FLAKINESS INDEX OF AGGREGATE
OBJECTIVE
For determination of flakiness index
of coarse aggregate, where the size of the coarse aggregate are larger
than 6.3 mm .
REFERENCE STANDARDS
IS : 2386 (Part I) – 1963 – Method
of test for aggregates for concrete (Part I) Particle size and shape.
EQUIPMENT & APPARATUS
§ Thickness gauge
§ Sieves [63, 50, 40, 31.5, 25, 20, 16, 12.5, 10 & 6.3 mm]
§ Balance [0-10 kg]
Fig:-Showing Thickness Gauge
PREPARATION SAMPLE
Surface dry samples is used for the
test. A minimum number of 200 pieces of any specified fraction is required to
do the test.
PROCEDURE
1.
The sample is sieved through IS
sieve specified in Table shown below
2.
A minimum of 200 pieces of each
fraction is taken and weighed.
3.
In order to separate flaky
materials, each fraction is then gauged individually for thickness on a
thickness gauge.
4.
The total amount of flaky material
retained by the thickness gauge is weighed to an accuracy of 0.1% of the weight
of sample.
Table:-Grading of Aggregate
|
Passing
IS Sieve
|
Retained
On IS Sieve, mm
|
Weight
of IS Sieve fraction W1, g
|
Proportion
of size range in the sample, 100 W1/W, %
|
|
63
|
50
|
W1=
|
100 W1/W=X1
|
|
50
|
40
|
W2=
|
100 W2/W=X2
|
|
40
|
31.5
|
|
|
|
31.5
|
25
|
|
|
|
25
|
20
|
2680
|
19.47
|
|
20
|
16
|
5170
|
37.56
|
|
16
|
12.5
|
4110
|
29.86
|
|
12.5
|
10
|
1465
|
10.64
|
|
10.0
|
6.3
|
336
|
2.44
|
|
TOTAL
|
|
£W1=W=13761
|
100£x1=100%
|
table:-Proportion of Flaky
Aggregate
|
Size
range of Aggregates, passing & retaining IS Sieve size, mm
|
Weight
of 200 pieces of aggregates of range, gm
|
Thickness
gauge size, mm.
|
Weight
of flaky particles, gm
|
Percentage
by wt, of flaky aggregate, 100*f/p=y, %.
|
Wt
%. of flaky participles' = XY
|
|
63-50
|
p1 =
|
23.90
|
f1=
|
100f1/p1=y1=
|
x1y1=
|
|
50-40
|
p2=
|
27.00
|
f2=
|
y2=
|
x2y2=
|
|
40-31.5
|
|
21.50
|
|
|
|
|
31.5-25
|
|
16.95
|
|
|
|
|
25-20
|
2448
|
13.50
|
573
|
23.4
|
455.6
|
|
20-16
|
1558
|
10.80
|
410
|
26.3
|
987.8
|
|
16-12.5
|
854
|
8.55
|
227
|
26.58
|
793.7
|
|
12.5-10
|
400
|
6.75
|
134
|
33.5
|
356.4
|
|
10-6.3
|
195
|
4.89
|
45.5
|
23.33
|
56.8
|
|
|
£p1=p=
|
|
|
£y1=
|
f1=£x1y1=2650/100=26.50
|
CALCULATION
In order to calculate the flakiness
index of the entire sample of aggregates, first the weight of each fraction of
aggregate passing and retained on the specified set of sieves is noted (Y1, Y2,
Y3, Y4…..etc). Each piece of these are tried to be passed through the slot of
the specified thickness of the thickness gauge are found and weighed (y1, y2,
y3, y4…etc). Then the flakiness index is the total weight of the material
retained on the various thickness gauges, expressed as a percentage of the
total weight of the sample gauged.
RESULT
Flakiness index is reported in
percentage to the nearest whole number
SAFETY & PRECAUTIONS
§ Use hand gloves while removing containers from oven after
switching off the oven.
§ Use safety shoes, mask & aprons at the time of test.
§ Thoroughly clean & dry the container before testing.
§ Special care should be taken that no outer air enters when
using the balance.
§ All parts of the equipment should always be kept clean.
§ After the end of the test sieve should be clean by smooth
brush.
NICE
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