Shape tests of aggregate for highway material construction. it includes Flakiness Index,Elongation Index and Angularity Number

1. SHAPE TESTS
OF
AGGREGATE

2. Prepared by
Name Roll no
1. Jessica lamichane 72046
2. Jitendra Yadav 72047
3. Kisahan ojha 72048
4. Krishna kamal sah 72049
5. Lila regmi 72050

3. IMPORTANCE OF SHAPE OF COARSE AGGREGATE
The shape of aggregate particle is determined by the percentage of flaky and elongated particles
contained on presence of Flaky and elongate particles in the coarse aggregate used for base and
Surface courses of road pavement is considered undesirable, as these may cause inherent weakness
with possibilities of breaking down during compaction as well as under heavy traffic load.
The shape test are mechanical measure of particle shape which may be included in the specification for
aggregate for road construction. These are the flakiness index elongation index and angularity number,
1. Flakiness index
Flakiness index of aggregate is the percentage by weight of aggregate
particles the least dimension of which is less 0.6 of their mean dimension. The
test is applicable to sizes larger than 6.3mm.
 Apparatus
I. Thickness gauge
II. IS sieves

5. PROCEDURE
 The sample of aggregate to be tested is first sieved through a set of sieve
and separated into specified size ranges.
 Separate the flaky material of aggregate which pass through the
appropriate slot pf the thickness gauge.( The slot length and size are
shown in table below for different sieve)

6. Observation and calculation
 If the selected size range in a group is 20-16mm sieve (i.e. passing through
20mm and retain om 16mm sieve)
The width of the slot must be =
(20+16)
2
∗ 0.6
=10.8mm
Flaky index =
𝑤1∗100
𝑤
Where,
w1= the flaky material passing the appropriate slot from each size range of
aggregate
W2= total weight of sample

7. RESULT:
the flaky index was found to be …….........
Recommendation
The IRC suggest that the FI of aggregate used in bituminous concrete and surface
dressing should not exceed 25%; the aggregate used in water bound macadam and
bituminous Macadam should not exceed 15%.

8. ELONGATION INDEX
Objective:
 To determine the elongation index of coarse aggregate
Apparatus
1. Balance
2. Metal gauge
3. IS Sieves
4. Sample of aggregate (a quantity of aggregate shall be taken sufficient to
provide a minimum no of 200 pieces od any fraction to be tested.)

10. Theory
The elongation index on an aggregate is the percentage by weight of particles whose
greatest dimension (length) is greater than 1.8 times their mean dimension. The elongation
index is not applicable to sizes smaller than 6.3 mm.
PROCEDURE
 Sieving
The sample shall be Sieved through all the sieves mentioned starting from the largest sieve
i.e. 63mm.
 Separation of elongation material
Separate all the individual fractions – 63mm to 50mm, 50mm to 40mm, 40mm to 25mm,
25mm to 20mm, 20mm to 16mm. 16mm to 12.5mm. 12.5mm to 10mm and 10mm to
6.3mm.
 Weighing of elongated material
Weigh the particles retained on length gauge

11. Observation and calculation
 Weight of elongated material : w1
 Total weight of sample :w2
elongated index =
𝑤1
𝑤2
∗ 100
Result
The elongation index was found to be………….

12. Recommendation
 The elongation index greater than 15%are generally considerd
undesirable.

13. 3.Angularity number
 Objective
To determine the angularity no of the given sample of aggregate
 Theory :
The angularity no of aggregate is the amount to the nearest whole number by
which the percentage of voids exceeds 33 when an aggregate is compacted in
a specific manner in a standardized metal cylinder
 Significance of test
 The degree of packing of particles of single sized aggregate depends upon
the angularity of aggregate.
 The angularity of the aggregate can be estimated from the properties of
voids in a sample of aggregate compacted in a specified manner.

14.  The angularity number ranges from 0 for a highly rounded grave to about 11
for freshly crushed angular aggregates.
 Higher the angularity number, more angular and less workable is the concrete
mix.
 In cement concrete roads (rigid pavements) rounded aggregates are preferred
because of better workability and higher strength.
 In bituminous or water bound macadam construction (like flexible pavements),
angular aggregates with high angularity number are preferred because of high
stability due to better interlocking and friction.
 Higher the angularity number, more angular and less workable is the concrete
mix.
 In road construction, angularity number of 7 -10 is generally preferred

15. Apparatus
metal cylinder (3lit capacity)
temping rod(16mm and 60cm length)
balance

16. Procedure
 The certain weight of the sample aggregate was taken (The material
should be oven dried)
 The metal cylinder was filled with 3 layer each layer being tamped 100
times with tamping rod.
 The cylinder was emptied and weight of aggregate was taken.
 Cylinder filled with water and the weight of water was determined
 The sp. Gravity of the aggregate can separatly determined

17. Observation and calculation
 W1= weight of aggregate on the cylinder
 W= weight of water
G= Sp. gravity of aggregate
AN= 67 -
𝑊1∗100
𝑊

18. RESULLT:
The angularity number of sample aggregate found to be……………
 Recommendation
More angular is the aggregate should be its higher angularity
number . Angularity number of good aggregate should lies
between 0-10. since the soft aggregate get crushed during
compaction, the angularity number cannot be applied to the
aggregate which get crushed during the test.

19. THANK YOU