Building Materials, Third Edition

MaterialsforMakingConcrete-IIAggregates 193

Flakiness Index and Elongation IndexTest(IS: 2386 (Part I))

Becauseoflargenumberofflakyparticlesinthecoarseaggregatemorevoidsareformedin
theconcreteconsequentlymoremortarisrequiredto fillthevoids,resultinginuneconomy.
Also, durabilityofconcretewillbeaffected.
Forflakinessindex(F.I)andelongationindex(E.I)sufficientquantityofaggregateis taken
so as toprovideatleast 200 piecesofanyfractionto betested.Thesampleis sievedthrough
I.S.sievesasgiveninTable6.3.

Table6.3 Dimensions of Thickness andlengthGuages

Sizeofaggregate Thicknessgauge(mm) Lengthgauge(mm)

Passingthrough Retainedon

ISsieve ISsieve

63 mm 50 mm 33.90

50 mm 40 mm 27.00 81.0

40 mm 25 mm 19.50 58.5

31.5mm 25 mm 16.95

25 mm 20 mm 13.50 40.5

20 mm^16 mm 10.80 32.4

16 mm 12.5mm 8.55 25.6

12.5mm 10 mm 6.75 20.2

10 mm 6.3mm 4.89 14.7

(J) 50 40 (L)

THESE SIZES MARKED ON GAUGE

FordeterminingF.Ltheaggregateretainedon sievesareseparated.Now,eachaggregate
pieceispassedthroughthecorrespondingslotinthethicknessgauge(Fig. 6.4).Flakinessindex
isgivenby,

(B) '.6mm Thick MS SHEET ROLLED OVER B mm~BAR

All dimensionsin millimetres

Fig.6.4Thickness Gauge

F.I=Weightofaggregatepassingthroughtheslotofthet~icknessgaugex 100

Totalwieghtofsample

FordeterminingF.I,theaggregatearesievedthroughthecorrespondingsieves.Aggregate
retainedon eachsieveareseparated.Theneachaggregatepieceispassedthroughthe
correspondingslotoflengthgauge(Fig. 6.5)

E.I=Weightoftheaggregateretainedonlengthgaugex 100

Totalwieghtofaggregate