Understanding Bitumen Content in Asphalt Pavement
The Bitumen Extraction Test serves as a crucial method to ascertain the percentage of bitumen content within asphaltic pavement using the cold solvent extraction technique. This process plays a vital role in determining the properties of flexible pavement, such as durability, compatibility, and resistance to defects like bleeding, raveling, and aging.
Aim of the Test
The primary objective of the Bitumen Extraction Test is to identify the binder content, specifically bitumen, in the asphalt mix through the cold solvent extraction method. This test is instrumental in ensuring the optimal composition of bitumen and aggregate for the construction of durable and resilient pavements.
Code References
The Bitumen Extraction Test adheres to the following code references:
- IRC: SP 11 –1988 (Appendix – 5)
- ASTM D 2172
Required Apparatus
Several essential apparatus are needed for conducting the Bitumen Extraction Test:
- Centrifuge
- Balance: Capacity of 500 grams and sensitivity of 0.01 grams.
- Thermostatically Controlled Oven: With a capacity up to 250°C.
- Beaker: For collecting the extracted material.
Procedure of Test
The Bitumen Extraction Test involves the following detailed steps:
- Take exactly 500 grams of the representative sample and place it in the bowl of the extraction apparatus (W1).
- Add benzene to the sample until it is completely submerged.
- Dry and weigh the filter paper, placing it over the bowl of the extraction apparatus containing the sample (B).
- Clamp the cover of the bowl tightly.
- Place a beaker under the drainpipe to collect the extract.
- Allow sufficient time (not exceeding an hour) for the solvent to disintegrate the sample before running the centrifuge.
- Run the centrifuge slowly, gradually increasing the speed to a maximum of 3600 rpm.
- Maintain the same speed until the solvent ceases to flow from the drainpipe.
- Continue running the centrifuge until both the bitumen and benzene are completely drained out.
- Stop the machine, remove the cover, add 200ml of benzene to the material in the extraction bowl, and repeat the extraction process.
- Repeat the process not less than three times until the extraction is clear and not darker than a light straw color.
- Collect the material from the bowl of the extraction machine along with the filter paper, and dry it to a constant weight in the oven at a temperature of 105°C to 110°C. Cool to room temperature.
- Weigh the material (W2) and the filter paper (D) separately with an accuracy of 0.01 grams.
Calculation and Observation
Use the following table for observation:
Sl No |
Observation |
Sample 1 |
Sample 2 |
Sample 3 |
1 |
Weight of mix before extraction (W1) |
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2 |
Weight of filter paper before extraction (B) |
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3 |
Weight of mix after extraction (W2) |
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4 |
Weight of filter paper after extraction (D) |
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5 |
Weight of filler collected in filter paper (B-D) = W3 |
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The formula to calculate the percentage of binder content is given by:
Percentage of Binder Content=(W3W1)×100Percentage of Binder Content=(W1W3)×100
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