WHAT IS HOT MIX ASPHALT?

Aggregates and liquid asphalt are the two main ingredients that make up hot mix asphalt.

• Aggregates, which represent about 95 percent of the total weight of the asphalt, are typically stone, gravel and sand. The aggregates used in a given mixture of asphalt depend largely on what is available locally. The pavement design specifications also affect the selection of aggregate type and size.

Aggregates come from either a pit or quarry. Both are open excavations where materials are removed for construction purposes. In a pit, the materials are unconsolidated (or loose), whereas in a quarry, the materials are consolidated, and controlled blasting of these materials is usually required.

• 
  A liquid asphalt tank

  Liquid asphalt represents the remaining 5 percent of the pavement. It is the binder or “glue” in the HMA, and it is also referred to as asphalt cement or simply “asphalt.” Liquid asphalt is a derivative of the crude oil refining process and is one of the heaviest and most viscous parts of the petroleum. These properties make it ideal for holding the aggregates together.

Production

Hot mix asphalt is produced at the plant by drying and heating the aggregates and then mixing and coating them with warmed liquid asphalt. It may sound simple, but this is a very intricate process utilizing state-of-the-art equipment to ensure the highest quality asphalt.

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