Flakiness Index and Elongation Index of Coarse Aggregates

Flakiness index and Elongation Index of Coarse Aggregates AIM: i.

to determine the elongation index of the given aggregates

ii.

to determine the flakiness index of the given aggregates

APPARATUS: The apparatus for the shape tests consists of the following: (i) A standard thickness gauge (ii) A standard length gauge (iii) IS sieves of sizes 63 !" #" 3$.! %! %" $6 $%.!$" and 6.3&& (iv) A balance of capacity 5kg, readable and accurate up to 1 gm. THEORY: The particle shape of aggregates aggregates is deter&ined deter&ined ' the percentages percentages of flak and elongated particles contained in it. or 'ase course and construction of 'itu&inous and ce&ent concrete tpes the presence of flak and elongated particles are considered undesira'le undesira'le as these cause inherent weakness with possi'ilities of 'reaking down under  heav loads. Thus evaluation of shape of the particles particularl with reference to flakiness and elongation is necessar. The Flakin Flakiness ess index index of aggr aggrega egates tes is the the perc percent entag age e by weig weight ht of  part partic icles les whos whose e leas leastt dime dimens nsion ion thic thickn kness ess!! is less less than than thre three" e" fift fifths hs #.$ti #.$times mes!! of their their mean mean dimensi dimension. on. This This test is not appli applicab cable le to si% si%es es smaller than $.&mm. The 'longation index of an aggregate is the percentage by weight of  part partic icles les whos whose e great greatest est dime dimens nsion ion len lengt gth! h! is great greater er than than nine" nine"fi fift fths hs 1.(times! their mean dimension. This test is not applicable for si%es smaller than $.&mm. PROCEDURE: i) Sieve the sa&ple through the IS sieves (as specified in the ta'le). ii)Take a &ini&u& of %"" pieces of each fraction to 'e tested and weigh the&. (iii)

In order order to separat separate e the flak flak &aterial &aterials s gauge gauge each fraction fraction for thicknes thickness s on a thickness gauge. The width of the slot used should 'e of the di&ensions specified in colu&n (#) of the ta'le for the appropriate size of the &aterial.

(iv) *eigh the the flak &aterial &aterial passing the gauge gauge to an accurac accurac of at least least ".$ per cent of  of  the test sa&ple.

(v)

In order to separate the elongated &aterials gauge each fraction for length on a length gauge. The width of the slot used should 'e of the di&ensions specified in colu&n (6) of the ta'le for the appropriate size of the &aterial.

(vi) *eigh the elongated &aterial retained on the gauge to an accurac of at least ".$ per  cent of the test sa&ple. Sie of aggregates

*eight *eight

*eight

of 

aggregates

aggregates

fraction

in

in

-etained

consisting

fraction

+ength

fraction

,assing

on

of at least

Thickness

passing

gauge

retained on

through IS

Sieve

%""

gauge size

thickness

size

length

Sieve &&

&&

piecesg

&&

gauge&&

&&

gauge&&

IS

of

of 

each

each

!

"

#

$

%

&

'

63

!"

(!

%3."

)!

/

*

!"

#"

("

%0.""

)"

1$.""

 Y!

#"

3$.!

(#

$.!"

)#

!1.""

 Y"

3$.!

%!

($

$6.!

)$

/

*

%!

%"

(%

$3.!"

)%

#".!

 Y#

%"

$6

(&

$".1"

)&

3%.#

 Y$

$6

$%.!

('

1.!!

)'

%!.!

 Y%

$%.!

$"

(+

6.0!

)+

%".%

 Y&

$"

6.3

(,

#.1

),

$#.0

 Y'

Total

(-

)-

2S4-5ATI2S: lakiness Inde7

-

(8$9 8%9..) ; (*$ 9 *% 9 .) 8 $""

4longation Inde7 <

(= $ 9 =% 9 ) ; (* $ 9 *% 9 .) 8 $""

RESU.T: i) lakiness Inde7

-

 Y -

ii) 4longation Inde7 < RECOMME/DED 0A.UE: The shape tests give onl a rough idea of the relative shapes of aggregates. lak and elongated particles should 'e avoided in pave&ent construction particularl in surface course. If such particles are present in apprecia'le proportions the strength of pave&ent laer would 'e adversel affected due to possi'ilit of 'reaking under  loads. *orka'ilit is reduced for ce&ent concrete. I-> reco&&endations for &a7i&u& li&its of flakiness inde7 are as given.

?a7i&u& Sl o:

Tpe of pave&ent

flakiness inde7 @

$

itu&inous carpet

3"

% (i)

itu&inous ; Asphaltic concrete

(ii)

itu&inous ,enetration &acada& itu&inous surface dressing (single coat two coats  precoated)

  (iii)

Related

li&its

(iv)

uilt up spra grout

3 (i)

itu&inous &acada&

(ii)

*? 'ase course and surface course

%!

$!

Tags:

the effects of flaky and elongated aggregate in road construction, lab experiments shapes in construction, procedure how to test flankeness in soil , conclusion of aggregate shape test flakiness index and elongation index ! for highway construction, flakiness lab procedure, aggregate shape test , flakiness and elongation index test results, flakiness index, elongation index, average least dimension, flakiness and elongation test procedures for aggregates, flakiness and elongation indexes test, aggregate shape test in soil lab, )AA* test,

of