07 January 2014
Bitumen is a mixture of organic liquids that is black, highly viscous, sticky product used for paving roads, waterproofing products (used in sealing roofs). There are many tests which are conducted to check the quality of bitumen. Bitumen is very important component of many construction sites like roads, highways. Many tests are done to ensure the quality of bitumen. Some of these are given below :-
1. Bitumen Content 2. Ductility Of Bitumen 3. Penetration of Bitumen 4. Specific Gravity of Bitumen 5. Softening Point Of Bitumen 6. Flash And Fire Point Of Bitumen 7. The Marshall Stability of Bituminous Mixture
BITUMEN CONTENT This test is done to determine the bitumen content as per ASTM 2172. The apparatus needed to determine bitumen content are - i) Centrifuge extractor ii) Miscellaneous – bowl, filter paper, balance and commercial benzene. A sample of 500g is taken.
Procedure to determine bitumen content i) If the mixture is not soft enough to separate with a trowel,place 1000g of it in a large pan and warm upto 100oC to separate the particles of the mixture uniformly.
ii) Place the sample (Weight ‘A’) in the centrifuge extractor. Cover the sample with benzene, put the filter paper on it with the cover plate tightly fitted on the bowl.
iii) Start the centrifuge extractor, revolving slowly and gradually increase the speed until the solvent ceases to flow from the outlet.
iv) Allow the centrifuge extractor to stop. Add 200ml benzene and repeat the procedure.
v) Repeat the procedure at least thrice, so that the extract is clear and not darker than the light straw colour and record the volume of total extract in the graduated vessel.
vi) Remove the filter paper from the bowl and dry in the oven at 110 + 5oC. After 24hours, take the weight of the extracted sample (Weight ‘B’).
REPORTING OF RESULTS Bitumen content = [(A-B)/B]×100 % Repeat the test thrice and average the results.
Determining the Ductility Of Bitumen ***************************************
This test is done to determine the ductility of distillation residue of cutback bitumen, blown type bitumen and other bituminous products as per IS: 1208 – 1978. The principle is : The ductility of a bituminous material is measured by the distance in cm to which it will elongate before breaking when a standard briquette specimen of the material is pulled apart at a specified speed and a specified temperature.
The apparatus required for this test: i) Standard mould ii) Water bath iii) Testing machine iv) Thermometer – Range 0 to 44oC, Graduation 0.2oC
Procedure to determine the Ductility Of Bitumen i) Completely melt the bituminous material to be tested by heating it to a temperature of 75 to 100oC above the approximate softening point until it becomes thoroughly fluid. Assemble the mould on a brass plate and in order to prevent the material under test from sticking, thoroughly coat the surface of the plate and the interior surfaces of the sides of the mould with a mixture of equal parts of glycerine and dextrin. While filling, pour the material in a thin stream back and forth from end to end of the mould until it is more than level full. Leave it to cool at room temperature for 30 to 40 minutes and then place it in a water bath maintained at the specified temperature for 30 minutes, after which cut off the excess bitumen by means of a hot, straight-edged putty knife or spatula, so that the mould is just level full. ii) Place the brass plate and mould with briquette specimen in the water bath and keep it at the specified temperature for about 85 to 95 minutes. Remove the briquette from the plate, detach the side pieces and the briquette immediately.
iii) Attach the rings at each end of the two clips to the pins or hooks in the testing machine and pull the two clips apart horizontally at a uniform speed, as specified, until the briquette ruptures. Measure the distance in cm through which the clips have been pulled to produce rupture. While the test is being done, make sure that the water in the tank of the testing machine covers the specimen both above and below by at least 25mm and the temperature is maintained continuously within ± 0.5oC of the specified temperature.
REPORTING OF RESULTS A normal test is one in which the material between the two clips pulls out to a point or to a thread and rupture occurs where the cross-sectional area is minimum. Report the average of three normal tests as the ductility of the sample, provided the three determinations be within ± 0.5 percent of their mean value.
If the values of the three determinations do not lie within ± 0.5 percent of their mean, but the two higher values are within ± 0.5 percent of their mean, then record the mean of the two higher values as the test result. This test is done to determine the penetration of bitumen as per IS: 1203 – 1978. The principle is that the penetration of a bituminous material is the distance in tenths of a mm, that a standard needle would penetrate vertically, into a sample of the material under standard conditions of temperature, load and time. The apparatus needed to determine the penetration of bitumen is
i) Penetrometer
ii) Water bath
iii) Bath thermometer – Range 0 to 44oC, Graduation 0.2oC
SAMPLE Bitumen should be just sufficient to fill the container to a depth of at least 15mm in excess of the expected penetration.
Procedure to determine the penetration of bitumen i) Soften the bitumen above the softening point (between 75 and 100oC). Stir it thoroughly to remove air bubbles and water.
ii) Pour it into a container to a depth of at least 15mm in excess of the expected penetration.
iii) Cool it at an atmospheric temperature of 15 to 30oC for 11/2 hours. Then place it in a transfer dish in the water bath at 25.0 + 0.1oC for 11/2 hrs.
iv) Keep the container on the stand of the penetration apparatus.
v) Adjust the needle to make contact with the surface of the sample.
vi) Adjust the dial reading to zero.
vii) With the help of the timer, release the needle for exactly 5 seconds.
viii) Record the dial reading.
ix) Repeat the above procedure thrice.
REPORTING OF RESULTS The value of penetration reported should be the mean of not less than three determinations expressed in tenths of a mm.
This test is done to determine the specific gravity of semi-solid bitumen road tars, creosote and anthracene oil as per IS: 1202 – 1978. The principle is that it is the ratio of mass of a given volume of bitumen to the mass of an equal volume of water, both taken at a recorded/specified temperature. The apparatus needed to determine specific gravity of bitumen is
i) Specific gravity bottles of 50ml capacity ii) Water bath iii) Bath thermometer – Range 0 to 44oC, Graduation 0.2oC Take the sample (half the volume of the specific gravity bottles).
Procedure to determine specific gravity of bitumen i) Clean, dry and weigh the specific gravity bottle along with the stopper (Weight ‘A’).
ii) Fill the specific gravity bottle with freshly boiled distilled water and insert the stopper firmly. Keep it in the water bath having a temperature of 27.0 + 1oC for not less than half an hour and weigh it (Weight ‘B’).
iii) Weigh the specific gravity bottle about half-filled with the material (Weight ‘C’).
iv) Weigh the specific gravity bottle about half-filled with the material and the other half with distilled water (Weight ‘D’).
v) Weigh the specific gravity bottle completely filled with the material (Weight ‘E’).
REPORTING OF RESULTS i) Specific gravity (Solids and semi-solids) = (C-A )/[ ( B-A) - (D-C)] ii) Specific gravity (Liquids) = (E-A)/(B-A) The average of the two results should be reported.
CAclubindia
