Introduction

This article, on how to calculate a bitumen extraction test, will discuss the procedure for conducting a bitumen extraction test, the equipment required, and the significance of the results. Understanding how to accurately perform and interpret bitumen extraction tests can greatly enhance the quality and longevity of road surfaces.

Bitumen extraction tests are critical in the field of civil engineering and road construction. These tests are performed to determine the amount of bitumen present in asphalt mixtures, which is essential for quality control and ensuring the durability and effectiveness of road surfaces. Bitumen, a binder, holds the aggregate particles together, providing the necessary strength and flexibility to the pavement. Among the various grades of bitumen, 80/100 grade is commonly used for road construction due to its optimal balance of hardness and flexibility.

Equipment Required

To perform a bitumen extraction test, you will need the following equipment:

1.     Centrifuge Extractor: This device is used to separate bitumen from the aggregate.

2.     Solvent: Trichloroethylene or other suitable solvents are used to dissolve the bitumen.

3.     Filter Paper: Used to filter out the aggregate from the dissolved bitumen solution.

4.     Weighing Balance: For measuring the sample and the extracted bitumen.

5.     Oven: For drying the aggregate and bitumen samples.

6.     Sieve Set: For grading the aggregate after bitumen extraction.

7.     Sample Containers: For collecting and storing samples.

Sample Preparation

1.     Collecting the Sample: Obtain a representative sample of the asphalt mixture. The sample size typically ranges from 500 grams to 2000 grams, depending on the project specifications.

2.     Weighing the Sample: Accurately weigh the sample and record its mass.

3.     Drying the Sample: Place the sample in an oven at 110°C to 115°C until it reaches a constant weight. This step removes any moisture present in the sample, ensuring accurate test results.

Test Procedure

1.     Solvent Addition: Place the dried sample into the centrifuge extractor bowl. Add a sufficient amount of solvent (trichloroethylene) to cover the sample completely. The solvent dissolves the bitumen, separating it from the aggregate.

2.     Centrifugation: Secure the extractor bowl in the centrifuge and operate it at the specified speed. The centrifugal force separates the dissolved bitumen from the aggregate.

3.     Filtering the Solution: Pour the solution through filter paper to remove any fine aggregate particles. The filtered solution contains the bitumen dissolved in the solvent.

4.     Evaporating the Solvent: Place the filtered solution in a container and allow the solvent to evaporate, either naturally or by using a low-temperature oven. This step leaves behind the extracted bitumen.

5.     Weighing the Extracted Bitumen: Once the solvent has evaporated completely, weigh the container with the extracted bitumen. Record the weight.

Calculation

The percentage of bitumen in the asphalt mixture is calculated using the following formula:

Percentage of Bitumen=(Weight of Extracted BitumenInitial Weight of Sample)×100\text{Percentage of Bitumen} = \left( \frac{\text{Weight of Extracted Bitumen}}{\text{Initial Weight of Sample}} \right) \times 100Percentage of Bitumen=(Initial Weight of SampleWeight of Extracted Bitumen​)×100

For example, if the initial weight of the sample is 1000 grams and the weight of the extracted bitumen is 50 grams, the percentage of bitumen is:

Percentage of Bitumen=(501000)×100=5%\text{Percentage of Bitumen} = \left( \frac{50}{1000} \right) \times 100 = 5\%Percentage of Bitumen=(100050​)×100=5%

Aggregate Analysis

After the bitumen extraction, the remaining aggregate should be thoroughly washed with solvent to remove any residual bitumen. The washed aggregate is then dried and sieved to determine its gradation. This analysis helps in assessing the quality and composition of the aggregate used in the asphalt mixture.

Significance of Results

The results of the bitumen extraction test provide valuable information about the asphalt mixture:

• Quality Control: Ensures that the bitumen content is within the specified range for optimal performance.
• Mix Design Verification: Confirms that the mix design parameters are being met during production.
• Pavement Performance: Adequate bitumen content contributes to the durability, flexibility, and resistance to deformation of the pavement.
• Adjustment of Mix: If the bitumen content is found to be too high or too low, adjustments can be made to the mix design to achieve the desired properties.

Reference to Bitumen 80/100

Bitumen 80/100 is a common grade used in asphalt mixtures due to its desirable properties. It has a penetration value between 80 and 100, indicating its medium hardness and ability to provide a balance between flexibility and durability. During the bitumen extraction test, it is essential to ensure that the bitumen 80/100 content is within the specified range to maintain the performance characteristics of the pavement. Excessive or insufficient bitumen content can lead to pavement failures such as rutting, cracking, or stripping.

Conclusion

The bitumen extraction test is a crucial procedure in the field of civil engineering, ensuring the quality and performance of asphalt pavements. By accurately determining the bitumen content in asphalt mixtures, engineers can make informed decisions regarding mix design adjustments and quality control measures. The use of bitumen 80/100 in road construction highlights the importance of selecting the right grade of bitumen for achieving the desired pavement properties. Properly conducted bitumen extraction tests contribute to the construction of durable, flexible, and long-lasting road surfaces, enhancing the overall infrastructure.