surface. In these cases, the roller must be turned around
to allow the tiller wheel to compact the material partially
so the drive wheel can then proceed over it.
tandems, static-weight or vibratory, while the hot mat is
still warm enough for removal of roller marks.
Intermediate rolling should closely follow break-
down rolling, while the asphalt mix is still well above
the minimum temperature of 185 degrees at which
densification can be achieved. Pneumatic-tired or
vibratory rollers may be used for intermediate rolling.
Pneumatic-tired rollers have several advantages:
1. They provide a more uniform degree of com-
paction than steel-wheeled rollers.
2. They improve the seal near the surface by
kneading the material closer together.
3. They orient the aggregate particles for greatest
stability, as high ground pressure truck tires do after
using the asphalt surface for some time.
Tire contact pressures should be as high as possible
without causing displacement of the mix that cannot he
remedied in the final rolling.
Pneumatic-tired rolling should be continuous after
breakdown rolling until all of the hot mix has been
thoroughly compacted. At least three coverages should
NOTE: Turning of pneumatic-tired rollers on the
hot mix should not be permitted unless it does not cause
Vibratory rollers (of proper static weight, vibration
frequency, and amplitude) are used to provide required
densities with fewer coverages than static-weight
tandem or pneumatic-tired rollers (or combinations of
Regardless of the type of roller used, the rolling
pattern should be developed in the same manner as for
breakdown rolling. This pattern should be continued
until the desired compaction is obtained.
Finish rolling is done solely for the improvement of
the surface. It should be accomplished with steel-wheel
Many of the safety precautions previously listed for
graders, scrapers, and dozers also apply to roller opera-
tions. Additional safety precautions are as follows:
. Never perform roller operations alone. Always
have a safety person in the area of the rolling operation.
l Only operate the roller at speeds at which the
machine can be kept under control at all times.
. Always wear a scat belt when rolling, as well as
other required personal protective equipment, such as
steel toe safety shoes and hard hats.
l Operate the roller from the sitting position, never
from a standing position.
. Use the safety handrails when mounting or dis-
mounting a roller. Do not grab the transmission control
levers, as this might cause the roller to make a sudden
l If the roller ignition starts in any transmission
position besides neutral, this machine should be
hardcarded and repaired before further usage.
. Use caution and make sure the area is clear of
personnel, tools, and vehicles when performing forward
and reverse rolling operations.
. A roller is easier to overturn than most equip-
ment. Rolling on a side slope should always be done at
right angles or diagonally, rather than parallel to the
s l o p e .
. Steer carefully when rolling a shoulder to avoid
capsizing into the ditch, and never bring a roller near the
edge of a cut.
c Use extreme care when loading steel-wheeled
rollers on tractor-trailers during periods of inclement
weather, The wet deck of the trailer can cause a steel-
wheel roller to slip during loading and unloading