SD: corroded at

43years other stainless bars: not

corroded In case that C0=9kg/m

3: conventional steel bars:

corroded in 10years

stainless bars: not corroded

year

Chlor

ideconcentration(kg/m

3)

SUS410

conventional steel




23/31

Estimation of initial costEstimation of initial cost

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

N S-4 S-7 S-10

Conventional

Assumed material cost ofstainless steel

SUS304-SD: 7 times of

conventional steelSUS316-SD: 11 times of

conventional steelSUS410-SD: 4 times of

conventional steel

Calculated initial cost ofstructure

SUS304-SD: 1.3 times of

conventional structureSUS316-SD: 1.4 times of

conventional structure

SUS410-SD: 1.2 times ofconventional structure

SUS410-SD SUS304-SD SUS316-SD

Normalizedinitialcos

t


structures using stainless steel



24/31

Results of LCC assessmentResults of LCC assessment

CC00=9kg/m=9kg/m33

0

1

2

3

4

0 10 20 30 40 50 60

LCC

(

B-1(

B-2()S-4(SUS410)

S-7(SUS304)

S-10(SUS316)

100

B-1

B-2

C0=9kg/m3 S-4

year

Norm

alizedLCC

conventional steel +surface coating

conventional steel +electrochemical

corrosion protection

LCC of structuresusing stainless steel

SUS410-SD

LCC of structures using SUS304-SD, SUS316-SD, SUS410-SDare just equal to their Initial Cost because ofno corrosion.

Due to the maintenance cost, LCC of conventional structuresare higher than that of structures using stainless steel.

l f



25/31

Results of LCC assessmentResults of LCC assessment

CC00=13kg/m=13kg/m33

0

1

2

3

4

0 10 20 30 40 50 60

LCC

(

B-1(

B-2()S-4(SUS410)

S-7(SUS304)

S-10(SUS316)

100

B-1

B-2

S-4

C0=13kg/m3

year

Norm

alizedLCC

conventional steel +surface coating

conventional steel +electrochemical

corrosion protection

LCC of structuresusing stainless steel

SUS410-SD

LCC of structures using SUS304-SD, SUS316-SD are just equalto their Initial Cost because ofno corrosion.

Structure using SUS410-SD need to be repaired before 43 yeardue to reinforcement corrosion, which will affect its LCC.



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Examples of concrete structuresExamples of concrete structures

using stainless steelusing stainless steel

reinforcementreinforcement


LStainless Steel Bars


27/31

LeveeLevee


A i P f MA i P f t MStainless Steel Bars


28/31

Aomori Prefecture MuseumAomori Prefecture Museum


St tt b id (H K )St tt b id (H K )Stainless Steel Bars


29/31

Stone cutters bridge (Hong Kong)Stone cutters bridge (Hong Kong)

main tower(height: 298m)

cable-stayed bridge (span: 1018m)

2882 ton of stainless steel

reinforcements were used.

Design service life: 120years!




30/31

KouriKouri ohashiohashi bridge (Okinawa, Japan)bridge (Okinawa, Japan)


PC continuous box girder +PC rigid frame bridge (length:1960m), constructed in 2004

Stainless steel reinforcements

were adopted in wheel guardportion considering UV rayattack during construction.

severely corrosive environment,severe UV rays

Epoxy-coated reinforcementswere mainly adopted.

box girder segment


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Thank you for your kindThank you for your kind

attentionattention


Documents

Study on Ferritic Type Ss by Japan Society of Civil Engineers