廉慧珍NT492CL扩散系数测定方法.docx
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廉慧珍NT492CL扩散系数测定方法.docx
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廉慧珍NT492CL扩散系数测定方法
UDC691.32/691.53/691.54CONCRETE,MORTARANDCEMENT-BASEDREPAIR
MATERIALS:
CHLORIDEMIGRATIONCOEFFICIENTFROM
NON-STEADY-STATEMIGRATIONEXPERIMENTS
Keywords:
Chlorides,concrete,diffusion,mortar,repairmaterials,migration,testmethod
1SCOPE
Thisprocedureisfordeterminationofthechloridemigrationcoefficientinconcrete,mortarorcement-basedrepairmaterialsfromnon-steady-statemigrationexperiments.
2FIELDOFAPPLICATION
Themethodisapplicabletohardenedspecimenscastinthelaboratoryordrilledfromfieldstructures.Thechloridemigrationcoefficientdeterminedbythemethodisameasureoftheresistanceofthetestedmaterialtochloridepenetration.Thisnon-steady-statemigrationcoefficientcannotbedirectlycomparedwithchloridediffusioncoefficientsobtainedfromtheothertestmethods,suchasthenon-steady-stateimmersiontestorthesteady-statemigrationtest.
3REFERENCES
/1/NTBUILD201,”Concrete:
Makingandcuringofmouldedtestspecimensforstrengthtests”,2nded.,proved1984-05.
/2/NTBUILD202,”Concrete,hardened:
Samplingandtreatmentofcoresforstrengthtests”,2nded.,Approved1984-05.
/3/NTBUILD208,”Concrete,hardened:
Chloridecontent”,2nded.,Approved1984-05.
/4/Tang,LandSørensen,H.E.,”EvaluationoftheRapidTestMethodsforChlorideDiffusionCoefficientofConcrete,NORDTESTProjectNo.1388-98”,SPReport1998:
42,SPSwedishNationalTestingandResearchInstitute,Borås,Sweden,1998.
4DEFINITIONS
Migration:
Themovementofionsundertheactionofanexternalelectricalfield.
Diffusion:
Themovementofmoleculesorionsunderaconcentrationgradientor,morestrictly,chemicalpotential,fromahighconcentrationzonetoalowconcentrationzone.
5SAMPLING
Themethodrequirescylindricalspecimenswithadiameterof100mmandathicknessof50mm,slicedfromcastcylindersordrilledcoreswithaminimumlengthof100mm.ThecylindersandcoresshouldmeettherequirementsdescribedinNTBUILD201andNTBUILD202respectively.Threespecimensshouldbeusedinthetest.
6TESTMETHOD
6.1Principle
Anexternalelectricalpotentialisappliedaxiallyacrossthespecimenandforcesthechlorideionsoutsidetomigrateintothespecimen.Afteracertaintestduration,thespecimenisaxiallysplitandasilvernitratesolutionissprayedontooneofthefreshlysplitsections.Thechloridepenetrationdepthcanthenbemeasuredfromthevisiblewhitesilverchlorideprecipitation,afterwhichthechloridemigrationcoefficientcanbecalculatedfromthispenetrationdepth.
6.2Reagentsandapparatus
6.2.1Reagents
•Distilledorde-ionisedwater.
•Calciumhydroxide:
Ca(OH)2,technicalquality.
•Sodiumchloride:
NaCl,chemicalquality.
•Sodiumhydroxide:
NaOH,chemicalquality.
•Silvernitrate:
AgNO3,chemicalquality.
•Chemicalsforchlorideanalysisasrequiredbythetestmethodemployed(optional,see6.4.6).
6.2.2Apparatus
•Water-cooleddiamondsaw.
•Vacuumcontainer:
capableofcontainingatleastthreespecimens.
•Vacuumpump:
capableofmaintainingapressureoflessthan50mbar(5kPa)inthecontainer.
•Migrationset-up:
Onedesign(seeAppendix1)includesthefollowingparts:
–Siliconerubbersleeve:
inner/outerdiameter100/115mm,about150mmlong.
–Clamp:
diameterrange105∼115,20mmwide,stainlesssteel(seeFigure2inAppendix1).
–Catholytereservoir:
plasticbox,370×270×280mm(length×width×height).
–Plasticsupport:
(seeFigure3inAppendix1).
–Cathode:
stainlesssteelplate(seeFigure3inAppendix1),about0.5mmthick.
–Anode:
stainlesssteelmeshorplatewithholes(seeFigure4inAppendix1),about0.5mmthick.Otherdesignsareacceptable,providedthattemperaturesofthespecimenandsolutionsduringthetestcanbemaintainedintherangeof20to25︒C(see6.4.2).
•Powersupply:
capableofsupplying0∼60VDCregulatedvoltagewithanaccuracyof±0.1V.
•Ammeter:
capableofdisplayingcurrentto±1mA.
•Thermometerorthermocouplewithreadoutdevicecapableofreadingto±1︒C.
•Anysuitabledeviceforsplittingthespecimen.
•Spraybottle.
•Slidecalliperwithaprecisionof±0.1mm.
•Rulerwithaminimumscaleof1mm.
•Equipmentforchlorideanalysisasrequiredbythetestmethodemployed(optional,see6.4.6).
6.3Preparationofthetestspecimen
6.3.1Testspecimen
Ifadrilledcoreisused,theoutermostapproximately10∼20mmthicklayershouldbecutoff(Note1)andthenext50±2mmthicksliceshouldbecutasthetestspecimen.Theendsurfacethatwasnearertotheoutermostlayeristheonetobeexposedtothechloridesolution(catholyte).
Ifa.100×100mmcastcylinderisused,cuta50±2mmthickslicefromthecentralportionofthecylinderasthetestspecimen.Theendsurfacethatwasnearertotheas-castsurfaceistheonetobeexposedtothechloridesolution(catholyte).
Ifa.100×200mmcastcylinderisused,preparethetestspecimenbyfirstcuttingthecylinderintotwohalves(i.e.intotwo.100×100mmcylinders),andthencuttinga50±2mmthickslicefromonehalf.Theendsurfacethatwasnearertothefirstcut(themiddlesurface)istheonetobeexposedtothechloridesolution(catholyte).
Measurethethicknesswithaslidecalliperandreadto0.1mm.
Note1:
Theterm‘cut’heremeanstosawperpendicularlytotheaxisofacoreorcylinder,usingawater-cooleddiamondsaw.
6.3.2Preconditioning
Aftersawing,brushandwashawayanyburrsfromthesurfacesofthespecimen,andwipeoffexcesswaterfromthesurfacesofthespecimen.Whenthespecimensaresurface-dry,placetheminthevacuumcontainerforvacuumtreatment.Bothendsurfacesmustbeexposed.Reducetheabsolutepressureinthevacuumcontainertoapressureintherangeof10–50mbar(1–5kPa)withinafewminutes.Maintainthevacuumforthreehoursandthen,withthevacuumpumpstillrunning,fillthecontainerwiththesaturatedCa(OH)2solution(bydissolvinganexcessofcalciumhydroxideindistilledorde-ionisedwater)soastoimmerseallthespecimens.Maintainthevacuumforafurtherhourbeforeallowingairtore-enterthecontainer.Keepthespecimensinthesolutionfor18±2hours.
6.4Procedure
6.4.1CatholyteandanolyteThecatholytesolutionis10%NaClbymassintapwater(100gNaClin900gwater,about2N)andtheanolytesolutionis0.3NNaOHindistilledorde-ionisedwater(approximately12gNaOHin1litrewater).Storethesolutionsatatemperatureof20–25°C.
6.4.2Temperature
Maintainthetemperaturesofthespecimenandsolutionsintherangeof20–25°Cduringthetest.
6.4.3Preparationofthetest
•Fillthecatholytereservoirwithabout12litresof10%NaClsolution.
•FittherubbersleeveonthespecimenasshowninFigure4inAppendix1andsecureitwithtwoclamps.Ifthecurvedsurfaceofthespecimenisnotsmooth,ortherearedefectsonthecurvedsurfacewhichcouldresultinsignificantleakage,applyalineofsiliconesealanttoimprovethetightness.
•Placethespecimenontheplasticsupportinthecatholytereservoir(seeFigure1inAppendix1).
•Fillthesleeveabovethespecimenwith300mlanolytesolution(0.3MNaOH).
•Immersetheanodeintheanolytesolution.
•Connectthecathodetothenegativepoleandtheanodetothepositivepoleofthepowersupply.
6.4.4Migrationtest
•Turnonthepower,withthevoltagepresetat30V,andrecordtheinitialcurrentthrougheachspecimen.
•Adjustthevoltageifnecessary(asshowninTable1inAppendix2).Afteradjustment,notethevalueoftheinitialcurrentagain.
•Recordtheinitialtemperatureineachanolytesolution,asshownbythethermometerorthermocouple.
•Chooseanappropriatetestdurationaccordingtotheinitialcurrent(seeTable1inAppendix2).
•Recordthefinalcurrentandtemperaturebeforeterminatingthetest.
6.4.5Measurementofchloridepenetrationdepth
•Disassemblethespecimenbyfollowingthereverseoftheprocedurein6.4.3.Awoodenrodisoftenhelpfulinremovingherubbersleevefromthespecimen.
•Rinsethespecimenwithtapwater.
•Wipeoffexcesswaterfromthesurfacesofthespecimen.
•Splitthespecimenaxiallyintotwopieces.Choosethepiecehavingthesplitsectionmorenearlyperpendiculartotheendsurfacesforthepenetrationdepthmeasurement,andkeeptheotherpieceforchloridecontentanalysis(optional).
•Spray0.1Msilvernitratesolutionontothefreshlysplitsection.
•Whenthewhitesilverchlorideprecipitationonthesplitsurfaceisclearlyvisible(afterabout15minutes),measurethepenetrationdepth,withthehelpoftheslidecalliperandasuitableruler,fromthecentretobothedgesatintervalsof10mm(seeFigure5inAppendix1)toobtainsevendepths(notes2,3and4).Measurethedepthtoanaccuracyof0.1mm.
Note2:
Ifthepenetrationfronttobemeasuredisobviouslyblockedbytheaggregate,movethemeasurementtothenearestfrontwherethereisnosignificantblockingbyaggregateor,alternatively,ignorethisdepthiftherearemorethanfivevaliddepths.
Note3:
Ifthereisasignificantdefectinthespecimenwhichresultsinapenetrationfrontmuchlargerthantheaverage,ignorethisfrontasindicativeofthepenetrationdepth,butnoteandreportthecondition.
Note4:
Toobviatetheedgeeffectduetoanon-homogeneousdegreeofsaturationorpossibleleakage,donotmakeanydepthmeasurementsinthezonewithinabout10mmfromtheedge(seeFigure5inAppendix1).
6.4.6Surfacechloridecontent(optional,Note5)
•Fromtheotheraxiallysplitspecimen,cutanapproximately5mmthickslice(Note6)paralleltotheendsurfacethatwasexposedtothechloridesolution(cathol
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