We know that the TERRATEST 5000 BLU is the Light Weight Deflectometer for dynamic plate load test to check compaction quality in earthworks and road constructions.
I am interested in is it possible to assess the strength of asphalt concrete pavements on highways and urban streets using the TERRATEST 5000 BLU (by definition of elastic deflection)?
Рrobably not! TERRATEST 5000 BLU is designed for testing natural soils and its principle of operation will not allow testing asphalt concrete. To measure the density of asphalt concrete, specialized devices are used, for example, Troxler Model 2701-B PaveTracker Plus - an electronic device equipped with an electromagnetic sensor. It does a good job of assessing the degree of compaction of asphalt to identify areas of segregation, under-compaction, and other irregularities in the asphalt pavement.
Dear Dr. Andrii Velychkovych , Thanks for your helpful response!
But I am interested in what devices are used to measure the strength of asphalt concrete (by definition of elastic deflection, you know), not the density. If you know some, could you share with your experience, please?
Non-destructive testing of the strength or elastic properties of asphalt concrete is usually carried out indirectly. There are different methods with different probabilities of accuracy. For example, a density meter determines density and uses empirical formulas to correlate density values - and strength limits; use the ultrasonic method to determine the mechanical properties of asphalt concrete (non-destructive assessment of the strength of asphalt concrete, see here https://scialert.net/fulltext/?doi=jas.2007.3870.3879).
Of course, the most accurate method will be the direct method: you need to cut samples of asphalt concrete and test them in the laboratory :-)
ps.:If it is possible to obtain at least a few real samples, then according to the obtained laboratory data, it is possible to verify the readings of the ultrasonic apparatus for further non-destructive testing.
the strength of asphalt pavements can be determined using these devices
https://www.sciencedirect.com/topics/engineering/falling-weight-deflectometer
This is from terra test 5000 blu user maual:
4.5 CalibrationBefore delivery 'TERRATEST 4000 USB' and 'TERRATEST 5000 BLU' are calibrated according to German'Technical Test Code for Soil and Rock Mechanics in Road Constructions TP BF-StB Part B 8.3'. Duringcalibration all components of the device, such as the load plate with integrated sensor, the loadingdevice and the electronic testing computer, are attuned specifically to one another. After successfulcalibration, respective calibration tags with the expiry date of the calibration are affixed to the load plate,the loading device, and the testing computer. These calibration marks also contain the name of thecalibration institute and the serial number. Each device is provided with a calibration certificate whichmeets the requirements of the German standard TP BF-StB Part B 8.3. A precise test result can only beguaranteed if the device is used as a single unit with all its corresponding parts. Identification plates withthe same four-digit serial number are located on the load plate, the drop weight and the testing computerfor this purpose. This serial number is also recorded on the calibration certificate. On the identificationplate of the drop weight the date of the last calibration and the respective drop height of the weight in cmare also noted.According to German standard TP BF-StB Part B 8.3 the device must be calibrated at least once a year at acalibration institute accredited by the German Federal Research Institute (Bundesanstalt für Straßenwesen).Test results of a device that has not been calibrated, or of a device with an expired calibration date, mustnot be used for evaluating the bearing capacity of soil and rock. Abide by the mandatory calibrationintervals and ensure that the device is re-calibrated in due time.4.6 12 Rules for Proper Use1. Always perform a correlation measurement with the static plate load test. For every static plate loadtest at least three dynamic tests must be performed.2. The section examined by the device reaches down to a maximum of 40 cm in depth, depending onbackfill materials and subsoil.3. Remove any loose material from the test area; create a smooth and level surface on which to place theload plate. Ensure full and even contact between the load plate and the ground. In the case of soilirregularities, spread a thin layer of sand on the surface and reduce the thickness of the layer by movingthe plate back and forth.4. Keep the guide rod vertical and make sure that the plate does not move horizontally during the impact.5. ATTENTION: The transportation lock must be unlocked before each drop. Catch the weight on the sideopposite the lock. No warranty for damages caused by improper use.6. The decline of the test area must not be greater than 6°.7. Pull on the plugs only, never on the measuring cable!8. Never change the position of the release handle!9. Before each test, make sure that the bottom side of the plate is clean and remove any material stuck to it.10. The grain size of the material to be tested may be a maximum of 63 mm.11. If the three settlement curves vary widely, re-compaction has occurred caused by the test.12. Make sure that latching the drop weight into the release mechanism does not trigger an accidentalreading of the testing computer.
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