durability of concrete...
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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 CORROSION HAZARDS of CORROSION
HAZARDS of CORROSIONHAZARDS of CORROSION
HAZARDS of CORROSIONHAZARDS of CORROSION
HAZARDS of CORROSIONHAZARDS of CORROSION
4242
HAZARDS of CORROSION HAZARDS of CORROSION
HAZARDS of CORROSIONHAZARDS of CORROSION
HAZARDS of CORROSIONHAZARDS of CORROSION
HAZARDS of CORROSIONHAZARDS of CORROSION
4646
HAZARDS of CORROSION HAZARDS of CORROSION
4747
HAZARDS of CORROSION HAZARDS of CORROSION
4848
HAZARDS of CORROSION HAZARDS of CORROSION
4949
HAZARDS of CORROSION HAZARDS of CORROSION
5050
HAZARDS of CORROSION HAZARDS of CORROSION
5151
HAZARDS of CORROSION HAZARDS of CORROSION
5252
HAZARDS of CORROSION HAZARDS of CORROSION
5353
HAZARDS of CORROSION HAZARDS of CORROSION
5454
HAZARDS of CORROSION HAZARDS of CORROSION
5555DATDATÇÇA PORTA PORT
HAZARDS of CORROSION HAZARDS of CORROSION
5656
HAZARDS of CORROSION HAZARDS of CORROSION
5757DATDATÇÇA PORTA PORT
HAZARDS of CORROSION HAZARDS of CORROSION
5858
HAZARDS of CORROSION HAZARDS of CORROSION
5959
HAZARDS of CORROSION HAZARDS of CORROSION
6060
HAZARDS of CORROSION HAZARDS of CORROSION
6161
HAZARDS of CORROSION HAZARDS of CORROSION
6262
CORROSION DETERIORATION OF COLUMNS CORROSION DETERIORATION OF COLUMNS
UNDER THE ATATURKUNDER THE ATATURK’’S MAUSOLEUMS MAUSOLEUM
HAZARDS of CORROSION HAZARDS of CORROSION
6363
HAZARDS of CORROSION HAZARDS of CORROSION
6464
HAZARDS of CORROSION HAZARDS of CORROSION
6565
HAZARDS of CORROSION HAZARDS of CORROSION
6666
HAZARDS of CORROSION HAZARDS of CORROSION
6767
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
SPECIAL METHODS & MATERIALSSPECIAL METHODS & MATERIALS
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
SPECIAL METHODS & MATERIALSSPECIAL METHODS & MATERIALS
8080
DURABILITYDURABILITY of of CONCRETECONCRETESTRUCTURESSTRUCTURES
PARTPART 33
Prof. Dr. Prof. Dr. Halit YAZICIHalit YAZICI