Carbonation chloride penetration_of_concrete_structures
12
l i l i l i l i l i l i Annual Concrete Seminar 2005 Annua Concrete Sem nar 2005 1 Carbonation & Chloride Carbonation & Chloride Penetration of Conc rete Penetration of Conc rete S truc tu res S truc tu res Dr Tommy o o Dr Tommy o o City Univers ity of Hong Kong City Univers ity of Hong Kong Annual Concrete Seminar 2005 Annua Concrete Sem nar 2005 2 Du rable conc rete mus t have the abilityto Du rable conc rete mus t have the abilityto w iths tand the potentially deteriorative w iths tand the potentially deteriorative conditionsto which it c an reas onablybe conditionsto which it c an reas onablybe epec ted to be epos ed epec ted to be epos ed Annual Concrete Seminar 2005 Annua Concrete Sem nar 2005 3 Def inition of Conc rete Du rability Def inition of Conc rete Du rability ¢ Res is tanc e to phys ic al and chemic al Res is tanc e to phys ic al and chemic al deterioration of conc rete resu lting f rom deterioration of conc rete resu lting f rom ¢ I nterac tion w ith env ironment I nterac tion w ith env ironment - - e ternal e ternal ¢ I nterac tion between cons tituents I nterac tion between cons tituents - - internal internal ¢ P rotec tion of embedded s teel f rom P rotec tion of embedded s teel f rom corros ion p roc ess es corros ion p roc ess es Annual Concrete Seminar 2005 Annua Concrete Sem nar 2005 4 Du rability Du rability Concrete Deterioration Concrete Deterioration Physical Physical Deterioration Deterioration Chemical Chemical Deterioration Deterioration Reinforcement Reinforcement Corrosion Corrosion Carbonation Carbonation Chlorides Chlorides Annual Concrete Seminar 2005 Annua Concrete Sem nar 2005 5 Mechanism of Carbonation Mechanism of Carbonation Ca(0H) Ca(0H) 2 2 + C0 + C0 2 2 ‚ ‚ CaC0 CaC0 3 3 + H + H 2 2 0 0 involves a phys iochemic al reac tion involves a phys iochemic al reac tion between atmospheric c arbon dio ide and between atmospheric c arbon dio ide and the c alc ium hydro ide generated in the c alc ium hydro ide generated in c ement hydration The p rec ip itation of c ement hydration The p rec ip itation of c alc ium c arbonate as shown in the c alc ium c arbonate as shown in the f ollow ing equation reduc es the pH level of f ollow ing equation reduc es the pH level of conc rete conc rete Annual Concrete Seminar 2005 Annua Concrete Sem nar 2005 6 Mechanism of Carbonation Mechanism of Carbonation ¢ S tep 1 S tep 1 H H 2 2 0+C0 0+C0 2 2 = HC0 = HC0 3 3 - - + H + H + + HC0 HC0 3 3 - - = C0 = C0 3 3 2 2 - - + H + H + + ¢ S tep 2 S tep 2 Ca(0H) Ca(0H) 2 2 + 2H + 2H + + + C0 + C0 3 3 2 2 - - = CaC0 = CaC0 3 3 +2H +2H 2 2 0 0 ¢ This neu tralis ation reac tion penetrates This neu tralis ation reac tion penetrates g radually g radually into into the conc rete su rf ac e the conc rete su rf ac e ¢ Penetration Penetration Rate Rate =k time =k time 1l 2 1l 2 1
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Transcript of Carbonation chloride penetration_of_concrete_structures
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Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 11
Carbonation & Chloride Carbonation & Chloride
Penetration of Concrete Penetration of Concrete
StructuresStructures
Dr Tommy ooDr Tommy oo
City University of Hong KongCity University of Hong Kong
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 22
Durable concrete must have the ability to Durable concrete must have the ability to withstand the potentially deteriorative withstand the potentially deteriorative conditions to which it can reasonably be conditions to which it can reasonably be e pected to be e posed e pected to be e posed
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 33
Definition of Concrete DurabilityDefinition of Concrete Durability
¢¢ Resistance to physical and chemical Resistance to physical and chemical deterioration of concrete resulting fromdeterioration of concrete resulting from ¢¢ Interaction with environment Interaction with environment -- e ternale ternal ¢¢ Interaction between constituents Interaction between constituents -- internalinternal
¢¢ Protection of embedded steel from Protection of embedded steel from corrosion processescorrosion processes
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 44
DurabilityDurability
Concrete DeteriorationConcrete Deterioration
PhysicalPhysical DeteriorationDeterioration
ChemicalChemical DeteriorationDeterioration
ReinforcementReinforcement CorrosionCorrosion
CarbonationCarbonation ChloridesChlorides
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 55
Mechanism of CarbonationMechanism of Carbonation
Ca(0H)Ca(0H)2 2 + C0+ C02 2 ‚‚ CaC0CaC033 + H+ H2200
involves a physiochemical reaction involves a physiochemical reaction between atmospheric carbon dio ide and between atmospheric carbon dio ide and the calcium hydro ide generated in the calcium hydro ide generated in cement hydration The precipitation of cement hydration The precipitation of calcium carbonate as shown in the calcium carbonate as shown in the following equation reduces the pH level of following equation reduces the pH level of concrete concrete
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 66
Mechanism of CarbonationMechanism of Carbonation
¢¢ Step 1Step 1 HH220+C00+C02 2 = HC0= HC033-- + H+ H++
HC0HC033-- = C0= C033
22-- + H+ H++
¢¢ Step 2Step 2 Ca(0H)Ca(0H)22 + 2H+ 2H++ + C0+ C033 22--
= CaC0= CaC033 +2H+2H2200 ¢¢ This neutralisation reaction penetrates This neutralisation reaction penetrates gradually gradually intointo the concrete surface the concrete surface
¢¢ Penetration Penetration Rate Rate = k time= k time1l21l2
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Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 77
‹‹Change in PhChange in Ph
The atmosphericcarbon dio ide diffusesThe atmosphericcarbon dio ide diffuses into the hardened concrete through poresinto the hardened concrete through pores and when carbonation reaction takesplace,and when carbonation reaction takesplace, the alkalinityofthe concrete reducesfromthe alkalinityofthe concrete reducesfrom1 to below91 to below9
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 88
FactorsaffectingcarbonationFactorsaffectingcarbonation
¢¢ HumidityHumidity- ideally5 ideally5 -7 %7 % ¢¢ lower, not enough waterlower, not enough water ¢¢ higher water inhibitsC0higher water inhibitsC022 diffusiondiffusion
¢¢ TemperatureTemperature - worse in hotworse in hot environmentsenvironments
¢¢ Concentration ofC0Concentration ofC022 gasin atmospheregasin atmosphere ¢¢ Normally 3% but increasingannuallyNormally 3% but increasingannually ¢¢ Higher in cities, due to motor vehiclesandHigher in cities, due to motor vehiclesand fossil fuel burningfossil fuel burning
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 99
TestingMethodTestingMethod The measurement ofcarbonation depth using the phenolphthalein solution wascarried out by sprayingthe indicator on the split surface ofthe concrete cylinder The solution became a pink colorin the carbonated concrete and can be differentiated from the uncarbonated concrete, giving a distinct boundary marking the carbonation front Acarbonation depth upto an accuracyof 5mm can be identified with the naked eye
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 1010
Samples sprayed with phenolphthalein solution
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 1111
‹‹MechanismMechanism-- phenolphthalein solution methodphenolphthalein solution method
TheThe colourless acidlbase indicatorcolourless acidlbase indicator (phenolphthalein solution) monitoringthe(phenolphthalein solution) monitoringthe carbonation depth is by capturing thecarbonation depth is by capturing the depth at which the pH isabout 9depth at which the pH isabout 9
It indicatesthe boundaryat which theIt indicates the boundary at which the carbonated front meets with thecarbonated front meets with the uncarbonateduncarbonated concrete, where concrete isconcrete, where concrete is alkalinealkaline
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 1212
‹‹oimitationoimitation
TThere e istsa partiallycarbonated zonehere e istsa partiallycarbonated zone where the pHwhere the pH value isnot easilydetectedvalue isnot easilydetected usingphenolphthaleinusingphenolphthalein indicator Pastindicator Past evidence hasshown that carbon dio ideevidence hasshown that carbon dio ide could react at the depthsgreater thancould react at the depthsgreater than those indicated bythose indicated by phenolphthaleinphenolphthalein indicatorindicator
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Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 1313
FTIRFTIR–– Innovative ApproachInnovative Approach
FTFT-IRspectroscopyisa powerful tool forIRspectroscopyisa powerful tool for determiningthe structure ofthe functionaldeterminingthe structure ofthe functional groupsthat build upthe moleculesWhengroupsthat build upthe molecules When the IRthe IR-light passesthrough the sample,light passesthrough the sample, each functional group resonates in itseach functional group resonates in its characteristic absorption frequencies incharacteristic absorption frequencies in the infrared region ofthe electromagneticthe infrared region ofthe electromagnetic spectrumspectrum
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 1414
quipment quipment FTFT--IRIR
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 1515
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ConcreteConcrete
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 1616
CCarbonationarbonation - transformation of thetransformation of the C=O bonds of COC O bonds of CO22 to the formation ofto the formation of CC–O bonds in the CaCOO bonds in the CaCO33..
TThe three Che three C–O bonds in the inorganicO bonds in the inorganic carbonate of the CaCOcarbonate of the CaCO33 are arranged inare arranged in aa trigonaltrigonal planar pattern.planar pattern.
TThe characteristic peak of the Che characteristic peak of the C–OO functional group in the wave numberfunctional group in the wave number range of 1410range of 1410–1510 cm1510 cm��11 waswas used toused to identify carbonation in a complexidentify carbonation in a complex concrete composite.concrete composite.
C +
02-
Ca2+
CarbonationCarbonation
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 1717
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Peak1 15Peak1 15
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 1818
¢¢ produces a scientproduces a scientifific measurement ofic measurement of carbonation depthcarbonation depth
¢¢ providing a convenient tool for crossproviding a convenient tool for cross-e aminatione amination
¢¢ overcomingthe deficiencyofresultsfromovercomingthe deficiencyofresultsfrom conventional analytical methodsconventional analytical methods
¢¢ cannot give a continuousline representingcannot give a continuousline representing the carbonation frontthe carbonation front
IRspectrumanalysisIRspectrum analysis
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Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 1919
Test programTest program ¢¢ TTo studythe effectsofinitial curingon theo studythe effectsofinitial curingon the depth ofcarbonationdepth ofcarbonation
¢¢ ThreeThree mimi A, Kand C withA, Kand C with wlcwlcratiosof 38,ratiosof 38, 6and 56and 5
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 2020
For each gradeFor each grade:: ¢¢ 8numbersof1 mmcubes8numbersof1 mm cubesandand ¢¢ 8unitsof18unitsof1 <<xx2 mmhigh cylinders2 mm high cylinders ¢¢ stored in water at 27stored in water at 27773333CC ¢¢ aafter 28days, the cylinderswere coated with epo yfter 28 days, the cylinderswere coated with epo y resin to ensure that the carbon dio ide could onlydiffuseresin to ensure that the carbon dio ide could onlydiffuse into the concrete fromtwo endsofthe sampleinto the concrete from two endsofthe sample
¢¢ TThe specimenswere transferred to an enclosed chamberhe specimenswere transferred to an enclosed chamber to accelerate the carbonation processThe concentrationto accelerate the carbonation processThe concentration ofcarbon dio ide in the chamber waskept at 2% andofcarbon dio ide in the chamber waskept at 2% and wasmonitored weeklywith a portable infrared carbonwasmonitored weeklywith a portable infrared carbon dio ide analyzerdio ide analyzer
Test methodTest method
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 2121
Powder sampleswere taken from thePowder samples were taken from the cylinder at depthsof , 1 5, 3 , 5, 6 ,cylinder at depthsof , 1 5, 3 , 5, 6 , 8 , 1 , 12 , 1 , 17 , 2 , and 38 , 1 , 12 , 1 , 17 , 2 , and 3 mm measured from the surface The IRmm measured from the surface The IR spectrum ofeach powder sample wasspectrum ofeach powder sample was mi ed withmi ed with KKrKKr in the proportion of1 : 1in the proportion of1 : 1 to facilitate quantitative measurement ofto facilitate quantitative measurement of carbonation depthcarbonation depth
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 2222
Carbonation depth determined usingFT IR
(air cured concrete, wlc 5)
30daycarbonation age
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 2323
Carbonation depth determined usingFT IR
(air cured concrete, wlc 5)
60daycarbonation age
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 2424
Carbonation depth determined usingFT IR
(air cured concrete, wlc 5)
90daycarbonation age
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Annua Concrete Sem nar 2005Annual Concrete Seminar 2005 3030
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 2525
Carbonation depth determined usingFT IR
(water cured concrete, wlc 5)
30daycarbonation age
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 2626
Carbonation depth determined usingFT IR
(water cured concrete, wlc 5)
60daycarbonation age
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 2727
Carbonation depth determined usingFT IR
(water cured concrete, wlc 5)
90daycarbonation age
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 2828
CComparisonomparison PhenolphthaleinlFTIRPhenolphthaleinlFTIR((waterwater))
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 2929
CComparisonomparison PhenolphthaleinlFTIRPhenolphthaleinlFTIR((airair))
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Carbonation depth increased with timeCarbonation depth increased with time [[phenolphthalein solutionphenolphthalein solution]]
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Annua Concrete Sem nar 2005Annual Concrete Seminar 2005 3131
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Carbonation depth increased with timeCarbonation depth increased with time [[FTFT--IRSpectrumIRSpectrum]]
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 3232
Comparison ofcarbonation rate constant KComparison ofcarbonation rate constant K
[1] Roy SK Poh KB Northwood DO Durability of concrete accelerated carbonation and weathering studies Building and Environment 1999;34:597 606
[2] Roy SK Northwood DO Poh KB E!ect of plastering on the carbonation of a 19 year old reinforced concrete building Construction and Building Materials 1996;10(4):267 72
[3] Balayssac JP Detriche ChH Grandet J E!ect of curing upon carbonation of concrete Construction and Building Materials 1995;9(2):91 5
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 3333
Differences(9 daysDifferences(9 daysCarbonation depthCarbonation depth))
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 3434
Schematicmodel ofcarbonation front usingSchematicmodel ofcarbonation front using phenolphthalein indicator and IRspectrumanalysisphenolphthalein indicator and IRspectrum analysis
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 3535
Carbonation depth by way of an IR spectroscopic test can be determined by observing the occurrence of C 0 characteristic peaks relative to the background noise at wave number 1 15 IR spectrometry gives more consistent results with lower variationsin measurement than a phenolphthalein solution The carbonation rate constant found byIRspectrum analysis was23 9% higher than that obtained using the phenolphthalein indicator
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 3636
¢ 0ur findingssuggested that FT IR spectrum analysis provides a useful tool for providing early warnings of carbonation in structural surveys
¢ Compared with carbonation test using Phenolphthalein indicator, using FT IR analysis is more accurate
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Concrete & Steel Corrosion
Carbonation
Others than sea water e. g. de-icing salts
ChloridesChlorides
Sea water
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 3838
Factorsaffectingchloride attackFactorsaffectingchloride attack
¢¢ Concentration ofchloridesConcentration ofchlorides- corrosion willcorrosion will not occur belowa threshold levelnot occur belowa threshold level (somewhere between 1 and %)(somewhere between 1 and %)
¢¢ Humidity, alternate wettingand dryingHumidity, alternate wettingand drying ¢¢ TemperatureTemperature - worse in hot climatesworse in hot climates ¢¢ Concrete permeabilityand chlorideConcrete permeabilityand chloride bindingcapacity, cement content andbindingcapacity, cement content and typetype
¢¢ PFAandPFAand SFSFwill helpresist chloridewill helpresist chloride ingressingress
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 3939
TestsofChloride ionsdiffusionTestsofChloride ionsdiffusion
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 4040
Type ofCementType ofCement PastePaste
Coe
ffC
oeff
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ide
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22 ss-11
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Strength (Strength (MMPPaa))
OPC
PFA 30%
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Mechanism ofchlorideMechanism ofchloride--inducedcorrosioninducedcorrosion
¢¢ Anode ReactionAnode Reaction
FeFe – 22ee ‚‚ FeFe2+2+
¢¢ Cathode ReactionCathode Reaction
2H2H220 + 00 + 022 ++ ee ‚‚ 0H0H-
H2O H2OO2 O2
Cl- Cl-
OH- OH-Cathode Cathode
Anode
e - e -Fe2+
rust rust Cl-
Cl-
Cl-Cl- Cl-
Cl-Cl-
FeFe2+2+ + 2Cl+ 2Cl- ‚‚ FeClFeCl22
FeClFeCl22 + 2H+ 2H2200 ‚‚ Fe(0H)Fe(0H)22 + 2HCl+ 2HCl
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 4242
SourcesofChloridesSourcesofChlorides
¢¢ Contact with sea waterContact with sea water ¢¢ FromdeFrom de-icingsaltsicingsalts ¢¢ Frombeach or sea dredged aggregatesFrom beach or sea dredged aggregates ¢¢ Fromaccelerators(chlorideFrom accelerators(chloride-basedbased admi turesnowprohibited)admi turesnowprohibited)
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Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 4343
Factorsaffectingchloride attackFactorsaffectingchloride attack
¢¢ Concentration ofchloridesConcentration ofchlorides- corrosion willcorrosion will not occur belowa threshold levelnot occur belowa threshold level (somewhere between 1 and %)(somewhere between 1 and %)
¢¢ Humidity, alternate wettingand dryingHumidity, alternate wettingand drying ¢¢ TemperatureTemperature - worse in hot climatesworse in hot climates ¢¢ Concrete permeabilityand chlorideConcrete permeabilityand chloride bindingcapacity, cement content andbindingcapacity, cement content and typetype ¢¢ PFAandPFAand SFSFwill helpresist chloride ingresswill helpresist chloride ingress
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 4444
Relation between permeabilityandwater/cementratioforcementpastes
Ref: Neville A M, PropertiesofConcrete (3rd ed ), 1981
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 4545
Relation between permeabilityandcapillaryporosityofcementpaste
Ref: Neville A M, PropertiesofConcrete (3rd ed ), 1981
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 4646
Test programTest program
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 4747
¢¢ The specimensafter 28dayswere cut into twoThe specimensafter 28dayswere cut into two partsparts
¢¢ The vertical surface ofconcrete cylinder wasThe vertical surface ofconcrete cylinder was sealed by epo y to avoid the diffusion ofsealed by epo y to avoid the diffusion of chloride ion through thissurfacechloride ion through thissurface
¢¢ Test cylinderswere soaked in the salt solutionTest cylinderswere soaked in the salt solution for one month and two monthsfor one month and two months
¢¢ At each month, specimenswere taken out fromAt each month, specimenswere taken out from the salt solution and dried for 2 hoursat roomthe salt solution and dried for 2 hoursat room temperature and humidity The surface ofthetemperature and humidity The surface ofthe specimenswere cleaned bycloth to remove thespecimenswere cleaned bycloth to remove the salt crystalsalt crystal
¢¢ PotentiometricPotentiometricTitration Test andTitration Test and AgN0AgN033 SolutionSolution SprayTest were taken to determine the chlorideSprayTest were taken to determine the chloride content at different depth and the ma imumcontent at different depth and the ma imum depth ofpenetrationdepth ofpenetration
6 dayspondingtest
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 4848
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Surface Chloride levelSurface Chloride level (Ky(KyPotentiometricPotentiometricTitration test)Titration test)
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 5050
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 5151
KyAgN03 Solution SprayTest
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 5252
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 5353
Depth ofChloride Penetration ofM1, M2 and M3 under Air Curingafter 2 Months
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 5454
Depth ofChloride Penetration ofM , M5and M6under Air Curingafter 2 Months
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Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 5555
Depth ofChloride Penetration ofM2 under Air Curing and Water Curingafter 2 Months
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 5656
Comparison ofDepth ofChloride Penetration Ketween M1 and M under Air Curingafter 1 Months
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 5757
Depth ofChloride Penetration ofM3 under Air Curing after 1 and 2 MonthsImmersion
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 5858
Chloride ingressprofiles (byPotentiometricTitration Test)
The 2 month chloride ingressprofiles are shown byfollowingfigures The limit ofchloride content ofconcrete is 1% bymassofcement Ahorizontal red line isdrawn in each figure to indicate the depth ofpenetration at 1% limit
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Chloride ingressprofiles (byPotentiometricTitration Test)
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 6060
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Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 6363 Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 6464
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 6565 Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 6666
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Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 6969
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FTIRFTIR–– Chloride penetration �Chloride penetration �
Annual Concrete Seminar 2005Annua Concrete Sem nar 2005 7070
Thank�ou�Thank�ou�
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