Determination of Flakiness and Elongation Index For The Given Aggregate Sample.

EXPERIMENT 1
DETERMINATION OF THE FLAKINESS AND THE ELONGATION INDEX FOR THE

GIVEN AGGREGATE SAMPLE.
SCOPE & SIGNIFICANCE

This test is used to determine the particle shape of the aggregate and each particle shape being
preferred under specific conditions.
The significance of flakiness & elongation index is as follows;
 The degree of packing of the particles of one size depends upon their shape.
 Due to high surface area to volume ratio, the flaky and elongated particles lower the
workability of concrete mixes.
 Flaky and elongated particles are considered undesirable for base coarse construction as
they may cause weakness with possibilities of braking down under heavy loads.
 BS-1241 specifies a Flakiness index not exceeding 30% irrespective of the aggregate
size.
 Maximum permitted Elongated index is 35, 40 or 45% for aggregate sizes 2 ½’’ – 2’’,
1 ½’’ – ¾’’ & ½’’ – 3/8’’.
 Both Flakiness and Elongation tests are not applicable to sizes smaller then 6.3mm i.e.
¼’’ sieve.
RELATEDTHEORY
SHAPES OF PARTICLES
The usual shapes of the particles are;

 Rounded (river gravel) Flakiness and Elongation Index
 Flaky (laminated rock) Flakiness and Elongation Index
 Elongated Flakiness and Elongation Index
 Angular( crushed rock)
PREFERRED USE OF EACH SHAPE

 Rounded aggregates are preferred in concrete roads (rigid pavements) as the workability
of concrete increases due to the less friction between the surfaces.
 Angular shape of the particles is desirable in granular base coarse (flexible pavement)
due to better interlocking and increased stability.
 Flaky and Elongated particles are considered as a source of weakness.
HUMA ALI 2016-CIV-65

FLAKY PARTICLES
Flaky particles are those whose least dimension is 0.6 times lesser than the mean size. Thickness
of these particles are comparatively smaller than the other two dimensions. Maximum allowable
limit of the flaky particles in the mix is 30%. If it exceeds this value then the mix is considered
unsuitable for construction purpose.
FLAKINESS INDEX
It is the percentage by weight of flaky particles in a sample. The flakiness Index is calculated by
expressing the weight of flaky particles as a percentage of the total weight of the sample.
ELONGATED PARTICLES
These are the particles having length considerably larger than the other two dimensions. OR
These are the particles whose one dimension is 1.8 times greater than the other two dimensions.
Maximum allowable limit of the flaky particles in the mix is 30%. If it exceeds this value then
the mix is considered unsuitable for construction purpose.
ELONGATION INDEX
It is the percentage by weight of elongated particles in a sample. The elongated Index is
calculated by expressing the weight of elongated particles as a percentage of the total weight of
the sample.
APPARATUS
 Thickness/Flakiness Index Gauge.

 Length/Elongation Index Gauge.
 Aggregate sample to be tested.
 Coarse Sieve Shaker
 Weighing Balance

TEST PROCEDURE
 Perform the sieve analysis on the given aggregate sample

 The aggregates are then arranged in the into a number of closely limited particle size
groups -stored on the test sieves into a number of closely limited particle size groups – 2
½’’ – 2’’, 1 ½’’ – ¾’’ & ½’’ – 3/8’’
 Each group (fraction) is weighed and tested for thickness on appropriate opening of the
thickness gauge by passing each particle through slot of specified thickness along least
dimension.
 The weight of particles passing the thickness gauge is recorded for each fraction. This is
the weight of flaky particles.
 The flakiness index is calculated by expressing the weight of flaky particles as a
percentage of total weight of the sample.
OBSERVATIONS AND CALCULATIONS
PRECAUTIONS
 While sieving, care must be taken that the particles that are chocked in the sieve must
no be forced down into the next sieve. Such particles should be pushed back into the
same sieve.
 While placing different fractions on the table, place them some distance apart so that
no two fractions may get mixed.
 Be careful while selecting the opening of the flakiness and elongation gauges for any
particular fraction.
RECOMMENDATIONS FOR FLAKINESS AND ELONGATION INDICES
The shape tests give only a rough idea of the relative shapes of aggregates. Flaky and elongated
particles should be avoided in pavement construction, particularly in surface course. If such
particles were present in appreciable proportions, the strength of pavement layer would be
adversely affected due to possibility of breaking under loads. Workability is reduced for cement
concrete
.
REFERENCES

https://www.academia.edu/37842758/Determination_of_the_Flakiness_and_the_Elongation_Ind
ex_for_the_Given_Aggregate_Sample
https://civilengineerspk.com/transportation-engineering-experiments/exp-1-flakiness-and-
elongation-index/

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EXPERIMENT 1

DETERMINATION OF THE FLAKINESS AND THE ELONGATION INDEX FOR THE

SCOPE & SIGNIFICANCE

The usual shapes of the particles are;

PREFERRED USE OF EACH SHAPE

HUMA ALI 2016-CIV-65

 Thickness/Flakiness Index Gauge.

HUMA ALI 2016-CIV-65

 Perform the sieve analysis on the given aggregate sample

OBSERVATIONS AND CALCULATIONS

RECOMMENDATIONS FOR FLAKINESS AND ELONGATION INDICES

HUMA ALI 2016-CIV-65

HUMA ALI 2016-CIV-65

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