Asphalt is an important material for paving roads, and its performance directly affects the durability and service life of roads. Over time, asphalt deteriorates under high temperatures and oxygen environments, resulting in a decrease in its performance. Therefore, it is particularly important to develop an effective detection method to evaluate the aging resistance of asphalt. This article will introduce in detail the purpose, scope of application, technical requirements of instruments and materials, and specific experimental procedures of accelerated asphalt aging test of pressure aging vessel (PAV).
Purpose and Scope of Application
objective
The accelerated asphalt aging test of pressure aging vessel is designed to simulate the oxidative aging of asphalt in the process of road use, and to evaluate the resistance to chemical aging of different asphalt under specific temperature and pressure conditions by accelerating the aging of asphalt in a pressure vessel through high temperature and compressed air.
Scope of application
This method is suitable for asphalt residues obtained by the Rotary Film Oven Test (RTFOT). It should be noted that this method is mainly used to evaluate the aging ability of asphalt under laboratory conditions, and cannot fully represent the aging effect of mixture factors or asphalt under actual use conditions.
Instrument and material technical requirements
instrument
Pressure Aging Tester (PAV)
It is mainly composed of pressure vessels, pressure control equipment, temperature control equipment, pressure and temperature measurement equipment, film oven sample trays, etc.
Technical requirements
Pressure vessel – pressure range of 2.1MPa±0.1MPa, capable of accommodating up to 10 film oven sample trays.
Pressure control equipment
Pressure reducing valve – prevents pressure from exceeding 2.5MPa.
Pressure regulator – controls pressure at 2.1MPa ± 0.1MPa.
Pressure Relief Valve - Slowly reduce the pressure to atmospheric pressure within 8~15 minutes after the end of the test.
Temperature control equipment - can control the internal temperature at 90~110°C, and the error is ±0.5°C.
Recording equipment - temperature recording is accurate to 0.1°C, pressure measurement is accurate to ±0.02MPa.
Sample tray - stainless steel tray, in line with the standard of thin film heating test.
Balance - inductance is not more than 0.18g.
Compressed air cylinders
material
Bitumen sample – residue from a rotating film oven test (RTFOT).
Methods and Steps:
Preparation
1. Prepare asphalt samples according to the T0602 protocol and obtain residues by RTFOT test.
2. Place the standard film oven test sample tray of known quality on the balance, and add 50g±0.58g of asphalt to the tray to ensure that the film thickness is about 3.2mm. If the residue cools, it should be heated to a flowing state before filling.
Test procedure
Put the sample tray into the pressure vessel, select the appropriate aging temperature, and turn on the heater to preheat the pressure vessel to the set temperature. When the temperature reaches the aging temperature, quickly open the pressure vessel, put in the prepared sample tray, and then close the pressure vessel.
When the internal temperature of the pressure vessel is lower than the target temperature by 2 °C, air is supplied to the vessel, and the air pressure is kept at 2.1MPa±0.1MPa, and the timing is 20 hours ± 10 minutes.
After 20 hours, the pressure reducing valve is opened, and the pressure is slowly reduced to the same as the external pressure, which takes 8~15 minutes.
During the aging process, if the temperature fluctuation exceeds ±0.5°C or the pressure exceeds the specified range, the test sample shall be discarded.
The pressure vessel is opened, the specimen is removed, the residue is poured into the vessel, heat treated and stirred to remove air bubbles, and subsequently the performance determination is performed. If not tested immediately, store with a lid at room temperature and set aside for later use.
Reporting requirements
At the end of the trial, the report should include:
Sample number.
Aging temperature (accurate to 0.5°C).
The highest and lowest aging temperatures recorded (accurate to 0.1°C).
Total aging time (to be accurate to 1 minute).
conclusion
The accelerated aging test of pressure aging vessel is an effective experimental method to evaluate the anti-aging ability of asphalt, which provides a scientific basis for the performance evaluation of asphalt materials by simulating the aging process of asphalt in high temperature and oxygen environment. The rational use of this method can help improve the selection and application of asphalt materials, and improve the service performance and life of roads.
