Penetration Bitumen
One of the important characteristics of bitumen is its temperature change, and penetration index is used to detect and evaluate this characteristic. To determine the penetration of bitumen, two tests of penetration degree and softness degree (softness point) are used.The change of bitumen from solid to liquid during the addition of temperature does not take place and is done in a small way. The duration of its conversion from solid to liquid is different for different bitumen. For example, bitumens that have the same degree of penetration at 25 ℃, it is possible that they have different hardness at higher temperatures, and therefore it is necessary to determine the temperature for them.
For example, bitumen 70-60, 50-40, etc., the number used with these bitumens indicates the range of penetration of the test needle in its test. It is important that there is a direct relationship between the viscosity and the degree of penetration of bitumen, which increases with the increase of the hardness of the soft point, and the degree of its reduction decreases. The test to determine the degree of penetration of bitumen is done to determine their relative hardness and is one of the most widely used tests related to bitumen, and one of the methods of naming types of bitumen is to use their degree of penetration.
Due to the fact that bitumen has a viscoelastic nature, its behavior changes with the degree of urgency and the amount of change per unit of time. In hot weather, bitumen acts like a viscous liquid, and in this case, the deformation is permanent and the grooves are less reversible. . It is formed and in cold weather bitumen acts like an elastic solid material and is deformed when passing vehicles and returns to its original shape during loading, but may become brittle and crack during loading. Typical tests are performed at a temperature of 25 degrees, and this does not indicate the behavior of bitumen at other temperatures. Viscosity test only gives specific information about the viscous behavior of bitumen in a certain range and does not show the behavior of bitumen at higher and lower temperatures.
An important application of the value of the degree of penetration is to find out the area where bitumen is used. In hot areas, bitumen with a higher temperature is used for roads with a higher temperature, and bitumen with a higher penetration degree is used for cold areas. will be It is less exploited. So, as the bitumen becomes harder, its grade decreases, and the softer the bitumen, the higher its grade.
This test is the following ASTM D 5h standard system:
Penetration test definition:
This test is to measure the consistency of bitumen and bituminous materials, which is performed vertically in samples of special conditions based on the length of a standard needle in tenths of millimeters.
Purpose of penetration test:
The purpose of this test is the degree of penetration of bitumen and bituminous materials in solid and semi-solid form. This test is used to measure the consistency, where a higher degree of penetration indicates a lower consistency and a lower degree of penetration indicates consistency.
Conditions for taking the entrance exam:
The standard needle length for this test is 50 mm and for long needles 60 mm.
The specifications of the sample container should be as follows:
For a degree of penetration less than 200, the diameter of the container should be 55 mm and the internal height should be 35 mm.
For the degree of penetration between 250 and 350, the diameter of the container should be 55 to 75 mm and the internal height should be 45 to 70 mm.
For the degree of penetration between 350 and 500, the diameter of the container should be 55 mm and the internal height should be 70 mm.
For this test, the bathroom must have the ability to hold water in the test with an accuracy of one tenth of a degree Celsius.
The weight of the needle assembly with the holder is 100 grams, and the duration of the needle sinking into the sample is 5 seconds.
Penetration test description:
In this test, bitumen or bituminous material is poured into the sample container so that after cooling the surface of the bitumen or bituminous material is completely level with the edge of the container. After pouring the sample into the container, it should be cooled in the environment for 1 to 1.5 hours, and then it should be placed in a water bath at 25 degrees Celsius for 1 to 1.5 hours. After this time, the sample is placed under the measurement along with the container of water containing the sample, and penetration is done as follows:
Places the sample container under the measuring device and allows the tip of the needle to touch the surface of the sample. Press and the needle will go into the sample for 5 places. To perform the penetration test, at least three needles are used in the form of a triangle (so that the distance between the tip of each needle and the inner wall is 1 cm). The results of the three-needle immersion rate test are reported.
