Building Materials, Third Edition

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