Asphalt, or asphalt cement, is a petroleum product derived from the distillation of crude oil. It is the "bottoms" from the distillation tower, and it is used in many applications. Figure 1 is a schematic of the Moose Jaw refinery, a typical layout of an asphalt refinery.

HMA plants are either batch or drum mixer plants. The purpose of both these plants is to mix the right proportions of asphalt and aggregate to meet desired specifications. Figure 2 shows asphalt cement, aggregate, and the asphalt mixture. The batch plant heats the aggregate and mixes it with the asphalt cement in a pug mill. The drum mixer plant drops aggregate into a sloped drum near the furnace. As it reaches the end of the drum, the asphalt cement is dropped in and turned with the aggregate. The amounts of aggregate and asphalt cement are computer controlled to meet particular specifications. Asphalt is then stored in silos or storage bins.

Figure 2. Aggregate, asphalt cement, and asphalt mixture

Figure 3. Asphalt and Shingle Recycling Plant