Test of Bitumen
Composition test and uses for pavement
construction with aparatus, procedure
Composition test of Bitumen
Composition gives the composition of different volatile, non-volatile and inner materials etc
in the bitumen. The test is carried out for following:
A) Distillation test:-
It is used to determine the quantity and quality of volatile constituents and the amount of
non-volatile residues present in bitumen.
The relative proportion of bitumen and volatiles present in the bitumen or cutback is
determined by Distillation test.
It also measures the amount of volatiles driven off at certain specified temperatures. The
residue bitumen is tested for penetration, ductility , and solubility.
Fig1. distilation test set up
Equipment used for Distillation test:
Distillation flask with cork and thermometers etc. as shown in Fig.
Procedure for Distillation test:
1. The sample of the material is put into the flask and the specified thermometer is inserted.
2. The sample is heated and the condensed product collected and measured as shown in Fig.
B) Water content Test:
It’s conducted to determine the water content of bitumen . The specimen is mixed with pure
petroleum distillate free from water and heated that distills up the water . The condensed
water is collected and expressed as % of weight of original sample. Maximum water content
is not greater than 0.2% by weight.
Water present in the bitumen , forms foams of bitumen when heated above 100 oC . Thus
water content in bitumen should be minimum.
Procedure for water content test
1. The known weight of bitumen is mixed in a pure petroleum distillate free from water.
2. The solution is heated and distilled.
3. The weight of distilled water is found and expressed as percentage of original weight
of sample.
4. The maximum water content in bitumen should not exceed more than 0.2% by weight.
C) Loss on heating test:
It’s used to determine the amount of volatile materials present in the bitumen. 50 gm of
sample is taken and heated for 5 hrs in special oven @ temperature of 163 oC. The result is
weighted and loss of weight is calculated as % of original weight.
The loss on heating is not greater than 1 %.
When bitumen heated, it drives off the volatiles and gets hardens. Thus it losses in weight.
Thus the loss in weigth of bitumen is determined as follows:
1. About 50 gram sample of bitumen is taken and weighted accurately.
2. Now the sample of bitumen is heated at 163oC for 5 hours in a specified oven designed for
this test as per I.S. 1212-1958.
3. The specimen is weighted again after heating and loss in weight is determined.
4. The loss of weight is expressed as pwercentage of the original weight. This should not be
more than 1 % for bitumen.
D) Solubility test
This test determines the present of inert materials, carbons, salts etc. in bitumen.
Pure bitumen is completely soluble in carbon disulphide(C2s) and carbon tertra
chloride(CCl4). Hence any impurity in the bitumen can be determined by dissolving the
bitumen in any of the above solvents.
Hence 2 gm of bitumen is taken and dissolved in 100 ml of solvent (C2s or CCl4). The
solution is filtered and resisue is washed , dried and weighted. The % of insoluble materials
w.r.t. original sample in no case should exceed 1 %.
Procedure for solubility test
1. A sample of about 2 gram of bitumen is dissolved in about 100 c.c. of solvent.
2. The solution is filtered and the residue is washed, dried and weighted.
3. Solubility is expressed as percentage of original sample. The insoluble matter should
be prefably less than 1 % in carbon disulphide.
4. If carbon tetrachloride is used as solvent, and the black carbonaceous residue is more than
0.5% then the bitumen is called to be cracked.
E) Spot Test
This test is used to determine the over heated or cracked bitumen . This test is considered
more sensitive than the solubility test for detection cracking.
Procedure:
2 gm of bitumen is mixed with 10 ml of Nepthalene. From the solution , first drop is taken
after 1 hr. of solution preparation and placed in filter paper and same thing is done after
24 hrs .
If the strain of spot has uniform colour, it means uncracked bitumen . But, if the strain forms
annular ring thick brown or black at center and faint at periphery, it’s over-heated or
cracked.
F) The Swell Test
This test is conducted for asphalt mix pavements. This test is carried out to determine the
possible detrimental effects of water on the pavements.
Fig2. Swell test set up
Equipment:
The test set up is shown in Fig.
Procedure for Swell test
1. A sample of the bitumen mix is compacted in a metal cyclinder of 10 cm internal diameter
and cooled to room temperature.
2. The specimen along with mould is put in a pan of water and a dial guage assembly is
mounted above it as shown in Fig.
3. The swell of specimen on absorption of water from the pan is indicated by the dial guage.
