Bitumen viscosity test and its methods:
The internal stability of liquids that prevents their fluidity and flow is called viscosity.
This viscosity for liquids is measured in terms of poise.
Normally, all bitumens that have the same penetration degree at 25°C may have different hardness at higher temperatures. For this purpose, an experiment should be conducted to determine their differences.
Bitumen viscosity is a quantity that determines the properties of bitumen at high temperatures where most bitumen mixtures are made at these temperatures. This quantity is effective in determining the behavior of bitumen in such a way that the more sensitive the size of bitumen is to heat, the lower its viscosity will be at high temperatures.
It should be noted that the lower the viscosity of the bitumen, the easier it is to manufacture and produce asphalt, and the bitumen is moved from tanks and bitumen mixed with stone materials easily.
Determining bitumen viscosity by Sibolt’s method
Another point that should be noted is that the mental retardation of bitumen has a direct relationship with asphalt endurance along with temperature changes.
That is, if the asphalt is low, the bitumen will turn into a paste in the heat of the summer, causing the asphalt to ripple under the load of traffic, and bitumen will also occur.
Also, if the bitumen viscosity is higher, the asphalt will crack in the winter cold.
There are various methods for testing the viscosity of bitumen and determining the viscosity of bitumen, which can be called the C-Bolt-Forel method, the standard viscometer method (V.T.S., Wood Red viscometer method) and the kinematic method.
The Sibolt-Forel viscometer is used to determine the viscosity of mixed bitumen and is generally similar to the V.T.S viscometer and is considered a modified type of redwood viscometer. Since the diameter of the hole of the Sibolt-Forel viscometer is smaller than the diameter of the hole of the V.T.S viscometer, therefore the test temperature will be higher in this viscometer.
In the Sibolt-Forel Kandrovani device, the time required in seconds for the amount of 60 cubic centimeters of liquid bitumen at a temperature of 135 degrees Celsius to fall from the channel of the Sibolt-Forel device is determined. This test is according to the standard
ASTM D88 is performed.
Redwood viscometer is used to determine and test the viscosity of liquid bitumen. Since the diameter of the hole of this viscometer is small, pure bitumen and even mixed bitumen pass through it slowly and need a long time. of this viscometer in measuring the viscosity of bitumen which is mixed with solvents such as kerosene, diesel and gasoline
Determination of bitumen viscosity by Sibolt method
which are used in the preparation of mixed bitumen. You can find more content to the standards below
Standard Methods, (IP. 70/57)
Standard Methods, (Paragraph 21.11)
In the kinematic method of measuring viscosity, when 50 ml of bitumen tested at a temperature of 40 degrees Celsius passes through the standard tube of the device, we note the time spent passing the bitumen and this time is considered as bitumen viscosity. let’s show
This viscometer, which is known as V.T.S. viscometer, is used to measure the viscosity of mixed bitumen and tar bitumen. This viscometer is similar to the redwood viscometer, in which a certain amount of bitumen passes through a hole with a certain diameter at a certain temperature, and the passing time in seconds is recorded as the viscosity of the bitumen. This method is not included in the ASTM standard, but it is included in the following standards:
Standard Methods, (IP. 72/58)
Standard Methods, (RT. 2/57)
1- Determination of bitumen viscosity by Sibolt method
2 – The goal
The purpose of viscosity test is to determine the flow properties of bitumen at high temperatures and to determine the performance of asphalt.
3- Specifications of the device and its accessories
1. Seabolt device
3. Molten bitumen
4. Special container
4 – Test method
Before starting the experiment, the Sibolt device should be washed and dried with carbon tetrachloride or kerosene solvent. Now we heat the bitumen to a temperature of about 138 degrees Celsius and pass it through a 200 grade sieve to remove its impurities. We turn on the Seabolt machine until the temperature of the oil around the bitumen tank reaches about 135 degrees Celsius. This temperature should be measured with a continuous thermometer. Now we pour the bitumen inside the tank of the machine and pull up the rod on the nozzle and calculate the time during which the glass container under the nozzle is filled with bitumen to the size of 60 cubic centimeters. This time in seconds will be the same amount of bitumen.
Be sure to empty the glass container of bitumen after the test and clean it with a suitable solvent.