Measurements were carried out with a Dynatest 8081 Heavy Weight Deflectometer (HWD), capable of applying a dynamic load of 240 kN, and measuring the surface deflections at 9 positions. A minimum of three load levels was used for each test location.

The three loads were necessary for several reasons.

• On concrete pavement, regression analysis could be used to determine the degree of voiding.
• On flexible pavement, the engineer can look at the elastic and plastic deformation responses from the pavement.

Additionally the HWD system has an infra red surface temperature probe and an air temperature probe.
This allows monitoring of the temperature throughout the testing period allowing for more accurate analysis. Temperature where also taken from drilled holes at half depth of the asphalt, the temperature information was combined with three day average temperature to determine the mean asphalt temperature with the Bells equation.

The Dynatest FWD/HWD has within its field program QA checks.
The following QA checks are carried on every test.

Deflection Decreases
This function checks that the deflections are decreasing with time, thus ensuring testing has not been undertaken in the wrong place (i.e. a place that could not be used during certain analysis procedures), or there is a fault with the geophone seating or the geophone itself.

Roll Off
Ensures the electrical signal decreases with time. Showing there is no electrical fault in the deflection reading.

Overflow Check
Ensures all deflections are within the limits of the transducers, used for the measurement of the deflection. If the deflection goes out of the defined limits they can not be guaranteed to be accurate to the manufactures specifications, and therefore should not be used in the deflection analysis.

Load and Deflection Consistency Checks
The load and deflections are checked from one drop to the next for a variation, removing the chance of collecting inconsistent or incorrect data. These variation limits are set for the load at 2kPa or 2% and for the deflection 2mm or 2%.

All HWD tests were related to a zero chainages, which are identified in a site drawing. The zero chainages were referenced to physical marker that would not change over the life of the airport. The tests were undertaken along a series of linear offsets running parallel to the centreline of the runway, taxiway or stand. For subsequent measurements to be monitored over time it is necessary to identify homogeneous sections, which may be defined after the analysis has been undertaken, or split/combined from within the AIRPORTS system.