High Resistance Polymermodified Binders to Secure ... - Nynas

3.1.1 German Wheel Tracking Test
The German Wheel Tracking test is used to measure in the laboratory the resistance
against deformation and stripping of the binders on compacted asphalt samples.
Asphalt plates can be tested dry or under water with loaded steel or rubber coated
wheels. The test conditions are shown in the documentation (TP A StB).
The test is mainly used for extended qualification tests and as a tool for development
of improved mix formulations or development of improved bituminous binders. Great
experience is based on asphalt binder mix formulations measured normally at 50°C
under water with a steel wheel. A principal drawing of the test arrangement is shown
in figure 2.
loading: 700 N
20.000 wheel passes
test wheel
∅ 20,3 cm / width 4,7 cm
drive wheel
specimen
26 x 32 x 5 cm
Figure 2: Principle of the German Wheel Tracking Test
water bath
In the German Wheel Tracking Tester two asphalt specimen of 260 x 320 x 50 are
tested simultaneously. The steel wheels charge the specimen with a load of 700 N.
The results are indicated as vertical movement of the wheels in dependence of the
number of passes. They are graphically shown as the mean of the two samples.
Normally the results after 20.000 wheel passes are stated. The speed of the test
wheels is 53 min -1 . The test is terminated earlier when a maximum rut depth of 20
mm is reached.
For the compaction of the test plates a Linear Kneading Compactor was used. This
compactor has shown good correlation with field compaction. The calculated amount
of asphalt is weighed and put into a metal mould of 260 x 320 mm. Steel lamellas of
100 x 10 x 260 mm are placed on top of the uncompacted sample in the mould. The
necessary amount of asphalt is calculated on basis of the bulk density of a Marshall
Test Specimen. By help of a hydraulic press a steel wheel is progressively lowered
until the steel lamellas are even with the upper border of the mould.
The table 2 shows the exceptional well results of the wheel-tracking test. The test
was done at 60 °C (because the values for 50 °C were too small) water temperature
and with a steel wheel. Both values for the used asphalt mixture 0/16 S are below 2
mm. The German limit for binder courses is below 3,5 mm. In comparison with the
Nypol 25 HR you can see in table 2 the results of the higher polymermodified binder
that was advertised for the bid from the tender of the Container Terminal Hamburg.
For the mixture of the binder course it is similar the same behaviour. For the stone
mastic asphalt the Nypol 25 HR reach a better result of roughly 30 percentage.