Principles of Operation for Zorn AT 3000 GPS Asphalt Stiffness Test
The AT 3000 GPS Asphalt Stiffness Test shows the increasing elasticity or deformation modulus in MN/m2 by measuring the deflection of asphalt layers. This helps to safely evaluate bearing capacity of newly placed asphalt layers based on their elastic behaviour.
The AT 3000 GPS Asphalt Stiffness Test works with five drops of a 10 Kg drop weight on a 30 or 50mm diameter stamp with a high‐end acceleration sensor. The deflection of every single drop is recorded and is shown on a printout. The difference in deflection from one drop to the next shows the stiffness of the asphalt layer. Since temperature has a very important influence on asphalt, the Zorn AT 3000 GPS Asphalt Tester has a temperature gauge with an infra-red sensor near the test point. The Excel based software allows linear or exponential approximation and calculates the deformation modulus (EHd) in Mpa or MN/m at the standard temperature of 20C. The deformation modulus (EHd) value is adjusted by temperature.
For decision making and reporting, on‐site printouts or data transmission to PC via SD‐Card are easy to do.
EHd Deformation Modulus calculation
EHd(a) = f * (1 – v2) * sigma * r / s = 1.055 / s
- f=2 shape factor
- v=0.25 Poisson’s ratio (for bound material)
- sigma=93.768N/mm2 loading pressure under the pin
- r=6mm (half diameter of the pin)
In Europe, asphalt thickness ranges from 10cm for normal roads to 16cm for highways.