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The NETC test road
project was completed to determine the effect of tire shreds on frost
penetration and drainage underneath paved roads. The project was carried
out on the University of Maine Witter Farm Road. The test road included a
control area without tire shreds to use as a comparison against sections with
tire shred fill and tire shred/gravel mixtures. Figures 1 and 2 show cross
sections of the test road.
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Figure 1. Longitudinal section along centerline of road (Lawrence, et al.,
1998)
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The graphs in
figure 3 show frost penetration below the different sections of the test road
(shown above in figure 1) and figure 4 shows the maximum depth of frost
penetration at each section. Tire shreds clearly reduce the depth of frost
penetration, although mixtures of tire shreds and gravel don't work as well as
tire shreds alone.
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Figure 3. Frost penetration versus date for NETC test road (Lawrence, et
al., 1998)
Figure 4. Maximum depth of frost penetration for winter of 1996/7 in the
NETC test road. (Lawrence, et al., 1998)
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Figure 5 shows
average frost heave for individual wheel paths on each section of the test
road. Frost heave was generally greater for the outer wheel paths,
possibly because there was greater access to water and frost penetration
occurred beyond the edge of the tire shreds. Frost heave for the inner
wheel paths in the sections with tire shreds was very small compared to the
frost heave that occurred in the control and tire shred/gravel-mix sections.
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Figure 5. Average frost heave in individual wheel paths in the NETC test
road
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The tire shreds' back calculated thermal
conductivity ranged from 0.16 to 0.18 W/m-°C(0.9-0.10
Btu/hr-ft-°F).
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