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3. Laboratory Test Methods and
Results
3.4 Wheel tracking
test
Wheel tracking test is a lab simulation test to measure the
property change of pavements under hot temperature and vehicle loads. It is
designed for a speed experiment to be able to measure the depth of wheel digging
by repetitive driving conditions. Thus, it can evaluate the dynamic stability of
hot asphalt mixture. Wheel tracking test result is then displayed on the depth
change and time (or number of loading) relation curve. From the curve, the rate
of depth change per time is shown to be linear between 45 and 60 minutes of
experiment. The rate of change during this 15 minute simulation interval is then
termed to be RD (Rate of Deformation, mm/min). In addition, number of vehicle
loading on the track to lower the depth of the pavement by 1 mm is termed to be
DS(Dynamic Stability, number of loading per minute).
Equations 1 and 2 are
used to obtain the rate of deformation and dynamic stability.
Eq. (1)
Eq. (2)
Here, RD(mm/min) ; Rate of Deformation = the rate of
lowering of the pavement depth per minute during 15 minute interval of between
45 and 60 minutes after start of the test.
DS(numbers/mm) ; Dynamic Stability
= the number of vehicles loading per unit depth change (mm) during 15 minute
interval of between 45 and 60 minutes after the start of the test.
d60(mm) =
rate of change at 60 minutes
d45(mm) = rate of change at 45 minutes.
This study employed wheel tracking test for the comparison test of
resistibility to property change as indicated by the rate of deformation and
dynamic stability by varying the amount of DAMA added to each HMA. The test
results are summarized and depicted in table 10 and figures 15 and 16. Figure 17
shows increased dynamic stability with respect to the increased amount of DAMA.
Figures 18 and 19 depicts the cross-sectional view of the experimental specimen
after the wheel tracking.
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