Particle size distribution using Andreasen pipette sedimentation technique

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22 Φεβ 2014 (πριν από 3 χρόνια και 8 μήνες)

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Particle size d
istribution using A
ndreasen
p
ipette sedimentation technique

Prasanth Tanikella


Procedure

1.

Fly ash sample



To determine the particle size distribution

of fly
ash,

a 1% solution of fly ash in
water by volume is used with a dispersing agent co
ncentration of 9.8g/l was used. 550 ml of de
-
ionized

water was measured and 5.39 grams of sodium hexa meta phosphate (dispersing agent
SHMP) was mixed with it in a beaker. The solution was prepared by vigorously
dissolving the
SHMP

in the liquid by manual
mixing
. T
he

solution is

then

transferred into the Andreasen
cylinder

and is made
up to

the 20 cm mark
.

Fly ash is

then added to the cylinder

and is again
thoroughly mixed
. This mixing is done by holding the cylinder with both the hands on either
ends, cove
ring the ground in stopper with the index
finger and moving the cylinder by 180
degrees, for 30 seconds. In this process, a few of the liquid might escape from the stopper
,

which might be insignificant. The first sample is taken at time zero as soon as t
he

mixing is done,
which has particles of all sizes and is the initial mass concentration of fly ash.

Aliquots of 10 ml
volume are taken out at different time
intervals, which

correspond to the size of the particle
until

about a day
, wh
ich corresponds to 1 m
icrometer, at a height of 200 mm from the initial
surface of the solution. All the samples are

air

dried

for 30 minutes

and the weights are
measured to find out the cumulative particle size distribution of the fly ash.

This is done by
dividing the mass of
fly ash at a particular time with the initial after correcting for the
concentration of dispersing agent.


2.

Sodium hexa meta phosphate
concentration with time



To determine the concentration of
sodium hexa meta phosphate in the sample,
9.8 g/l of SHMP was
mixed with 550 ml of water.
The solution is prepared by vigorous manual mixing
until

all the crystals of the salt are dissolved
completely. The solution is then shifted to the Andreasen cylinder and 10ml aliquots are taken
in specific time intervals. The s
amples are dried and weighed to determine the concentration of
SHMP in the solution



3.

Sodium hexa meta phosphate in a flask



The concentration of the dispersing agent is measured
directly from the flask by extracting aliquots of 10
ml each

using a pipette
. The samples are dried
to measure the weights. The concentration is determined from the weights.




Results


1.

Petersburg

-

Specific gravity 2.64

-

Amount used in the sample 2.083 grams


Run 1

Run 2

Run 3

Radius

Percentage

Percentage

Percentage

(a)
micrometer
s

Cumulative

Cumulative

Cumulative

100

100

100

100

25

64.61

117.18

94.85

10

66.74

91.72

41.84

5

46.48

-
-

50.11

4

37.1

69.33

40.72

3

29.64

59.2

38.03

1

27.51

75.46

34.45



PSD by pipette analysis









PSD by Boral



PSD by Laser particle size d
istribution


2.

Mill Creek



Run 1

Run 2

Run 3

Radius

Percentage

Percentage

Percentage

(a)
micrometers

Cumulative

Cumulative

Cumulative

100

100

100

100

25

-
63.24

167.32

110.17

10

91.24

118.9

83.9

5

8.01

21.65

58.9

4

6.59

74.02

47.03

3

6.31

64.17

36.4
4

1

4.48

49.61

27.12

PSD by pipette analysis



PSD by Boral












PSD by Laser Particle size distribution



3.

Sodium Hexa

meta phosphate


Concentration of the dispersing agent (Sodium hexa meta phosphate)



Sample

g/liter

1

10.3

2

10.66

3

11.39

4

11.4


Possible reasons for

deviant result
s

1.

The andreasen cylinder has been calibrated and the volume filled up to 20 cm mark is found to
be 544 ml and not 550 ml. This would change the concent
ration of the dispersing agent added
to
9.908 g/l thus chan
ging the entire particle size distribution

2.

The dried samples are not stored in a
desiccator

before weighing, due to which the samples
might

have

adsorb
ed

some water from the atmosphere
, thus

changing the weights and the
cumulative percentages.

3.

A correction

to the decrease in height of the solution in cylinder
,

which is significant enough,

is
to be applied for subsequent samples after the first has been drawn.

4.

More than one sample would be accurate to measure the initial concentration of fly ash.