The rutting test of asphalt mixtures is mainly used to evaluate the rutting resistance of materials at high temperatures. In this test, the deformation and dynamic stability of the mixture are measured by dynamically loading the mixture at a specific temperature and wheel pressure. The test is required to be carried out in strict accordance with the standard, including the size of the specimen, the manufacturing method and the test steps to ensure the accuracy and reliability of the results, and provide an important reference for the construction quality of the asphalt pavement.
Purpose and Scope of Application
The main purpose of the rutting test of asphalt mixture is to evaluate the rutting resistance of asphalt mixture under high temperature conditions, and to provide a high-temperature stability test basis for the mix ratio design of asphalt mixture. At the same time, this test is also suitable for the high-temperature stability check of asphalt mixtures in the field.
The standard temperature of the test was 60°C and the wheel pressure was 0.7 MPa. In certain situations, such as 45°C in cold climates, 70°C can be used in high temperatures. For heavy-duty traffic, the wheel pressure can be appropriately increased to 1.0 MPa, and the specific situation should be detailed in the test report.
Instrument and material technical requirements
Test equipment
Rutting testing machine is mainly composed of a test piece table, a test wheel, a loading device, a mold test and a deformation measurement device.
Specimen table – different sizes (300mm and 150mm) can be installed.
Test wheel - made of rubber, outer diameter 200mm, width 50mm, rubber hardness needs to be checked regularly.
Loading device – ensure that the contact pressure between the test wheel and the test piece is 0.7 MPa.
Mold trial - made of steel plate, the inner size should be 300mm x 300mm x 50~100mm.
Deformation measurement device - using displacement sensor (LVDT) or non-contact displacement meter, the measurement range is 0~130mm, and the accuracy is ±0.01mm.
Constant temperature room
The constant temperature chamber needs to provide a stable environment to maintain a temperature of 60°C ±1°C and be able to support the simultaneous testing of at least three specimens.
Other equipment
The scale needs to have the capacity to weigh 15kg and the inductance is not more than 5g.
Methods and Steps:
Preparation
1. Determination of grounding pressure of test wheels - determine the grounding pressure by static pressure test.
2. Specimen forming - the rutting test block is made according to the standard method, and it needs to be quickly formed under the condition of suitable temperature.
3. Specimen Placement - The formed specimen should be placed at room temperature for at least 12 hours, and the polymer modified asphalt mixture should be placed for 48 hours to ensure full curing.
Test procedure
1. Preheating of the specimen - preheat the specimen in a constant temperature chamber for 5~12 hours to ensure that the temperature is stable.
2. Test – Put the specimen into the rutting tester, start the automatic recorder, and the test lasts for 1 hour, or until the deformation reaches 25mm.
3. Data recording - automatically record the deformation curve and specimen temperature.
Calculations & Results
The calculation of the dynamic stability is based on the deformation data measured at 45 and 60 minutes. When the deformation of the specimen exceeds 25mm, the deformation at this time point is recorded. The dynamic stability is calculated according to the formula, and the average value is usually obtained among three parallel specimens, and if the coefficient of variation is greater than 20%, the cause analysis and additional test are required.
conclusion
The rutting test of asphalt mixture is an important index to evaluate the ability of asphalt pavement to resist rutting deformation in a high temperature environment. The test can not only reflect the performance of asphalt mixture, but also provide a scientific basis for practical engineering. This detection method is widely used in various countries, which provides a standardized detection method for the design and application of asphalt mixture.