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Civil engineering, transporation engineering, Bitumen tests
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AIM:
(i)Tomeasuretheductilityofagivensampleofbitumen
(ii)Todeterminethesuitabilityofbitumenforitsuseinroadconstruction.
APPARATUS:
TheapparatusasperIS:12081978consistsof
(i)Briquettemould:Itismadeofbrass.Circularholesareprovidedatendscalledclipstogripthefixedandmovableendsofthetestingmachine.Themouldwhenproperlyassembledformabriquettespecimenoffollowingdimensions.
Totallength75.00.5mm
Distancebetweenclips30.00.3mm
Widthatmountofslip20.00.2mm
Widthatminimumcrosssection
(halfwaybetweenclips)10.00.1mm
Thicknessthroughout10.00.1mm
(ii)Waterbath:Abathmaintainedwithin27.00.1Cofthespecifiedtesttemperaturecontainingnotlessthan10litresofwater,thespecimenbeingsubmergedtoadepthofnotlessthan10cmsandsupportedonaperforatedshellandlessthan5cmsfromthebottomofthebath.
(iii)Testingmachine:Forpullingthebriquetteofbituminousmaterialapart,anyapparatusmaybeusedwhichissoconstructedthatthespecimenwillbecontinuouslysubmergedinwaterwhilethetwoclipsarebeingpulledaparthorizontallyatauniformspeedof502.5mm
DUCTILITY OF BITUMEN
perminute.
(iv)Thermometer.Range044Candreadableupto0.2C
THEORY:
Theductilitytestgivesameasureofadhesivepropertyofbitumenanditsabilitytostretch.Inflexiblepavementdesign,itisnecessarythatbindershouldformathinductilefilmaroundaggregatessothatphysicalinterlockingoftheaggregatesisimproved.Bindermaterialhavinginsufficientductilitygetscrackedwhensubjectedtorepeatedtrafficloadsanditprovidesperviouspavementsurface.Ductilityofabituminousmaterialismeasuredbythedistanceincentimeterstowhichitwillelongatebeforebreakingwhentwoendsofstandardbriquettespecimenofmaterialarepulledapartataspecifiedspeedandspecifiedtemperature.
PROCEDURE:
(i)Meltthebituminoustestmaterialcompletelyatatemperatureof75Cto100Cabovetheapproximatesofteningpointuntilitbecomesthoroughlyfluid.
(ii)StrainthefluidthroughISsieve30.
(iii)Afterstirringthefluid,pouritinthemouldassemblyandplaceitonabrassplate.Inordertopreventthematerialundertestfromsticking,coatthesurfaceoftheplateandinteriorsurfacesofthesidesofthemouldwithmercuryorbyamixtureofequalpartsofglycerineanddextrine.
(iv)Afterabout3040minutes,keeptheplateassemblyalongwiththesampleina
waterbath.Maintainthetemperatureofthewaterbathat27Cforhalfanhour.
(v)Removethesampleandmouldassemblyfromthewaterbathandtrimthespecimenbylevellingthesurfaceusingahotknife.
(vi)Replacethemouldassemblyinwaterbathfor80to90minutes.
(vii)Removethesidesofthemould.
(viii)Hooktheclipscarefullyonthemachinewithoutcausinganyinitialstrain.
(ix)Adjustthepointertoreadzero.
(x)Startthemachineandpullclipshorizontallyataspeedof50mmperminute.
(xi)Notethedistanceatwhichthebitumenthreadofspecimenbreaks.
Meanoftwoobservationsroundedtonearestwholenumberisductilityvalue.
Note:Machinemayhaveaprovisiontofixtwoormoremouldssoastotestthreespecimenssimultaneously.
PRECAUTIONS:
(i)Theplateassemblyuponwhichthemouldisplacedshallbeperfectlyflatandlevelsothatthebottomsurfaceofthemouldtouchesitthroughout.
(ii)Infillingthemould,careshouldbetakennottodistortthebriquetteandtoseethatnoairpocketiswithinthemouldedsample.
OBSERVATIONS:
(i)BitumenGrade=
(ii)PouringTemperature=
(iii)TestTemperature=
(iv)Periodofcoolinginminutes
(a)Inair=
(b)Inwaterbathbeforetrimming=
(c)Inwaterbathaftertrimming=
1
23
(a)InitialReading
(b)FinalReading
RESULT:
Ductilityvalue=
RECOMMENDEDVALUE:
Suitabilityofbitumenisjudgeddependingonitstypeandproposeduse.Bitumenwithlowductilityvaluemaygetcrackedespeciallyincoldweather.MinimumvaluesofductilityspecifiedbyISIforvariousgradesareasfollows.
Sourceofpavingbitumenandpenetrationgrade
Minductilityvalue(cms)
AssamPetroleumA25 5
A35 10
A45 12
A65,A90&A200 15
BitumenfromsourcesotherthanAssamPetroleumS35
50
S45,S65&S90 75
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