In this study, we explored the capillary method of the kinematic viscosity test of asphalt, which aims to determine the fluidity of different types of asphalt at specific temperatures. Using a Kfin viscometer and a Thermostatic Water Bath, the test process includes sample preparation, cleaning, temperature control, and data logging. The results show that this method can effectively evaluate the physical properties of viscous petroleum asphalt and liquid petroleum asphalt, and provides a reliable basis for the selection of viscous petroleum asphalt and the determination of construction temperature in engineering applications. The test has high repeatability and accuracy, and is suitable for the performance analysis of different asphalt materials.
Purpose and Scope of Application
The main purpose of the asphalt kinematic viscosity test is to determine the flow behavior of different types of bitumen at specific temperatures. This method is suitable for the kinematic viscosity assessment of viscous petroleum asphalt, liquid petroleum bitumen and their post-distillation residues, especially at 135°C (for viscous asphalt) and 60°C (for liquid asphalt) to help determine their suitability and performance during construction.
Technical requirements for instruments and materials
Capillary viscometer
Choosing the right capillary viscometer is the key to a successful experiment. The Cannon-Fenske counter-flow capillary viscometer is recommended, which is characterized by high accuracy and ease of operation. In addition, other types such as Zeitfuchs Cross-Arm and Lantz-Zeitfuchs can also be used for this test. The calibration constants for each viscometer need to be confirmed based on the data provided by the manufacturer.
Thermostatic sink or Oil Bath
The thermostatic equipment shall be equipped with a transparent wall or observation hole to ensure that the volume is not less than 2L, and the distance between the sample and the bath wall and the bath surface shall be at least 20mm. Its temperature control accuracy should reach ±0.1°C, and it is equipped with a heating temperature regulator and an automatic stirrer to ensure uniform heating.
thermometer
The thermometer graduation value is required to be 0.1°C, and the temperature of the liquid during the experiment needs to be accurately monitored to ensure the stability of the experimental environment.
Other instruments and materials
Oven – with automatic temperature control to ensure specimen preheating and drying.
Stopwatch - the index value is 0.1s, the measurement accuracy is high, and the error does not exceed ±0.05%.
Water flow pumps or rubber balls – used to draw and fill specimens.
High flash point mineral oil or silicone oil – used to maintain a constant temperature environment.
Chemically pure trichloroethylene – used to clean viscometers.
Other materials – including lotions, distilled water, etc.
Methods and Steps:
Preparation
Specimen selection
According to the preliminary estimated viscosity, select a capillary viscometer with the appropriate diameter. In general, the specimen should not flow through the capillary for more than 60 seconds, and if it does, a viscometer with a smaller diameter is used.
Washing and drying
Wash the viscometer thoroughly with a solvent such as trichloroethylene to remove the oil. After washing, it is placed in an oven at 105°C±5°C to dry, or blown dry with hot air. Make sure the viscometer is warmed up to the set temperature before the test.
Prepare liquid bitumen
Stir the liquid bitumen well for 30 minutes at room temperature to avoid the introduction of air bubbles. If the viscosity is too high, it should be heated in an oven at 60°C ±3°C for 30 minutes to make it suitable for testing.
thermoregulation
Adjust the temperature of the Thermostatic Water Bath or Oil Bath to the test temperature ±0.1°C to ensure that the temperature is stable.
Test procedure
Fill with specimens
The preheated capillary is turned upside down and the specimen is aspirated using a rubber ball or water flow pump to ensure that the capillary is completely filled. Then clamp the inflatable tube with a clamp and quickly dry the excess specimen on the outside of the capillary to return to its normal position.
Measurement begins
Place the viscometer in a thermostatic sink and secure the L-tube so that it is vertical. Make sure the D-ball is submerged in water or oil at least 20mm below. Loosen the clamp so that the specimen flows halfway to the reticle and quickly clamps and stops the flow.
Measurement records
Hold at a constant temperature for 30 minutes, then relax the clamps to allow the specimen to flow by gravity. Turn on the stopwatch, and when the liquid level of the sample flows through the reticle E to F and F to J, the time taken is recorded separately to an accuracy of 0.1s. If the specimen flow time is less than 60 seconds, it should be replaced with a capillary with a smaller diameter and the above steps should be repeated.
compute
The kinematic viscosity is calculated from the recorded time, and the data is processed using a formula. It is recommended to test the same specimen in parallel with at least two capillaries, taking the average value as the final result.
Allowable error
Viscous asphalt – the permissible error is 3% of the average.
Liquid bitumen – different permissible tolerances are set according to the kinematic viscosity range of 60°C, and the specific ranges and standards are as follows:
Kinematic viscosity < 3000 mm²/s with a permissible error of 1.5%
Kinematic viscosity 3000~6000 mm²/s, allowable error of 2.0%
Kinematic viscosity > 6000 mm²/s with a permissible error of 8.9%
conclusion
Asphalt kinematic viscosity test is an important tool to evaluate the performance of asphalt, and can provide a scientific basis for the use of asphalt in engineering applications through systematic testing process and strict standards. This method not only ensures the accuracy and reliability of the experiment, but also lays a foundation for the selection of asphalt materials and the determination of construction temperature. With effective operation, researchers and engineers can gain insight into the flow of asphalt to optimize application and use scenarios.
summary
The kinematic viscosity test of asphalt can effectively determine the fluidity of asphalt at a specific temperature by capillary method, which has important practical application value. The systematization and accuracy of this method ensure the performance evaluation of viscous petroleum asphalt and liquid petroleum asphalt, and provide a scientific basis for engineering construction and material selection. Through standardized operating procedures and strict quality control, the reliability of the test results is guaranteed, which provides a solid basis for the optimal use of asphalt.
