Composition test of Bitumen
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.
Equipment used for Distillation test:
Distillation flask with cork and thermometers etc. as shown in Fig.
Procedure for Distillation test:
- The sample of the material is put into the flask and the specified thermometer is inserted.
- 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
- The known weight of bitumen is mixed in a pure petroleum distillate free from water.
- The solution is heated and distilled.
- The weight of distilled water is found and expressed as
percentageof originalweight of sample.
- The maximum water content in bitumen should not exceed more than 0.2% by weight.
C) Loss on
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:
50 gramsample of bitumen is taken and weighted accurately.
- 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.
- The specimen is weighted again after heating and loss in weight is determined.
- The loss of weight is expressed as
pwercentageof 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
- A sample of about 2 gram of bitumen is dissolved in about 100 c.c. of solvent.
- The solution is filtered and the residue is washed, dried and weighted.
- Solubility is expressed as
percentageof originalsample. The insoluble matter should be prefablyless than 1 % in carbon disulphide.
- 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.
2 gm of bitumen is mixed with 10 ml of
If the strain of spot has
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.
The test set up is shown in Fig.
Procedure for Swell test
- A sample of the bitumen mix is compacted in a metal
cyclinderof 10 cm internal diameter and cooled to room temperature.
- The specimen along with
mouldis put in a pan of water and a dial guageassembly is mounted above it as shown in Fig.
- The swell of
specimenon absorptionof water from the pan is indicated bythe dial guage.