16.2.7 DRUM PLANT
In a drum plant, the aggregates are dried, heated, and mixed with the asphalt binder in the same
drum, which is usually longer than the dryer drum used in a batch plant, and which is generally
of the parallel flow type, in which the aggregates enter the drum in the same side as the burner
flame. The drum has three distinct zones—the drying, heating, and mixing zones. The flame in
the drum is shorter and wider, and the aggregates are kept in flights along the perimeter of the
drum in the first zone, to prevent them from coming in direct contact with the flame. In the second
zone, the flights cascade the aggregates through the center of the drum and through the hot
burner gases, and as a result the aggregates get heated up to a high temperature.