HMA production is the first step in construction. The basic purpose of an HMA plant is to properly proportion, blend, and heat aggregate and asphalt to produce an HMA that meets the requirements of the job mix formula (JMF) (Roberts et al., 1996). There are two basic types of HMA plants commonly in use today: the batch plant, and the drum mix plant. Batch plants produce HMA in individual batches while drum plants produce HMA in a continuous operation. Each type of plant can produce the same types of HMA and neither type of plant should impart any significant plant-specific HMA characteristics. The choice of a batch or drum mix plant depends upon business factors such as purchase price, operating costs, production requirements and the need for flexibility in local markets; both can produce quality HMA. This section gives a brief overview of batch and drum mix plants. More detailed information on plant operations can be found in:
- Transportation Research Board (TRB). (2000). Hot-Mix Asphalt Paving Handbook 2000. Transportation Research Board, National Research Council. Washington, D.C.
- Roberts, F.L., Kandhal, P.S., Brown, E.R., Lee, D.Y., and Kennedy, T.W. (1996). Hot Mix Asphalt Materials, Mixture Design, and Construction. National Asphalt Pavement Association Research and Education Foundation. Lanham, MD.