The purpose of this test is to determine the linear shrinkage coefficient of asphalt mixture by radiographic method to evaluate its asphalt content and overall performance. During the test, the size and temperature of the specimen should be strictly controlled to ensure the accuracy of the measurement. The equipment should comply with relevant national and industry standards to ensure the reliability of test results. Through the standardized testing process, the construction quality of asphalt mixture is improved, the requirements of engineering application are met, and finally a scientific basis is provided for engineering construction.
Asphalt mixture line shrinkage coefficient test
Purpose and Scope of Application
The purpose of this method is to determine the linear shrinkage coefficient of asphalt mixture, and it is suitable for prismatic specimens cut by wheel rolling plate-shaped specimens. The dimensions of the specimen are 200 mm ± 2.0 mm long, 20 mm ± 1.0 mm wide, 20 mm ± 1.0 mm high. The temperature range and cooling rate of the test are based on local climatic conditions, but the temperature range from +10°C to -30°C and the cooling rate are 5°C/h.
Technical requirements for instruments and materials
Shrink meter – made of stainless steel, with a spherical probe at one end and a dial gauge or displacement gauge at the other, or other instruments for rapid determination of deformation.
High and low temperature circulating constant temperature sink - with automatic temperature control, the temperature control accuracy is ±0.1 °C, the cooling rate is controlled at 1 °C/h, and the internal dimensions are not less than 30cm long, 20cm wide and 15cm deep.
Metal probe – approx. 15mm in length, approx. 5mm in diameter, hemispherical at the end.
Refrigerant – Use a 1:1 solution of methanol in water or antifreeze.
Other tools – thermometer (0.1°C), calipers, balances, iron plates, glass plates, 502 adhesives, etc.
Methods and Steps:
Preparation
1. Make 300mm x 300mm x 50mm plate-shaped specimens according to the relevant regulations, and cut them into 20mm x 20mm x 200mm prismatic specimens, with no less than 3 specimens in a group.
2. Use calipers to measure the size of the specimen, obtain the average of length, width and height to ensure that the cutting size meets the specifications.
3. Determine the density and porosity of asphalt mixture and other physical indicators according to the regulations.
Test procedure
1. Attach metal probes to both ends of the specimen to ensure accurate positioning of the probe and fix it with 502 adhesive.
2. Inject refrigerant into the thermostatic water tank, adjust to the starting temperature of the test (+10°C), and keep it warm for 30 minutes.
3. Quickly take out the specimen, use a dial gauge or displacement gauge to measure the initial length of the specimen, read and record.
4. Place the specimen back in the sink and start cooling down to -30°C at a rate of 5 °C/h and keep it warm for 30 minutes under this condition.
5. Repeat the measurement procedure, record the final length, and determine the shrinkage coefficient according to different temperature intervals.
compute
The average shrinkage strain and average shrinkage coefficient of the cooling interval were calculated using the relevant formulas (T0720-1 and T0720-2). By measuring different temperatures, the shrinkage coefficient change curve is plotted.
report
When the difference between the maximum value and the minimum value does not exceed 20% of the average value, the average value is taken as the test result. The report includes the average linear shrinkage coefficient of the asphalt mixture and the measured values.
Test of bitumen content in asphalt mixture (radiographic method)
Purpose and Scope of Application
This method uses radiographic method to determine the asphalt content in the hot mix asphalt mixture, which is suitable for the mixture mixed with viscous petroleum asphalt, and is mainly used for the detection of asphalt dosage during construction, and quickly evaluates the product quality of the mixing plant.
Technical requirements for instruments and materials
Radiometric asphalt content tester – in compliance with radioactive safety regulations and good operational safety.
Specimen container – a prescribed accessory for the radiometric asphalt content tester.
Asphalt mixture mixer – for sample preparation.
Balances or scales – weighing capacity of 10kg and inductance not more than 5g.
Other tools – shovels, large metal pans, ovens, thermometers, etc.
Methods and Steps:
Preparation
1. Calibrate the parameters of the asphalt content tester. The material is prepared using actual materials, and the temperature is heated to 165°C for 4 hours.
2. Prepare asphalt samples according to the design asphalt dosage and heat to the required mixing temperature.
3. Use an asphalt mixture mixer for mixing, and take the asphalt mixture according to the requirements and load it into the sample container, compacted and put it into the radiographic asphalt content tester.
Test procedure
1. The hot asphalt mixture is individually loaded into the sample container and its mass and temperature are measured.
2. Compacting the mixture to achieve the required volume.
3. Put the sample container into the asphalt content tester in turn, enter the sample number, temperature and calibration parameters for measurement.
report
Record the results of the determination of the asphalt content, evaluate the quality of the asphalt mixture, and ensure compliance with the construction requirements.
summary
The detection of linear shrinkage coefficient and asphalt content of asphalt mixture is an indispensable part of asphalt pavement construction and maintenance. Through standardized test methods and procedures, the accuracy and reliability of test results can be ensured, so as to provide important technical support for road engineering. Both inspection methods can be adapted and optimized for different environmental conditions and equipment availability to suit the actual construction needs.
