Intermediate Rolling

Intermediate rolling should closely follow breakdown 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 compaction 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 be made.

NOTE: Turning of pneumatic-tired rollers on the hot mix should not be permitted unless it does not cause undue displacement.

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 the two).

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

Finish rolling is done solely for the improvement of the surface. It should be accomplished with steel-wheel tandems, static-weight or vibratory, while the hot mat is still warm enough for removal of roller marks.

ROLLER SAFETY

Many of the safety precautions previously listed for graders, scrapers, and dozers also apply to roller operations. 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 dismounting a roller. Do not grab the transmission control levers, as this might cause the roller to make a sudden movement.

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 equipment. Rolling on a side slope should always be done at right angles or diagonally, rather than parallel to the slope.

. 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 steelwheel roller to slip during loading and unloading operations.