The purpose of this study was to evaluate the mechanical properties of asphalt mixture and its low-temperature crack resistance by splitting test. In the experiment, the tensile strength and stiffness modulus of the cylindrical specimens were tested under different loading rates and temperature conditions. Use Marshall's standard testing machine and displacement sensor, combined with a thermostatic bath, to control environmental variables to ensure the accuracy and reliability of test data. The results show that different temperatures and loading rates have significant effects on the properties of the mixture, which provides an experimental basis for improving the low-temperature properties of asphalt materials.
Purpose and Scope of Application
The asphalt mixture splitting test is used to evaluate the mechanical properties of the asphalt mixture at a specified temperature and loading rate, especially its low temperature crack resistance. This test is suitable for the design of asphalt pavement structure, the selection of mechanical parameters of asphalt mixture, and the evaluation of the crack resistance of asphalt mixture. The test temperature should be selected according to the local climatic conditions, and it is recommended to perform it at 15°C±0.5°C with a loading rate of 50 mm/min. When evaluating the crack resistance at low temperature, the test temperature should be -10°C±0.5°C, and the loading rate should be 1 mm/min.
Specimen requirements
Specimen shape and size
Diameter - When the nominal maximum particle size of the aggregate is less than or equal to 26.5 mm, a cylindrical specimen with a diameter of 101.6 mm±0.25 mm and a height of 63.5 mm ± 1.3 mm is used.
Drill specimens – cylindrical specimens with diameters of 100 mm±2 mm or 150 mm±2.5 mm and heights of 40 mm±5 mm can be drilled in the field.
Materials & Instruments
Testing machine – with the ability to maintain the specified loading rate and test temperature, it is recommended to use a 40 kN or 60 kN sensor with a maximum measured load of no more than 80% of the measuring range and not less than 20%.
Displacement sensor - LVDT or electrical dial gauge should be used, and non-contact displacement sensor should be used for horizontal deformation.
Data acquisition system – should be able to automatically collect sensor signals and store or plot load and deformation curves.
Constant temperature sink - used to keep the specimen warm, the temperature control accuracy should be ±0.5°C.
Test procedure
Preparation
1. Prepare the cylindrical specimen according to the prescribed method.
2. Accurately determine the diameter and height of the specimen, and mark the crosshairs on both sides of the specimen.
3. Measure the density, porosity and other physical indexes of the specimen.
4. Immerse the specimen in a constant temperature water tank for at least 1.5 hours until the internal temperature reaches the test requirements.
5. Ensure that the ambient temperature of the testing machine meets the requirements.
The process of the test
1. Place the insulated specimen in the testing machine fixture to ensure that it is aligned and centered.
2. Install the deformation measurement device and connect the recorder with the load and displacement sensor.
3. Start the testing machine and apply a load to the specimen at the specified loading rate until the specimen is destroyed.
4. Record load and deformation data and draw load-deformation curves.
Calculation method:
1. Determine the maximum load and maximum deformation according to the load-deformation curve, and calculate the parameters such as splitting tensile strength, Poisson's ratio, failure tensile strain and stiffness modulus.
2. In the straight segment of the small deformation zone, calculate the stiffness modulus of the elastic phase.
Report on the results
The report should include information such as the size of the specimen, the molding method, the test temperature, the loading rate, etc. If a measured value deviates from the mean by k times the standard deviation, the value should be discarded and the average value of the remaining measured values should be used as the test result.
summary
The asphalt mixture splitting test is an important testing method to evaluate the mechanical properties of asphalt mixtures, especially the crack resistance under low temperature conditions. The test provides the necessary data support for the design of asphalt pavement and ensures the performance stability of asphalt mixture in different environments. The accuracy and reliability of the test results can be improved through standardized test procedures and detailed calculation methods.