DURABILITY of CONCRETE...

11

DURABILITYDURABILITY of of CONCRETECONCRETESTRUCTURESSTRUCTURES

PARTPART 33

Prof. Dr. Prof. Dr. Halit YAZICIHalit YAZICI

22

CARBONATIONCARBONATION& &

CORROSIONCORROSION

33

PROTECTIONPROTECTION of of STEELSTEEL FROMFROMCORROSIONCORROSION BYBY CONCRETECONCRETE

PHYSICALPHYSICAL PROTECTIONPROTECTIONPREVENTIONPREVENTION of of PENETRATIONPENETRATION of of WATERWATER & & HARMFULHARMFULMATERIALSMATERIALS toto STEELSTEEL ((DEPENDENTDEPENDENT on on IMPERMEABILITYIMPERMEABILITY & & THICKNESSTHICKNESS OF OF CONCRETECONCRETE COVERCOVER))

CHEMICALCHEMICAL PROTECTIONPROTECTIONPROVIDINGPROVIDING A A HIGHHIGH ALKALIALKALI ENVIRONMENTENVIRONMENT forfor STEELSTEEL((PASSIVIZATIONPASSIVIZATION EFFECTEFFECT -- ppHH ≅≅≅≅≅≅≅≅ 12.6 12.6 -- 13.513.5))

Concrete Reinforcement

steel

pH ≥≥≥≥ 12.5MICROSCOBIC OXIDE LAYER

(PASSIVE OUTER LAYER)

REINFORCEMENT CAN NOT CORRODE

(IF PASSIVE LAYER IS STABLE)

44

PROTECTIONPROTECTION of of STEELSTEEL FROMFROMCORROSIONCORROSION BYBY CONCRETECONCRETE

Concrete

Depassivation of Passive Layer

CARBONATION

pH < 9.5 –11.5

Steel Reinforcment

ACIDIC

WATERS

CHLORIDES

Cl- > CRITICAL VALUE

POSSIBILITY of CORROSION

(In Presence of Oxygen & Water)

End of Chemical Protection

INSUFFICIENT CHEMICAL & PHYSICAL PROTECTION

LEADS TO CORROSION of REINFORCEMENT

PERMEABLE & THIN CONCRETE COVERS ARE INADEQUATE

55

SOURCESSOURCES OF OF ALKALINITYALKALINITY

HYDRATION PRODUCTS of C3S & C2S Ca(OH)2

FREE CaO + H2O Ca(OH)2

(ALKALI OXIDE) K2O, Na2O + H2O KOH, NaOH

7

pH

Time

89

10

111213

14 ∼∼∼∼12.6

∼∼∼∼9.5∼∼∼∼8.3

1

2

3 4 5

Beginning of Alkalinity Protection2

Production of Concrete1

Beginning of Carbonation3

End of Chemical Protection4

Beginning of Electrolytic

Corrosion

5

66

Ca(OH)2

CO2

3Ca(OH)2+CO2 CaCO3+H2O

pH≈≈≈≈12.6 pH≈≈≈≈8.3

pH<9.5-11.5 Initiation of Corrosion(In Presence of O2 & H2O)

CARBONATIONCARBONATION

COCO22+ + HH22OO HH22COCO33 ((CARBONICCARBONIC ACIDACID))

SOSO22+ + HH22OO HH22SOSO33 ((SULFUROUSSULFUROUS ACIDACID))

PENETRATIONPENETRATION of of GASESGASES toto THETHE PORESPORES of of CONCRETECONCRETE & & REACTIONREACTION withwith POREPORE WATERWATER

NEUTRALIZATIONNEUTRALIZATION of of HYDRATEDHYDRATED COMPOUNDSCOMPOUNDS of of CEMENTCEMENT byby ACIDACID ATTACKATTACK

ACIDACID + + ALKALIALKALI SALT + SALT + WATERWATER

77

CARBONATIONCARBONATION

CHANGES in CONCRETE INNER STRUCTURECARBONATION of HYDRATED COMPOUNDS of CEMENTS

Ca(OH)2 , CSH, ETTRINGITE, FRIEDEL’S SALT

DROP of pH

VALUESHRINKAGE FORMATION

CORROSION of STEEL

(In presence O2 ve H2O )

MICROCRACKS on

CONCRETE SURFACE

88

FACTORSFACTORS INFLUENCINGINFLUENCINGCARBONATIONCARBONATION

CARBONATIONCARBONATION RATE;RATE;ALLALL FACTORSFACTORS INFLUENCINGINFLUENCING THETHE POROUSPOROUSSTRUCTURESTRUCTURE OF OF CONCRETECONCRETE(W/C, (W/C, CURINGCURING CONDITIONSCONDITIONS, , CEMENTCEMENT DOSAGEDOSAGE, , etcetc.).)

QUALITYQUALITY & & THICKNESSTHICKNESS OF OF CONCRETECONCRETE COVERCOVER((IMPERMEABILITYIMPERMEABILITY))

HUMIDITYHUMIDITY(50(50--70% 70% maxmax:):)

COCO22 CONTENTCONTENT((CLEANCLEAN AIRAIR 0.03% 0.03% -- POLLUTEDPOLLUTED 0.3%)0.3%)

CHEMICALCHEMICAL COMPOSITIONCOMPOSITION OF OF CEMENTCEMENT((ALKALIALKALI & & CaOCaO CONTENTCONTENT%)%)

TEMPERATURETEMPERATURE & & etcetc..

99

EFFECTEFFECT OF OF HUMIDITYHUMIDITY TOTOCARBONATIONCARBONATION & & RUSTINGRUSTING

Corrosion Risk

HUMIDDRY IMMERSED

Carbonation

Corrosion

CA

RB

ON

AT

ION

%50 %85

Relative Humidity (%)

50 85

RU

ST

ING

1010

FACTORSFACTORS INFLUENCINGINFLUENCINGCARBONATIONCARBONATION

FACTOR CARBONATION RATE

HUMIDITY % 50-70 MAX.

W/C RATIO

CURING PERIOD

CEMENT DOSAGE

DRYNESS OF CONCRETE

WATER SATURATION

CO2 CONCENTRATION

ALKALI CONTENT

COMPRESSIVE STRENGTH

TEMPERATURE (NORMAL)

1111

FACTORS INFLUENCING FACTORS INFLUENCING CARBONATION CARBONATION

tKC =C : CARBONATION DEPTH (mm)

K : COEFFICIENT of CARBONATION (mm/year0.5

t : TIME (year)

LOW STRENGTH LOW STRENGTH

CONCRETE W/C>0.6CONCRETE W/C>0.6K >3K >3--4 mm/year4 mm/year0.50.5

15 mm OF CARBONATION DEPTH CAN BE REACHED IN 15 YEARS!15 mm OF CARBONATION DEPTH CAN BE REACHED IN 15 YEARS!

CONCRETE COVERS (2CONCRETE COVERS (2--3 cm) MIGHT NOT PROVIDE THE NECESSARY 3 cm) MIGHT NOT PROVIDE THE NECESSARY

PROTECTION DURING SERVICE LIFEPROTECTION DURING SERVICE LIFE

28 g ün lü k b as ın ç da ya n ım ı(M pa )

K a rb o na t laşm a D erin liğ i(m m )

20 4540 1760 5

28 days comp. strength Carbonation depths

Depth of carbonation front of concrete specimens after 30 years Depth of carbonation front of concrete specimens after 30 years ( specimens are kept in open air unexposed to rain in England)( specimens are kept in open air unexposed to rain in England)

1212

CARBONATION of OTHER HYDRATED CARBONATION of OTHER HYDRATED COMPOUNDS of CEMENT BESIDES Ca(OH)COMPOUNDS of CEMENT BESIDES Ca(OH)22

CSH CSH CaCOCaCO33 , AMORF SILICATE , AMORF SILICATE

GEL, HGEL, H22OO

ETTRINGITEETTRINGITE CaCOCaCO33 , CaSO, CaSO44.2H.2H22O, O,

ALUMINIUM GEL, HALUMINIUM GEL, H22OO

FRIEDELFRIEDEL’’S SALTS SALT FORMATION of FREE FORMATION of FREE

ALUMINIUM GEL CHLORIDESALUMINIUM GEL CHLORIDES

CARBONATIONCARBONATION REACTION PRODUCTREACTION PRODUCT

1313

pH > 9.3

1 4 5 6 7 832 91 4 5 6 7 832 9

pH < 9.3

Carbonation

Front

Carbonated

concrete

CO2

Uncarbonated

concrete

SPRAY OF INDICATOR LIQUID SPRAY OF INDICATOR LIQUID

ON CORE SPECIMENON CORE SPECIMEN

PHENOLPTHALEIN (%0.1 )PHENOLPTHALEIN (%0.1 ) pH > 8.3pH > 8.3 PINKPINK, , RED RED COLORCOLOR

THYMOLPTHALEIN (%0.1 )THYMOLPTHALEIN (%0.1 ) pH > 9.3pH > 9.3 BLUE, BLUE, PURPLEPURPLE COLORCOLOR

THIS METHOD INDICATES THE THIS METHOD INDICATES THE

DEPTH OF CARBONATION DEPTH OF CARBONATION

FRONTFRONT

NORMAL CONCRETE with NORMAL CONCRETE with

HIGH pH VALUE REVEALS HIGH pH VALUE REVEALS

COLORCOLOR

CARBONATION FRONTCARBONATION FRONT

1414

CARBONATION FRONTCARBONATION FRONT

1515

REPLACEMENT OF CEMENT WITH LARGE AMOUNTS OF POZZOLANIC MATERIALS

CARBONATIONCARBONATION OF OF CEMENTCEMENT WITHWITHPOZZOLANICPOZZOLANIC ADDITIVESADDITIVES

STABILIZATION OF Ca(OH)2 BY POZZOLANIC REACTION

DECREASE IN AMOUNT OF CEMENT

SHARP DECREASES IN AMOUNT OF Ca(OH)2

INSUFFICIENT CURING

RAPID CARBONATION

1616

SCHMIDTSCHMIDT HAMMERHAMMER TEST ON TEST ON CARBONATEDCARBONATED SURFACESSURFACES

BIG ERRORS ON OLD STRUCTURES !!!

SURFACE HARDENINGCARBONATION

EXAMPLE:

TEST RESULTS OF TWO BUILDINGS

(a. 25 YEARS OLD b. 50 DAYS OLD)

HAMMER RESULTS : fck = 16.9 MPa !

CORE RESULTS : fck = 4.8 MPa

AGE OF CONCRETE 25 YEARS

HAMMER RESULTS : fck = 25.1 MPa !

CORE RESULTS : fck = 18.0 MPa

AGE OF CONCRETE 50 DAYS

1717

REALKANIZATIONREALKANIZATION

APPLICATION of LIME BASEDPLASTER

ALKALINITY of PORE WATERINCREASES by PENETRATIONOF Ca++ ve (OH)- IONS in WATER

LOSS OF EFFECTIVENESSDURING DRYING !!

PLACEMENT of TITANIUMANOD ON CONCRETESURFACE

NOT PRACTICAL+

SIDE EFFECTS;RISK OF HYDROGENBRITTLENESS of R.F., ASR, LOSS OF BOND

PENETRATION of Na+ & (OH)-

IONS BY APPLICATION of DIRECT CURRENT

•CARBONATED SURFACES SHOULD BE SCRAPED OFF IF POSSIBLE.

•SURFACES SHOULD BE REPAIRED by SPECIAL MORTARS.

•IMPERMEABILITY SHOULD BE PROVIDED

LOW W/C, min. 20 mm THICKNESS, HIGH LIMECONTENT

ACTIVE METHODS PASSIVE METHODS

18

DEVELOPMENT of CORROSIONC

orr

osi

on

Initial stage Active corrosion

Service life

Acceptable level

PENETRATION of CHLORIDES, CARBONATION FRONT, WATER, OXYGEN to INNERLAYERS of RFC must be PREVENTED

IMPERMEABLECONCRETE COVER withSUFFICIENT THICKNESSis NECESSARY

EXTRA EXPENSIVEPRECAUTIONS MIGHT BE REQUIRED (VERY SELDOM)

19

CORROSION

QUALITY of CONCRETE COVER is the MAIN FACTOR of DURABILITY

APPLICATION MISTAKES ⇒⇒⇒⇒ FORMATION of CRACKS over TOP SURFACES

BLEEDING & PLASTIC SETTLEMENT ⇒⇒⇒⇒ EXCESS WATER on top SURFACES (HIGH W/C RATIO)

RAPID EVAPORATION ⇒⇒⇒⇒ PLASTIC SHRINKAGE CRACKS

POOR CURING ⇒⇒⇒⇒ RETARDATION of HYDRATION RATE ⇒⇒⇒⇒ LOWMECHANICAL PROPERTIES ⇒⇒⇒⇒ CRACKS

MORE PERMEABLE CONCRETE COVER THAN THE

CONCRETE CORE

2020

CORROSIONCORROSION OF OF STEELSTEEL

FeFe + + ½½OO22++HH22OO FeFe(OH)(OH)22

BASICALLYBASICALLY IS A IS A RETURNINGRETURNING TOTO ORIGINALORIGINAL FORMFORM

-- ATMOSPHERICATMOSPHERIC

-- ELECTROLYTICELECTROLYTIC

-- CHLORIDECHLORIDE

-- CONTACTCONTACT

ATMOSPHERICATMOSPHERIC CORROSIONCORROSION

FeFe (OH)(OH)22 FeOFeO + + HH22OO

RUST

-- HYDROGENHYDROGEN BRITTLENESSBRITTLENESS

CORROSIONCORROSION RATE RATE ((DEPENDSDEPENDS ON ON HUMIDITYHUMIDITY))

ClearClear AtmosphericAtmospheric ((climaticclimatic) ) ConditionsConditions 44--6 6 µµµµµµµµm/m/yearyear

PollutedPolluted AtmosphericAtmospheric conditionsconditions100100--1000 1000 µµµµµµµµm/m/yyearear

IFIF RUSTRUST LAYERLAYER IS IS STABLESTABLE⇒⇒⇒⇒⇒⇒⇒⇒ NOT NOT DANGEROUSDANGEROUS

IFIF NOT NOT STABLESTABLE ⇒⇒⇒⇒⇒⇒⇒⇒ MEASUREMENTMEASUREMENT OF OF DIAMETERDIAMETER, , TENSILETENSILE STRENGTHSTRENGTH TEST, TEST, CLEANINGCLEANING IS IS NECESSARYNECESSARY

TYPESTYPESOF OF CORROSIONCORROSION

2121

ELECTROELECTRO--CHEMICALCHEMICAL CORROSIONCORROSION of of METALSMETALS

DISSOLUTION of IRON

IONIZATION of STEEL byLOSS OF ELECTRONS

Fe ⇒⇒⇒⇒ Fe2+ + 2e-

LOSS of MASS

TWO SIMULTANEOUS REACTIONS THAT COMPLIES EACH OTHER

OXIDATION(ANODIC PROCESS)

COMBINATION of SURPLUSELECTRONS in STEEL + H2O + O2 FORMS 2(OH)-

2e- + ½O2 + H2O ⇒⇒⇒⇒ 2(OH)-

PROTECTED

TRANSFER OF e- TO CATHODE

ANODIC & CATHODIC AREAS MAY BE VERY CLOSE TOEACH OTHER (MICROELEMENT) OR MAY BE FAR AWAY (MACROELEMENT) IN THE SAME STEEL.

REDUCTION(CATHODIC PROCESS)

TRANSFER OF (OH)- TO ANODE

2222

ELECTROELECTRO--CHEMICALCHEMICAL CORROSIONCORROSION of of METALSMETALS

CONCRETE PORE WATER: PROVIDES AN ELECTROLYTE MEDIA (THAT ENABLES THETRANSFER OF ELECTRONS)

BATTERY FORMATION

CATHODIC & ANODIC PROCESSES BEGINS

FACTORS

HUMIDITY,

O2 CONCENTRATION,

SALT CONCENTRATION,

THICKNESS & IMPERMEABILITY of CONCRETE

DIFFERENT ANODIC & CATHODIC AREAS

2323

CORROSIONCORROSION OF OF STEELSTEEL

HH22OO

OO22

½½OO222(OH)2(OH)--FeFe+2+2

2e2e--

Anodic Cathodic

Steel

Concrete Porewater

(Electrolythic)

ANODICANODIC PROCESSPROCESS

FeFe FeFe+2+2 + + 2e2e--

CATHODICCATHODIC PROCESSPROCESS

HH22OO +1/+1/2O2O22 + + 2e2e-- 2(OH)2(OH)--

FeFe(OH)(OH)22+ + HH22OO+ 1/+ 1/2O2O22 FeFe(OH)(OH)33

Oxygen diffusionthrough concrete cover

FeFe(OH)(OH)22Fe+2 + 2(OH) -

2424

CHLORIDECHLORIDE CORROSIONCORROSIONCHLORIDE IONS:

MOST HAZARDOUS CHEMICAL FOR REINFORCEMENT

DISSOLUTION OF PASSIVE LAYER

INCREASE OF ELECTROLYTE, DECREASE ELECTRICALRESISTANCE, EASE OF ION FLOW

REDUCTION OF pH value

CONCRETECONCRETE MATERIALSMATERIALS((CEMENTCEMENT, , WATERWATER, , ADDITIVESADDITIVES, , AGGREGATEAGGREGATE))

INTRUSIONINTRUSION of of EXTERIOREXTERIORCHLORIDESCHLORIDES((SEASEA WATERWATER, DE, DE--ICINGICING SALTSSALTS, , ETCETC.).)

CHLORIDECHLORIDESOURCESSOURCES

2525

CHLORIDECHLORIDE SOURCESSOURCESSALT PLANTS

USAGE OF SEA WATER FOR CONCRETEMIXING AND/OR CURING WATER

SALTY AGGREGATES

(SAND PROCURED FROM SEA)

CONTACT WITH SEA WATER & WETTING

– DRYING CYCLES

DE-ICING AGENTS

SALTY UNDERGROUND WATER

WINDS BLOWING FROM SEA

ACCELERATORS WITH CaCl2

2626

INTRUSIONINTRUSION OF OF CHLORIDECHLORIDE IONSIONS TOTOCONCRETECONCRETE

WETTING

-DRYINGPENETRATION

of Cl-Cracks0.05

25

40

60

Content (%)

Pen

etre

tion

dep

thfr

om

surf

ace

(mm

)

0.10 0.15 0.20 0.25 0.30

80

CAPILLARY SUCTION OF SALINE WATER, DIFFUSION PERIODS, WETTING-DRYING CYCLES

INCREASE Cl- CONCENTRATION & Cl- PENETRATION DEPTH

2727

CHLORIDECHLORIDE CORROSIONCORROSION

(OH)-Cl -

Fe +3pH≈≈≈≈5

Fe Cathode

Passive Layer

(∼50 µm)

pH>12.5

Electrolyte

AnodeSteel

FeClFeCl33FeFe+3+3 + + 3Cl3Cl--ElectrolyteElectrolyte

FeClFeCl33 + 3(OH)+ 3(OH)--ElectrolyteElectrolyte

FeFe(OH)(OH)33 + + 3Cl3Cl--

REGENERATIONREGENERATION of of CLCL-- ⇒⇒⇒⇒⇒⇒⇒⇒ CONTINUOUSCONTINUOUS REACTIONREACTION

ClCl--

2828

CRITICALCRITICAL CHLORIDECHLORIDE CONTENDSCONTENDS OF OF CONCRETECONCRETE

Low Corrosion

Risk

(Electrolythic

Process Stops)

Low Corrosion

Risk (No Oxygen)High Corrosion

Risk

Carbonated

Concrete

Non-carbonated

ConcreteGood Quality

Concrete

50

0.4

Relative Humidity (%)

Cri

tica

lV

alu

esof

Ch

lori

de

Co

nte

nt

of

Co

ncr

ete

(%

of

Cem

ent

Wei

gth

)

85 100

Bad Quality

Concrete

2929

CHLORIDECHLORIDE CONTENTSCONTENTSOF OF CONCRETECONCRETE

Prestressed Concrete 0.08 0.06

ACI 222RBY WEIGHT of CEMENT

Acid Soluble

Chloride (%)

Water Soluble

Chloride (%)

Reinforced Concrete (Humid environment) 0.10 0.08

Reinforced Concrete (Dry environment) 0.20 0.15

Concrete 1.0 1.0

TS EN206-1Max. Cl content by weight of cement

Chloride Content

(%)

Reinforced Concrete 0.20 0.40

Prestressed Concrete 0.10 0.20

30

RELATIONSHIP BETWEEN CONCRETE COVER& CHLORIDE INGRESS

100 200 300 400 500 600 700 800 9000

100

75

50

25

W/C=0.6

W/C=0.5

W/C=0.4

Number of Wetting&Drying Cycle in Saline

Media

Co

ncr

ete

Co

ver

(mm

)

NECESSARY COVER

THICKNESS FORCHLORIDE CONTENT

<%0.2 AFTER 800 CYCLES

W/C =0.4; ⇒⇒⇒⇒ c ≥≥≥≥ 40 mm

W/C =0.5; ⇒⇒⇒⇒ c ≥≥≥≥ 70 mm

W/C =0.6; ⇒⇒⇒⇒ c ≥≥≥≥ 90 mm

ACI 222RW/C =0.4; ⇒⇒⇒⇒ c ≥≥≥≥ 50 mm

W/C =0.45; ⇒⇒⇒⇒ c ≥≥≥≥ 65 mm

3131

CONTACTCONTACT CORROSIONCORROSION

TWOTWO DIFFERENTDIFFERENT

METALSMETALS ((ININ CONTACTCONTACT))+ + HH22OO + + OO22

GALVANICGALVANIC

BATTERYBATTERY

ANODICANODIC

METALMETALELECTRONELECTRON LOSSLOSS

((MASSMASS LOSSLOSS)) CORROSIONCORROSION

METALSMETALS AT AT UPPERUPPER LEVELSLEVELS OF OF ELECTROMOTIVEELECTROMOTIVE

SERIESSERIES AREARE MOREMORE STABLESTABLE (DO NOT (DO NOT OXIDEOXIDE))

COMPAREDCOMPARED TOTO THETHE METALSMETALS AT AT LOWERLOWER LEVELSLEVELS

CATHODICCATHODIC METAL IS METAL IS STABLESTABLE

RARERARE ININ CONVENTIONALCONVENTIONAL R.F.C. R.F.C. STRUCTURESSTRUCTURES

((EPOXYEPOXY BONDEDBONDED R.F. + R.F. + STEELSTEEL, AL. + , AL. + StSt, , etcetc.).)

32

REINFORCEMENT CORROSION in

CRACKED CROSS-SECTIONS

O2O2

Anodic Reaction at cracked region

(OH)-

Fe+2

(OH)-

Fe+2

Uncracked Large area cathode

MACRO ELEMENT

LARGE AREA : CATHODE

SMALL AREA : ANODE

Fe+2

(OH)-

O2

W

c

MICRO ELEMENT

ANODIC & CATHODIC

AREAS ARE VERY CLOSE TO

EACH OTHER IN CRACK

MAXIMUM ALLOWABLE

CRACK WIDTH

W < 0.2 - 0.3 mm

3333

PERMEABILITYPERMEABILITY –– CORROSIONCORROSIONRELATIONSRELATIONS

MATERIALS

Mix Proportions, Cement type

& Aggregate properties,

Admixtures, etc.

PRODUCTION METHODS

Mixing, Transportation,

Casting, Vibration, Finishing

PROCESSES AFTER

CASTING

Curing, Concrete strength at

loading, service conditions

CO2

Penetration

WATER PENETRATION

(Splashing, Hydraulic pressure,

Immersion, Capillary suction,

O2 PENETRATION

WASHING OUT OF Ca(OH)2PE

RM

EA

BIL

ITY

CARBONATION

DECREASE OF pH value

Cl- PENETRATION

CRACKS, POP-OUTS &

SPALLING OF CONCRETE

CO

RR

OS

ION

3434

PRODUCTSPRODUCTS of of CORROSIONCORROSION

LATERAL CRACKS BETWEEN

COVER & REINFORCEMENT

CracksSteel

Pop-outsSteel

0 1 2 3 4 5 6 7

Fe

FeO

Fe3O4

Fe2O3

Fe(OH)4

Fe(OH)3

Fe(OH)3 . 3H2O

Volume (cm3)

CRACKS DUE TO CRACKS DUE TO

SWELLINGSWELLING

RUST PRODUCTSRUST PRODUCTS

VOLUME INCREASE UP VOLUME INCREASE UP

TO TO ∼∼∼∼∼∼∼∼6 TIMES 6 TIMES

3535

CORROSION HAZARDS CORROSION HAZARDS

BEGINNING OF ATMOSPHERIC TYPES OF CORROSION DUE

TO AIR EXPOSURE

CRACK OF CONCRETE COVER

CHANGE IN DEFORMATION PROPERTIES &

TENSILE STRESS

LOSS OF X-SECTION

RUSTING OF REINFORCEMENT

LOSS OF BOND BETWEEN CONCRETE &

REINFORCEMENT

3636

REINFORCEMENT CORROSIONREINFORCEMENT CORROSION

The effect of reinforcement cross-sectional area loss of on moment carrying capacity

0

10

20

30

40

50

5 15 25 35 45

Donatıda Kesit Kaybı %

Mo

me

nt

Taşım

a K

ap

asit

esin

de

Kayı

p %

2∅∅∅∅14

2∅∅∅∅14

4∅∅∅∅16 4∅∅∅∅16

30x70 cm

N=100 ton

Transition from ductile to brittle behaviour Transition from ductile to brittle behaviour

without warning sign ! without warning sign !

RF area loss (%)

Moment carrying

capacity loss (%)

3737

HAZARDS of CORROSION HAZARDS of CORROSION

3838


HAZARDS of CORROSIONHAZARDS of CORROSION

4242


HAZARDS of CORROSIONHAZARDS of CORROSION

4646


4747


4848


4949


5050


5151


5252


5353


5454


5555DATDATÇÇA PORTA PORT


5656


5757DATDATÇÇA PORTA PORT


5858


5959


6060


6161


6262

CORROSION DETERIORATION OF COLUMNS CORROSION DETERIORATION OF COLUMNS

UNDER THE ATATURKUNDER THE ATATURK’’S MAUSOLEUMS MAUSOLEUM


6363


6464


6565


6666


6868

Corrosion rate of reinforcementElectrochemical measurements

160 mm

75 mm

20 mm

60 mmφ12, φ16, φ20

Gamry PCI4/300 Potentiometer

6969

Reinforced concrete Plain reinforcement

7070

CLASSIFICATION OF ENVIRONMENTAL CLASSIFICATION OF ENVIRONMENTAL EXPOSURE EXPOSURE ––TS EN206 TS EN206

CORROSION RISK DUE TO CARBONATION

NO RISK OF CORROSION OR

DETERIORATION

XC1 XC2 XC3 XC4X0Max.

W/C0.65 0.60 0.55 0.50-----

Min.

STRENGTHC20 C25 C30 C30C14

Min. CEMENT

DOSAGE (kg/m3)260 280 280 300------

X0 : VERY DRY (Very low humidity, interior of buildings)

XC1 : DRY (Low humidity, interior of buildings)

XC2 : HUMID ENVIRONMENT (Components exposed to water, Foundations)

XC3 : MODERATE HUMIDITY (not exposed to rain, int./ext. components)

XC4 : CONTINOUSLY DRY-WET ENVIRONMENT (one face exposed to water)

7171

CLASSIFICATION OF ENVIRONMENTAL CLASSIFICATION OF ENVIRONMENTAL EXPOSURE EXPOSURE ––TS EN206 TS EN206

XD1 : HUMID, RARELY DRY (Splashing of water containing Chloride ions)

XD2 : MODERATE HUMIDITY (Swimming pools, industrial water)

XD3 : CONTINUOUSLY DRY-WET ENVIRONMENT (Bridges, Floors, car parking structures)

0.55Max.

W/C0.55 0.45

PRECAUTIONS DUE TO CHLORIDE

CORROSION (EXCEPT SEA WATER)

XD1 XD2 XD3

Min.

STRENGTH C30 C30 C35

Min. CEMENT

DOSAGE (kg/m3)300 300 320

7272

PRECAUTIONS OF STANDARDS FOR CONCRETE DESIGN & COVER TO SUSTAIN DURABILITY

Are GENERALLY BASED ON 2 APPROVALS

1. 50 YEARS SERVICE LIFE

2. MAX. AGGREGATE SIZE IS 20-32 mm

FOR MORE SERVICE LIFE

PRECAUTIONS FOR CORROSIONPRECAUTIONS FOR CORROSION

INCREASE THE COVER

EX: FOR 100 YEARS

ADD 10 mm

CEMENT DOSAGE and etc. HAS TO BE TAKEN INTO CONSIDERATION

Cnom = Cmin +∆∆∆∆cCOVER DETAILED INTHE PROJECT: Cnom

∆∆∆∆c:

THE COVER DEPENDENT ON PROJECT TOLERANCES, QUALITY CONTROL and ETC.

(GENERALLY 5 mm)

7373

Average Relative Humidity of Concrete (%)

Corr

osi

on

Ris

k F

act

or

Rel

ate

d t

o C

on

cret

e C

over

50 60 70 80 90 100

2.5

2.0

1.5

1.0

0.5

0

Existance of

Chloride ions

Normal

environment

DEPTH OF COVER SHOULD BE INCREASED BASED ON RISK FACTOR

Concrete cover Concrete cover –– Corrosion Corrosion Risk Risk

7474

CONCRETE COVER TS500 (2000)CONCRETE COVER TS500 (2000)

COLUMNS & BEAMS INDOORS ≥20 mm

ELEMENT in CONTACT with SOIL ≥50 mm

MINIMUM

THICKNESS

≥25 mmCOLUMNS & BEAMS EXPOSED

to ATMOSPHERIC CONDITIONS

≥15 mmSHEAR WALLS, CURTAINS, PLATES

≥15 mmFOLDED PLATES & MEMBRANES

7575

CONCRETE COVER CONCRETE COVER

CORROSION DUE TO

CARBONATION

NO

RISK

XC1 XC2/XC3 XC4X0 XD1/XD2/XD3 XS1/XS2/XS3

CORROSION DUE TO

CHLORIDES

CORROSION DUE TO

SEA WATER

REINFORCED

CONCRETE

Cmin (mm)15 25 3010 45 45

PRESTRESSED

CONCRETE

Cmin (mm)25 35 4020 55 55

prEN1992-1

7676

CONCRETE COVERCONCRETE COVER(mm)(mm)

I : PROTECTED SURFACES AGAINST AGGRESSIVE ENVIRONMENT

20

35

----

----

----

0.60

35

300

20

30

40

50

----

0.55

40

325

20

25

30

40

60

0.50

45

350

20

20

25

30

50

0.45

50

400

I

II

III

IV

V

MAX W/C

CONCRETE STRENGTH

MIN CEMENT DOSAGE

25

----

----

----

----

0.65

30

275

III : EXPOSED TO EXCESSIVE RAIN, DRYING & WETTING

II : PROTECTED SURFACES EXCESSIVE RAIN & FROST DAMAGE, EXISTANCE OF CONDENSATION

IV : SEA WATER, DE-ICING AGENT, FREEZE-THAWING

V : ACIDIC WATER (pH≤≤≤≤4.5), WEARING, EROSION

7777

STAINLESS STEEL EXPENSIVE & POOR BOND

EPOXY PAINTING GOOD CHEMICAL RESISTANCE, BRITTLENESS, MAY CRACKS DURING STEEL WORKS (BENDING ETC.), HIGH COST, POOR BOND, LONG TERM PERFORMANCE IS NOT KNOWN

GALVANIZING WITH ZINC

LONG TERM PERFORMANCE IS NOT CLEAR, LOSS OF BOND, CRACK DEVELOPMENT DURING STEEL WORKS, WELDING IS NOT POSSIBLE

SPECIAL METHODS & MATERIALSSPECIAL METHODS & MATERIALS

7878

GLASS FIBER REINFORCEMENT

FOREGOING RESEARCH NOT COMPLETED, BRITTLENESS, NOT WORKABLE, MAY CAUSE ASR, ASR RESISTANT TYPE IS VERY EXPENSIVE

CHEMICAL ADMIXTURE (CORROSION INHIBITATORS)

SUCCESSFUL RESULTS WITH CALCIUM NITRATE, LONG TERM PERFORMANCE IS NOT CLEAR, RETARDING EFFECT, MAY CAUSE ASR, LOSS OF COMPRESSIVE STRENGTH, EFFLORESENCE


7979

CATHODIC PROTECTION

USING EXPANDABLE RECHANGEABLE METAL SUCH AS ZINC & MAGNESIUM THEY CORRODE INSTEAD OF STEEL, APPLICATION DIFFICULTY IN REINFORCED CONCRETE

CATHODIC PROTECTION BY AC CURRENT

CORROSION IS PREVENTED BY REVERSING ELECTRO-POTENTIAL OF STEEL, HARDNESS OF APPLICATION UNIFORM DIRECT CURRENT, RISK OF HYDROGEN BRITTLENESS


8080

DURABILITYDURABILITY of of CONCRETECONCRETESTRUCTURESSTRUCTURES

PARTPART 33

Prof. Dr. Prof. Dr. Halit YAZICIHalit YAZICI

DURABILITY of CONCRETE...

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