Asphalt Placement Methods

Delivery

• To prevent marks in the smooth track of the screed, when the dump truck pulls up to the site it should stop before the paver. The screed is a flat tool which spreads the asphalt evenly. If done correctly the paver will continue forward to meet the truck. The paver hopper should be 25 to 75 percent full. Visually this is indicated when the slat conveyors are no longer visible from the bottom of the hopper. The truck bed should be raised next, letting the mix contact the tailgate to minimize segregation. When the mix is emptied, the slat conveyors can be used to pick up excess mix off the road.

After Delivery

• When the asphalt mix is emptied the truck driver should pull away in a manner that keeps the paver most stable. The bottom of the flow gates is the minimum level at which the mix should remain in the hopper. At this point in the placement process the slat conveyors should still not be visible. After one truck delivers asphalt, another will take its place. Once this happens, the parked truck can access its wings. If the mix is cooling it may accumulate in the corners of the hopper. Folding the paver wings can help eliminate this issue.

Truck Exchange

• When trucks exchange the pavers do not operate. However, the level of mix in the hopper becomes a major issue. If the hopper empties, the screed can fall and reduce the thickness of the asphalt mat being laid. This occurs because the amount of mix contacting the screed determines its height and thus mat thickness. If the amount of mix in the hopper is high, the mat will thicken. Other factors affecting the mat include the pace of the paver. To keep the material even against the screed, the flow gates should be adjusted to provide the slat conveyor and auger near constant operation.

Automatic and Manual Pavers

• Whether a paver is automatic or manual affects the parameters of asphalt placement, primarily due to its interaction with the screed. Automatic options include automatic grade, slope and flow control. Unlike manual pavers the angle of the screed self-adjusts in automatic pavers, and thus should not be adjusted via the thickness controls. Maintaining the mix on the screed in automatic pavers requires exacting placement of the automatic flow control devices to prevent over or under flow. In manual pavers the thickness controls should only be used to adjust the thickness of the mat. If this is performed it should be done with paver arm adjustment time kept in mind.