TM 5-822-10/AFM 88-6, Chap. 6
density is obtained. Scarifying, rejuvenating, and compacting a surface without the addition of an overlay may cause an
excess of coarse aggregate on the surface. This coarse aggregate makes the scarified material difficult to compact and
results in a surface that tends to ravel. The scarifying, rejuvenating, and compacting procedure should only be used to
improve the surface of mixtures on secondary roads.
g. Overlay approach. An overlay in conjunction with scarifying the pavement is recommended. The overlay may be
added prior to compaction of the scarified material and both layers compacted simultaneously, or the scarified material
may be compacted prior to addition of the overlay. To ensure better bond and better overall density, it is recommended
that the overlay be placed immediately after scarifying the surface and the entire depth of material compacted. Although
this scarification and overlay approach has been used on airfields, generally other alternatives should be selected.
h. Asphalt. The asphalt sampled from the scarified and rejuvenated material should show an improvement in properties
over the existing asphalt properties. Generally, the penetration of the recovered asphalt binder should be 40 to 70. The
amount of binder material added should not cause the voids in the compacted mixture to become overfilled and thus create
an unstable mixture. To determine when a mixture is unstable, samples of the mixture should be obtained and compacted
at 250 degrees F using the standard compaction effort for the job. When the voids of the compacted samples are less than
3 percent, the mixture should be considered unstable, and the amount of rejuvenator should be reduced.
i. Pollution. Pollution caused by smoke from the heating of the asphalt surface may be a problem. But the amount
of smoke can usually be controlled within an acceptable range on most asphalt mixtures. However, heating of pavements
that have numerous sealed cracks will present a problem since the sealer material usually causes an increase in the amount
of smoke during the heating operation.
2-5. Cold milling.
a. Milling process. The milling process, which does not use heat, is used to mill a bituminous or portland cement
concrete pavement to a desired depth. The milling equipment, which can remove up to 4 inches of bituminous mixture
in one pass, uses sensors that follow a stringline grade reference and slope control to directly control the finished grade
(fig 2-5). Since no heat is needed, the pollution problem caused by burning bitumen is eliminated. However, a problem
with dust may occur, but this problem can usually be solved by spraying a small amount of water onto the pavement in
front of the machine. The milling machine can be used during all weather conditions to produce a smoother grade.
Figure 2-5. Pavement cold-milling machine in operation.
2-5
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