Building Materials, Third Edition

(Jacob Rumans) #1
MaterialsforMakingConcrete-ItAggregates 197

Weighedaveragepercentageofsoftparticlescalculatedfrom percentageof testsample
classifiedas softbyweightandby numberofparticlesshouldbereported.

Estimation of organic impuritiesin sand
Sandistested,fororganicimpurities,asdeliveredandwithoutdrying.A350-mlgraduated
glassbottleisfilledtothe75-mlmarkwith 3 percentsolutionofsodiumhydroxideinwater.
Thesandisaddedgraduallyuntilthevolumemeasuredby thesandlayeris 125 ml. The
volumeismadeupto 200 ml byaddingmoresolution.Thebottleisstopperedandshaken
vigorouslyandthenallowed tostandfor 24hours.
Ifthecolouroftheliquidabovethesandisdarkerthanthestandardsolution,prepareda
fresh, thefollowingtestshouldbemade.
2.5ml of 2percentsolutionoftannicacidin 10 percentalcoholisaddedto<)7.5ml of a 3 per
centsodiumhydroxidesolution.It isplacedin a 350 mlbottleandisshakenvigorouslyand
allowedtostandfor 24hours.Thecolourofthisiscomparedwiththesolutionabovethesand.

SpecificGravityand WaterAbsorptionTest(IS: 2386 (Part III))

AggregateLargerthan 10 mm:1\sampleof 2000gofaggregateisusedforconductingthe
test.Aggregatewhichhavebeenartificiallyheatedshouldnotnormallybeused.
Thesampleisthoroughlywashedtoremovefinerparticlesanddust,drainedandthen
placedinthewirebasketandimmersedindistilledwateratatemperaturebetween22-32°e
withacoverofat least 50 mmofwaterabovethe topofthebasket.
Immediatelyafterimmersiontheinterruptedairisremovedfromthesamplebyliftingthe
basketcontainingit 25 mrnabovethebaseofthetankandallowingit todrop 25 timesatthe
rateofaboutonedroppersecond.Thebasketandaggrl'gatearekeptcompletelyimmersed
duringtheoperationandfor,1periodof 24 ±1/2hoursafterwards.Thebasketandthesample
arejoltedandweighedinwater(weightAI)'Thesearethenremovedfromthewaterand
allowedtodrainfora few minutes,afterwhichtheaggregatearegentlyemptiedfromthe
basketon tooneofthedryclothes.andtheemptybasketisreturnedtothewater,jolted 25
timesandweighedinwater(weight1\2)'
Theaggregateplacedon thedryclotharegentlysurfacedriedwiththecloth,andare
completelysurfacedried.Theaggregateart'thenweighed (weightB).
Theaggregatearethercaftcrplacedin anovenatatemperatureof 100-11oDeandmaintained

atthistemperaturefor 24 ±1/2hours.It isthenremovedfromtheoven,cooledintheair-tight

containerandweighed(weightC).Thecomputationsareas under

Specificgravity

Apparentspecificgra\'ity

Waterabsorption(percentofdry\'\'eight) =

C
f)-II
C
C-II
(13~A)Xw'o
C
where A
B
C

theweightingof thesaturatedaggregateinwater(AI~A 2 )
theweightingof thesaturatedsurfacedryaggregateinair
theweightingofoven-driedaggregateinair

Aggregate Between 40 mmand 10 mm: Asampleof about 1000 g of theaggregateis
screenedona 10mmsieve,thoroughlywashedtoremovefineparticlesofdust,andimmersed

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