> Part of the training was on the retro- calculation which makes it possible to convert the measured deflections into elastic modulus for each of the layers composing the roadway.
The data necessary to perform a retro- calculation are:
> deflections and loads of each test FWD / HWD,
> pavement thicknesses, (from core samples and / or GPR data),
> asphalt temperatures.
It is an iterative process performed by specific software. For example, at São Luis airport in Brazil, a retro-calculation was performed from the data:
> of deflections,
> the types and thicknesses of materials determined from geotechnical surveys,
> the temperature of the asphalt at the time of the tests.
The modulus of asphalt changes with the temperature. It is recalculated for a temperature of 25 °. This retro-calculation made it possible to obtain the modulus of the different layers composing the roadway, (chart attached).
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