The penetration value test is utilized to measure the hardness or consistency of bituminous material, such as asphalt. The test determines the vertical distance penetrated by a standard needle point into the bitumen under specific conditions of temperature, load, and time. The measurement is taken in tenths of a millimeter. An 80/100 grade bitumen signifies that its penetration value falls between 80 and 100.
The primary purpose of the penetration test is to evaluate the consistency of bituminous material. However, it is not suitable for testing road tar due to its high surface tension. This test is used to determine the suitability of bitumen for various types of construction and different climatic conditions.
In conclusion, the penetration test is a useful tool for measuring the hardness or consistency of bituminous material, and it provides important information about the suitability of bitumen for various construction projects and environmental conditions. However, it is not suitable for testing road tar due to its unique properties.
Determination of Penetration Value of Bitumen
Apparatus for Penetration Test
Container
A metallic dish with a flat bottom and cylindrical shape is needed. The dish should have a diameter of 55 mm and a depth of 35 mm. However, if the penetration is equal to or greater than 225, a larger dish is required. The larger dish should have a diameter of 70 mm and a depth of 45 mm.
Needle
The object in question is a cylindrical rod made of hard steel. It is straight and has a highly polished surface. The rod has a smooth and uniform appearance due to its polished finish. The steel material used to create the rod is known for its durability and strength, making it a sturdy and reliable tool. With its cylindrical shape, the rod has a constant diameter throughout its length, which provides consistency in its use. Overall, this steel rod is a well-crafted and robust tool that is suitable for a variety of applications.
Water bath
A water bath is specified to be used in a manner where it is maintained at a temperature of 25° ± 0.1°C. The bath should contain at least 10 litres of water, and the sample being tested must be fully immersed in the water to a depth no less than 100mm from the top. Furthermore, the sample must be placed on a perforated shelf that is positioned no less than 50mm from the bottom of the bath. These specifications are important for ensuring accurate and consistent results in experiments and tests that require the use of a water bath.
Transfer dish or tray
To ensure the accuracy of the test results, the support provided to the container should be stable and secure, without causing any movement or shaking during the testing process. Additionally, the capacity of the support should be sufficient to fully submerge the container being tested. This is necessary to ensure that the testing conditions are consistent and reliable. By maintaining a stable and properly-sized support system, the testing process can be conducted with confidence, allowing for accurate and precise results.
Penetration apparatus
The design of the instrument should enable the needle to penetrate with minimal friction, while also ensuring that it is precisely calibrated to provide measurements with an accuracy of one-tenth of a millimeter.
Thermometer
The range of the temperature measurement is between 0 to 44 degrees Celsius, and the device is capable of reading the temperature up to an accuracy of 0.20 degrees Celsius. This means that the device can detect even minor changes in temperature within the given range, providing precise and accurate readings. It is important to note that the temperature readings are only valid within this range, and the device may not provide accurate readings outside of this range. Therefore, it is necessary to use the device within the specified temperature range to ensure accurate temperature measurements. Additionally, the level of accuracy provided by the device makes it suitable for a variety of applications where precise temperature measurements are required.
Time measuring device
With an accuracy of l second.
Procedure for Bitumen Penetration Test
The first step in conducting this test is to prepare the test specimen. For tars, the material should be softened to a pouring consistency at a temperature no higher than 60°C, while for bitumen, the temperature should not exceed 90°C above the approximate softening point. The softened material should then be thoroughly stirred until it is homogeneous, free from air bubbles and water, and poured into a container to a depth of at least 10mm above the expected penetration. The sample should be protected from dust and allowed to cool in an atmosphere between 15°C to 30°C for one hour before being placed in the water bath at 25°C ± 0.1°C, unless otherwise specified.
Next, fill the transfer dish with water from the water bath to a depth sufficient to completely cover the container, place the sample in it, and put it on the stand of the penetration apparatus.
To prepare the needle for testing, it should be cleaned with benzene, dried, and loaded with the weight. The total moving load, including the weight of the needle, carrier, and super-imposed weights, should be 100 ± 0.25 gms.
The needle should be adjusted to make contact with the surface of the sample. This can be done by placing the needlepoint in contact with its image reflected by the surface of the bituminous material. The pointer of the dial should be made to read zero, or the initial dial reading should be noted.
To begin the test, release the needle for exactly five seconds. The penetration machine should be adjusted to measure the distance penetrated, and at least three readings should be taken at points on the surface of the sample that are not less than 10mm apart and not less than 10mm from the side of the dish. After each test, the sample and transfer dish should be returned to the water bath, and the needle should be washed clean with benzene and dried.
If the material being tested has a penetration greater than 225, three determinations on each of the two identical test specimens using a separate needle for each determination should be made. The needle should be left in the sample on completion of each determination to avoid disturbance of the specimen.
Precautions during Penetration Test
To ensure accurate and precise results, it is crucial that the container remains still while the needle penetrates into the sample. Even the slightest movement can cause errors in the measurement, leading to inaccurate results. Therefore, it is important to handle the container with care and avoid any unnecessary disturbances during the process.
Moreover, the sample must be pure and free from any external matter that may affect the test results. Any contamination or impurities in the sample can lead to inaccurate readings, compromising the validity of the analysis. Hence, it is essential to take necessary precautions and ensure the sample is clean before proceeding with the testing.
In addition, the needle used for penetration must be thoroughly cleaned with benzene and dried before use. This is to ensure that any residual substances on the needle do not affect the sample or the accuracy of the test. By following these procedures, one can obtain reliable and consistent results, making the testing process more efficient and effective.
Observations for Penetration Test
Actual test temperature = °C
| Penetration dial reading | Test 1 | Test 2 | Test 3 |
| (a) Initial | |||
| (b) Final | |||
| Penetration Value |
Result of Test
Mean Penetration Value =
Recommended Penetration Value of Bitumen
Penetration testing is a commonly used method to assess the hardness of bitumen. This testing involves measuring the depth to which a standard needle penetrates the bitumen sample under specific conditions. The resulting value is used to assign a grade to the bitumen, with the 80/100 grade indicating a penetration value between 80 and 100.
The grading of bitumen is an essential step in evaluating its suitability for various construction projects and different climatic conditions. The Indian Road Congress (IRC) recommends the use of bitumen grades 30/40, 60/70, and 80/100 for bituminous macadam and penetration macadam.
In warmer regions, lower penetration grades are preferred as they are less likely to soften in high temperatures. In contrast, higher penetration grades, such as 180/200, are more suitable for colder regions to prevent the bitumen from becoming excessively brittle. In spray application works, high penetration grades are typically used.
Overall, grading bitumen is crucial in ensuring its performance and longevity in various environments and construction applications. The appropriate grade of bitumen can help ensure that the material will withstand the demands of the project and the surrounding conditions.