Section 18: Brooming Excess Aggregate
Anchor: #i1007974Introduction
After the aggregate is spread and rolled, there will be some loose aggregate. This excess aggregate should be removed to prevent it from being whipped up by vehicle tires. Loose material may act to dislodge other aggregate under traffic shear forces.
Anchor: #i1007984Timing
The excess aggregate should not be broomed off the roadway as soon as the rolling is finished. The asphalt is still too soft and must be allowed to stiffen or cure before brooming. Otherwise, the broom will strip the aggregate away from the binder. If necessary, light brooming may be performed before opening to traffic to remove excess aggregate that is not embedded in the asphalt. Final brooming should be done as soon as the binder is fully cured: on the same day or the following morning. Best results are obtained by waiting until the following morning (as early as possible). Temperatures are lower during the early hours and the aggregate will be held more firmly in place with only the excess aggregate removed.
Anchor: #i1007997Equipment
The only equipment needed is a rotary broom or a vacuum sweeper for curbed roadways. One or two pickup trucks may accompany the broom, especially if there is a high volume of traffic. One truck may lead and the other follows the sweeper as a warning to traffic. Pickup trucks and sweepers must have appropriate warning devices.
Anchor: #i1008007Procedures
The sweeper should begin at the centerline and sweep the aggregate toward the outside edge of the roadway. It is always best to broom excess aggregate away from traffic. Regardless of how many passes are required, the objective is to broom the excess aggregate off the roadway surface.
Anchor: #i1008017Inspection
Ensure that all excess aggregate is removed from the roadway surface including intersections. Extra brooming may be required at the transverse joints where aggregate tends to overlap. Care should be taken to ensure that large quantities of aggregate are not swept onto adjacent private property. In addition, the operation should be carefully observed to assure that the sweeper is not dislodging aggregate that is embedded in the binder. Also ensure that sweeping is performed safely and with minimum interruption or delay of traffic.