How To Measure Bitumen Content In Mix

Bitumen extraction test is conducted while providing bitumen mixes on the road to ensure the perfect bitumen content in mix & the quality of the mix.

Bitumen content should be examined carefully in each pour of road, the sampling of bitumen mix must be provided from a loaded truck, or a Paver or a freshly laid layer of Road.

Bitumen in the mix is mainly based on the design of pavement, size of aggregates/stones, the client should mention the bitumen content to be poured together with other size aggregates and percentage of each constituent in the mix.

The test is carried out according to IRC: SP 11 –1988 (Appendix - 5) and ASTM D 2172 with centrifuge extractor together with a bowl, filter paper, and solvents like Trichloroethylene or benzene.

The test is conducted in the following manner:-

Trichloroethylene is useful for test because it is non-flammable liquid and contain clear translucent color. At the time of testing, make sure that all necessary types of equipment are easily accessible & in working condition.

Collect a sample of bitumen mix from either laid layer of the road, from paver hopper or directly from a loaded truck. The collected sample should be blended perfectly.

Before pouring the sample in it, it is required to note the weight of the empty bowl but it is not essential in most of the cases. Note the weight of the empty bowl and pour the sample of bitumen mix into the bowl in quantity either 500 grams or 1000 grams or depending on the centrifuge extractor strength.

Make sure that the quantity of weight is perfect with precision to a gram or lessor. It is recommended to obtain 500 or 1000 grams with the nearest sample size devoid of disturbing it.

Once the required sample size in the bowl is obtained, place the bowl in centrifuge extractor.

Also Read: How to estimate the material for a reinforcement concrete road

There is a small hole on its bottom plate through which the mixture of solvent and extracted bitumen is drained out from it. Make sure that the equipment contains mild slope towards the hole for allowing drainage.

Place the bowl in the equipment and include benzene or Trichloroethylene at 200ml per 500 gram sample. Benzene becomes active when it gets in touch with bitumen. Trichloroethylene needs more time for reaction, might be an hour, and may cycle of it.

When the solvent is added, the filter paper should be placed on top of bowl to stop the detachment of finer material from mix due to the gap among the cap and bowl. The weight of filter paper can also be noted before fixing it on top of the bowl.

Once the filter paper is placed, provide a cap on the bowl and tight the nuts perfectly.

Then, place a centrifuge extractor top lid and tighten it to safeguard the cloth and skin against a spray of bitumenous solvent.

The fine materials may come out throughout the process, so it is suggested to place beaker underneath the drain of centrifuge extractor, as soon as the test is finished, examine if any material is accumulated here and include that in the remained mix.

After affixing the top lid, rotate the bowl by revolving the handle. Raise the speed slowly and attain a maximum of 3600 rpm unless no solvent is going out.

Take out the lids and verify the extraction from the mix, when it is eliminated from mix, there will be clear color aggregates in it.

In this phase, the bitumen had removed from mix totally, the aggregates now soak up the solvent so make it dry before obtaining its weight by heating it in the oven at 100 to 110-degree centigrade for an hour. For benzene, cautiously burn it directly to eliminate all the remaining benzene from it.

As soon as the sample is dried in the oven or burnt, take note of the following:-

1. weight of dried sample remains.
2. weight of dried filter paper together with stuck fine material to it.
3. weight of dried fines accumulated in a beaker through the drain.

Finally, the following results are obtained:-

1. weight of sample bitumen mix obtained for the test - 500 or 1000 or recorded value throughout testing -> A.
2. Total weight of dried sample remains after extraction test -> B.

Therefore, the Bitumen content in mix is measured as follow:-
[(A-B) / A] x 100