The aggregate spreader, sometimes called the “spreader box” is used to distribute aggregate evenly over the film of asphalt sprayed by the asphalt distributor. The specifications require aggregate spreaders to be self-propelled and have a continuous feed feature. The type most commonly seen on a seal coat project is shown in Figure 7‑27.

The spreader receives aggregate from a haul truck that dumps the aggregate into a receiving hopper at the rear of the spreader. A conveyor system transports the aggregate to another bin at the front of the vehicle. Gravity spreads the aggregate evenly across adjustable gates, which allow precise amounts of aggregate to pass through.

The major components of the aggregate spreader are as follows:

The spreader must distribute cover aggregate at a uniform rate over the entire width and length of the area being sealed. Not only must it be uniformly spread, it must also be the correct quantity of aggregate. For a clear understanding of how this is done, each component of the spreader will be described further in this section.

Part of the visual inspection of the aggregate spreader should be directed at the overall condition of the power train, primarily detecting evidence of leaks in the engine and transmissions.

The manufacturer’s name, spreader model number, and serial number should be recorded.