Experiment no 03 Determination of the flakiness and the elongation index for the given aggregate sample.

This test is used to determine the particle shape of the aggregate and each particle shape

1. Determination of the flakiness and the elongation index for the given aggregate sample.
Experiment no: 03
Engr. Sayed Shajedul Hasan.

2. •Theparticleshapeofaggregatesisdeterminedbythepercentagesofflakyandelongatedparticlescontainedinit.Forbasecourseand
constructionofbituminousandcementconcretetypes,thepresenceofflakyandelongatedparticlesareconsideredundesirableasthesecause
inherentweaknesswithpossibilitiesofbreakingdownunderheavyloads.
•Thus, evaluation of shape of the particles, particularly with reference to flakiness and elongation is necessary.
THE FLAKINESS INDEX OF AGGREGATES
isthepercentagebyweightofparticleswhoseleastdimension(thickness)islessthanthree-fifths(0.6times)oftheirmeandimension.This
testisnotapplicabletosizessmallerthan6.3mm.
THE ELONGATION INDEX OF AGGREGATE
isthepercentagebyweightofparticleswhosegreatestdimension(length)isgreaterthannine-fifths(1.8times)theirmeandimension.This
testisnotapplicableforsizessmallerthan6.3mm.
Engr. Sayed Shajedul Hasan.
THEORY

3. Engr. Sayed Shajedul Hasan.
SHAPESOFPARTICLES
The usual shapes of the particles are;
Rounded(rivergravel)FlakinessandElongationIndex
Flaky(laminatedrock)FlakinessandElongationIndex
ElongatedFlakinessandElongationIndex
Angular(crushedrock)
PREFERRED USE OF EACH SHAPE
•Roundedaggregatesarepreferredinconcreteroads(rigid
pavements)astheworkabilityofconcreteincreasesduetothe
lessfrictionbetweenthesurfaces.
•Angularshapeoftheparticlesisdesirableingranularbasecoarse
(flexiblepavement)duetobetterinterlockingandincreased
stability.
•FlakyandElongatedparticlesareconsideredasasourceof
weakness.

4. Engr. Sayed Shajedul Hasan.
SCOPE&SIGNIFICANCE:
Thistestisusedtodeterminetheparticleshapeoftheaggregateandeachparticleshapebeingpreferred
underspecificconditions.
The significance of flakiness & elongation index is as follows;
•Thedegreeofpackingoftheparticlesofonesizedependsupontheirshape.
•Duetohighsurfaceareatovolumeratio,theflakyandelongatedparticleslowertheworkabilityofconcretemixes.
•Flakyandelongatedparticlesareconsideredundesirableforbasecoarseconstructionastheymaycauseweaknesswithpossibilitiesof
brakingdownunderheavyloads.
•BS-1241specifiesaFlakinessindexnotexceeding30%irrespectiveoftheaggregatesize.
•MaximumpermittedElongatedindexis35,40or45%foraggregatesizes2½’’–2’’,1½’’–¾’’&½’’–3/8’’.
•BothFlakinessandElongationtestsarenotapplicabletosizessmallerthen6.3mmi.e.¼’’sieve.

5. Engr. Sayed Shajedul Hasan.
APPARATUS
Balance Sieves Thickness gauge-for flakiness index Length gauge-for elongation index
Sieves required are 63, 50, 37.5, 28, 20, 14, 10 and 6.3 mm (Based on requirement and Gradation of Aggregate).

6. Engr. Sayed Shajedul Hasan.
PROCEDURE
•Sievethesamplethroughthesieves(asspecifiedinthechart).
•Takeaminimumof200piecesofeachfractiontobetestedandweighthem.
•Toseparatetheflakymaterials,gaugeeachfractionforthicknessonathicknessgauge.
•Weighttheflakymaterialpassingthegaugetoanaccuracyofatleast0.1percentofthetestsample.
•Toseparatetheelongatedmaterials,gaugeeachfractionforlengthonalengthgauge
•Toseparatetheelongatedmaterials,gaugeeachfractionforlengthonalengthgauge
•Weightheelongatedmaterialretainedonthegaugetoanaccuracyofatleast0.1percentofthetest
sample.

7. Engr. Sayed Shajedul Hasan.
PRECAUTIONS
•Whilesieving,caremustbetakenthattheparticlesthatarechockedinthesievemustnobeforceddownintothenextsieve.Such
particlesshouldbepushedbackintothesamesieve.
•Whileplacingdifferentfractionsonthetable,placethemsomedistanceapartsothatnotwofractionsmaygetmixed.
•Becarefulwhileselectingtheopeningoftheflakinessandelongationgaugesforanyparticularfraction.FlakinessandElongationIndex
FlakinessandElongationIndex
RecommendedValuesofFlakinessIndexandElongationIndex
Limitofflakyparticlesinthemixesis30%.Iftheflakyparticlesaregreaterthan30%thentheaggregateisconsideredundesirablefor
theintendeduse.
Limitofelongatedparticlesinthemixesis45%.Thus,iftheelongatedparticlesaregreaterthan45%,thentheaggregateisconsidered
undesirablefortheintendeduse.

8. Engr. Sayed Shajedul Hasan.
OBSERVATIONS
Sieve size
(mm)
passing
Sieve size
(mm)
retained
Sample weight (g)
A
Weight passing
thickness gauge (g)
B
Weight of non flaky
sample(g)
C
Weightof aggr. retained
length gauge (g)
D
28mm 20mm 2621 692 1929 351
20mm 14mm 1949 261 1688 606
14mm 10mm 735 423 312 101
10mm 6.3mm 32 5 27 20
total 5337 g 1381 g 3956 g 1078 g
CALCULATIONS:
Flakiness Index:Τ��×100= Τ13815337∗100=25.88%
Elongation Index: Τ��∗100= Τ10783956∗100=27.25%
Contained: Flakiness Index+ Elongation Index = 53.13%