TM 5-822-5/AFM 88-7, Chap. 1
14-11. Overlay Design Example.
Design an overlay for an existing road having a
plain concrete thickness of 6 inches, a flexural
strength of 650 psi, a subgrade k value of 100 pci,
ho = 4.4 inches (use minimum thickness of 6 inches)
and a design index of 8. The concrete overlay will
also have a flexural strength of 650 psi. The factor
Unbonded Overlay
for projecting cracking in a flexible overlay is 0.975
from figure 14-1. The existing pavement is in good
condition with little or no structural cracking. The
condition factor C is therefore equal to 1.0 for
concrete and flexible overlay. From figure 12-1, hd
and he are 8.6 inches.
Overlay thickness
requirements for the various types of overlays are as
follows:
ho = 6.16 inches (round to 6.5 inches)
Bonded Overlay
ho = hd - hg
Flexible Overlay
ho = 8.6 - 6.0
ho = 2.6 inches (round to 3.0 inches)
to =3.0((Fhd - Chg)
to = 3.0(0.975 8.6 - 1.0 6)
Partially Bonded Overlay
to = 7.2 inches (round to 7.5 inches)
14-7
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