SPECIFIC GRAVITY TEST OF BITUMEN

(AASHTO T-228, ASTM D-70)

OBJECT: TO DETERMINE SPECIFIC GRAVITY TEST OF BITUMEN

PERFORMANCE OBJECTIVE:

Upon successful completion of this lab experiment, the student will able to:
 To identify the source of a bituminous binder.
 To estimate mineral impurity in bitumen.

EQUIPMENT:

1. Pyknometre Method:
 Specific gravity bottle of 50 ml capacity, capillary type with 6 mm
diameter neck or wide mouthed capillary type bottle with 25 mm
diameter neck can be used.

2. Balance Method:
 An analytical balance equipped with a pan straddle is used.

DISCUSSION:

The density of the bitumen binder is a fundamental property frequently used as aid in
identifying the binder for use in paving jobs. In most applications the bitumen is weighed,
But finally in use with aggregate system, the bitumen content is converted on volume basis.
Thus an accurate density value is required for conversion of weight to volume.
The specific gravity is greatly influenced by the chemical composition of the binder increased
amount of aromatic type compounds cause an increase in the specific gravity. The specific
gravity of the all types of bituminous materials could be determined by the pyknometer
method. However the bitumen which is semi solid state at 27 oC can be tested by the balance
method. If the bituminous material is in liquid form at 270C, the specific gravity may be
found by the pyknometer method by completely filling the specific gravity bottle with the
liquid material.

Specific Gravity:
“It is the ratio of the mass of a given volume of the bituminous material to the mass of an
equal volume of water, the temperature of both being specified as 270C.”
PROCEDURE:

Pyknometer Method:

1. Clean dry and weigh the specific gravity bottle along with the stopper.

2. Fill the specific gravity bottle with distilled water.

3. Place the stopper.

4. Keep it in water container for at least half an hour at temperature 270C.

5. Remove the bottle and clean it from outside.

6. Weigh the specific gravity bottle containing distilled water.

7. Heat the bituminous material to a poring temperature and pour it in the empty bottle
taking all the precautions that it is clean and dry before filling sample materials.

8. Fill the material up to the half taking care to prevent entry of air bubbles.

9. To permit an escape of air bubbles, the sample bottle is allowed to stand for half an
hour at suitable temperature cooled to 270C and then weigh it.

10. Fill remaining space in the specific gravity bottle with distilled water at 27 0C, place
stopper and place it in water container at 270C.

11. Remove the bottle containing bituminous material and containing water, clean it from
the outside and again weigh it.

Balance Method:

1. Make a cube shaped bitumen specimen about 12 mm on each edge.

2. Prepare it by pouring the liquefied bitumen sample in brass mould to provide the
sample of required dimensions and then it is cooled.

3. Weigh the sample in air and weight it again in the distilled water maintained at 27 oC
to the nearest 0.1 mg.
CALCULATIONS:

Pyknometre Method:

Where,
W1= Weight of empty specific gravity bottle.

W2= Weight of bottle +bitumen.

W3= Weight of bottle +water.

W4= Weight of bottle + water +bitumen.

Balance Method:

Specific Gravity = e/(e-f)

f = weight of the specimen when immersed in distilled water.

Pyknometre Method:
Weight of Weight of Weight of
Sample Weight of bottle + bottle + bottle + water Specific
No: bottle (gm) bitumen water + bitumen Gravity
(gm) (gm) (gm)
01.
02.
03.
Average Value

Balance Method:
Weight of the Weight of the specimen
Sample
dry Specimen when immersed in distilled Specific Gravity
No:
(gm) water (gm)
e f
01.
02.
03.

Average Value
APPLICATIONS:

Specific gravity of the bituminous material is used convert the specified bitumen content by
weight to volume basis when the binder is measured by volume.
Specific gravity is useful to identify the source of a bituminous binder. Higher penetration
grade and cut back bitumen have lower range of specific gravity values.
In case the bitumen contains mineral impurity, the specific gravity will be higher. Thus it is
possible for a qualitative estimation of mineral impurity in bitumen. The specific gravity of
tars depends on the type of carbonization process used for their production.
Vertical-report tars in the range 1.10 to 1.15 whereas horizontal-report and coke oven tars
have values in the range 1.18 to 1.25.

RECOMMENDED VALUES:

The specific gravity of pure bitumen ranges from 0.97 to 1.02. according to Indian Standard
(BIS) minimum specific gravity of paving bitumen at 27°C shall be 0.99 for grades A25,
A35, A45, A65, S35, S45 and S65 , 0.98 for A90 and S90 and 0.97 for A200 and S200.

Review Questions:

1. Define Specific Gravity of bitumen?

2. What is the purpose of Specific Gravity test of bitumen?

3. Give formula for specific Gravity test of bitumen by “Pyknometre Method”?

4. Give formula for specific Gravity test of bitumen by “Balance Method”?

5. Write the applications of Specific Gravity test of bitumen?