1. This method is suitable for measuring the rutting resistance of asphalt mixture at high temperature, and is used for the high temperature stability test of asphalt mixture ratio design.
2. The test temperature and wheel pressure of rutting test can be selected according to relevant regulations and needs. Unless otherwise specified, the test temperature is 60℃ and the wheel pressure is 0.7MPa. If necessary, 45℃ can be used in cold areas and 70℃ can be used in high temperature conditions, but it should be noted in the report. In principle, the time for calculating dynamic stability is between 45 minutes and 60 minutes after the start of the test.
3. This method is suitable for the plate-shaped specimen rolled by the wheel rolling forming machine with a length of 300mm, a width of 300mm and a thickness of 50mm, and also suitable for cutting and making the plate-shaped specimen with a length of 300mm, a width of 150mm and a thickness of 50mm on site. According to requirements, the thickness of the sample can also be 40mm or other dimensions.
2. Instruments and equipment
1. Rut tester: It mainly consists of the following parts:
(1) sample table: a test mold that can firmly install samples with two widths (300mm and 150mm) of the specified size.
(2) Test wheel: a solid tire made of rubber, with an outer diameter of 200mm, a wheel width of 50mm, a rubber layer thickness of 15 mm, a rubber hardness (international standard hardness) of 20℃ 84 4 and 60℃ 78 2, a walking distance of the test wheel of 230mm 10mm and a rolling speed of 42 times. It is allowed to use crank connecting rod to drive the test bench (the test wheel does not move) or chain to drive the test wheel (the test bench does not move).
Note: the hardness of tire rubber should be checked, and those that do not meet the requirements should be replaced in time.
(3) Loading device: At 60℃, the contact pressure between the test wheel and the specimen is 0.7 MPa±0.05 MPa, and the total load applied is about 75kg, which can be adjusted as required.
(4) Mould test: it is made of steel plate and consists of bottom plate and side plate. The internal dimensions of the trial die are 300mm long, 300mm wide and 50mm thick (made in the laboratory), and the 150mm wide specimen can also be fixed on site.
(5) Deformation measuring device: a device that automatically detects rutting deformation and records curves, usually using LVDT, electric dial indicator or non-contact displacement meter.
(6) Temperature detection device: a temperature sensor and thermometer that automatically detect and record the temperature of the sample surface and the constant temperature room, with an accuracy of 0.5℃.
2. Thermobox: The rutting tester must be placed in the thermostat, equipped with heater, air circulation device and automatic temperature control equipment, which can keep the temperature of the thermostat at 60℃ 65438 0℃ (the internal temperature of the specimen is 60℃ 0.5℃), or at other required temperatures as required. Used for insulating specimens and tests. The temperature shall be recorded automatically and continuously.
3. Platform scale: weight 15kg, sensitivity not exceeding 5g.
Three test preparations
1. Measurement of the ground pressure of the test wheel: The measurement is carried out at 60℃. Put a 50-mm-thick steel plate on the test bench, with a millimeter-square paper on it and a new copy paper on it. After the specified load of 700N, the ground contact pressure of the test wheel can be obtained on square paper. When the pressure does not meet 0.7 MPa±0.05 MPa, the load should be adjusted appropriately.
2. The rut test block is made by wheel rolling. In the laboratory or the construction site, rutting specimens are prepared, the standard size of which is 300 mm× 300 mm× 50 mm, and the specimens of 300mm× 150mm×50mm can also be cut from the pavement. When the sample of mixed asphalt mixture is directly taken out from the mixing station to make a test piece, so as to check the production mix design or production quality of the mixture, the mixture must be put into a heat preservation barrel and quickly sent to the laboratory to make a test piece before the temperature drops to the molding temperature. If the temperature is slightly insufficient, it can be put in the oven for a short time (no more than 30min) before use. You can also directly use a manual roller or a roller to form a test piece on the spot, but you must not let the mixture cool and then heat and shape it to make a test piece. The test results of remolded parts are for reference only and shall not be used to evaluate whether the mix design inspection is qualified for use.
3. When necessary, demould the sample, and determine the physical indexes such as density and porosity according to the method specified in this regulation. If it is soaked in water, use an electric fan to dry it, and then put it back into the original test mold.
4. After the sample is formed, it should be placed at room temperature with the test mold for not less than 12h. For polymer modified asphalt mixture, it is advisable to stand still for 48 hours, so that the polymer modified asphalt can be fully solidified before rutting test can be carried out, but indoors
Warm storage time should not exceed one week.
Note: In order to make the specimen in close contact with the test mold, remember that the directional positions of the four sides remain unchanged.
Four test steps
1. Put the sample together with the test mold into a constant temperature room with the test temperature of 60℃ 65438 0℃, and keep the temperature for not less than 5h and 24h. Stick a thermoelectric angle thermometer on the part where the test wheel of the specimen does not walk (or bury the thermoelectric angle wire in a corner of the specimen in advance when making the specimen), and control the temperature of the specimen to be stable at 60℃ 0.5℃.
2. Move the test piece and the test die together to the test bench of the wheel testing machine. The test wheel is located in the center of the specimen, and its walking direction must be consistent with the rolling or driving direction of the specimen. Start the automatic rutting deformation recorder, and then start the testing machine to make the test wheel walk back and forth about 1h, or until the large deformation of zui reaches 25mm. During the test, the recorder automatically records the deformation curve and temperature of the sample.
Note: For the specimen with a width of 300mm and little deformation during the test, it is also possible to conduct two tests at the position of 1/3 on both sides of the specimen and take the average value.
Five kinds of result arrangement
1. Calculation
(1) read the rutting deformation d 1 and d 2 of 45min(t 1) and 6Qmin (t 2), and the accuracy is 0.01mm. When the deformation is too large, when the deformation reaches 25mm before 60min, the time (d 2) to reach 25mm is t 2, the first 15min is t 1, and the deformation at this time is d 1.
(2) The dynamic stability of asphalt mixture specimen is calculated according to the formula.
Xi Anyaxing Construction Instrument Co., Ltd.
Where: DS-dynamic stability of asphalt mixture, times/mm;
D1-time t 1 corresponding deformation, mm;
D 2- 1 deformation corresponding to time t 2, mm;
C 1- 1 Type correction coefficient of testing machine, the variable-speed walking mode of crank-connecting rod driving sample is 1.0, and the constant-speed mode of chain driving test wheel is1.5;
The coefficient of C 2- 1 specimen prepared in the laboratory is 1.0, and the coefficient of1300mm specimen cut from pavement is 0.8.
N- 1 1 The reciprocating rolling speed of the test wheel is usually 42 times/minute.
2. Report
(1) For the same asphalt mixture or the same road section, at least three specimens shall be tested in parallel. When the coefficient of variation of the dynamic stability of the three specimens is less than 20%, the average value is taken as the test result. When the coefficient of variation is greater than 20%, the reasons should be analyzed and supplementary tests should be carried out. If the calculated dynamic stability value is greater than 6000 times /mm, record it as: > 6000 times/mm.
(2) The test report shall explain the test temperature, the grounding pressure of the test wheel, the density of the specimen, the void ratio and the method of making the specimen, etc. The allowable difference of coefficient of variation of dynamic stability in repeatability test is 20%.