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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