AASHTO T343:12(2020) Standard Method of Test for Density of In-Place Hot Mix Asphalt (HMA) Pavement by Electronic : Surface Contact Devices.
The composition of the HMA mix being tested may significantly affect the measurements. The device should be calibrated to the specific mix design being used in the field.
4.2. This test method may exhibit spatial bias. Oversize aggregate particles in the area of the sensor path may cause variations in density readings. An average of at least four measurements at each test location is recommended.
4.3. The surtce texture of the material being tested may cause lower than actual density readings.
4.4. Electromagnetic force fields, such as those caused by overhead high-tension power lines or large metal objects near the device, may interfere with the device reading.
The device shall meet requirements outlined below:
5.2. The device shall be housed in an enclosure of heavy-duty construction, and designed for taking in situ density measurements of HMA pavements.
5.3. The device shall function at the temperature and moisture levels experienced during the placement of HMA pavements.
5.4. The device shall include the internal circuitry suitable for displaying individual measurements to allow operators to record the results.
5.5. The device shall include a continuous measurement mode of operation.
5.6. The device shall employ suitable electronic circuitry to provide power and signal conditioning to the sensor to provide the data acquisition and readout function, and allow calibration of the unit over the expected range of application conditions and materials.
Because surface conditions can have a significant effect on density measurements, a smooth surface with no excess water (roller water is acceptable) is required for proper testing. The optimum condition for general testing would be a dry, smooth surface, with total contact between the bottom surface of the device and the surface being tested.
6.2. Select a flat, relatively smooth test area on the HMA mat. Brush the surface clear of any sand or stones that would prevent contact between the surface and the measuring device.
Calibrate the device for each mixture prior to performing tests on materials that are different from the material types used in establishing the most recent calibration. Calibrate a newly acquired or repaired device.
If available, a standard plate or reference base shall be used to ensure that the device is within the manufacturer’s specifications.AASHTO T343 pdf download.