HMA Mixes

Hot mix asphalt (HMA) is high-quality, thoroughly controlled, engineered material. In general, there are two basic ingredients to HMA, aggregates and liquid asphalt.

Aggregates can come in the form of stone, gravel and sand. Which aggregates are used in a given mixture of HMA depends largely what is available locally. It can also be affected by the specifications for the HMA. Generally, aggregates represent about 95% of the total weight of HMA. Aggregates come from either a pit or quarry. A pit is defined as an open excavation where unconsolidated materials are removed for construction, industrial or manufacturing purposes. A quarry is defined as an open excavation where consolidated materials are removed for construction, industrial or manufacturing purposes. In general, quarries require controlled blasting of the consolidate materials.

The remaining 5% is liquid asphalt which is also referred to as asphalt cement or asphalt. Liquid asphalt is a derivative of the crude oil refining process. It is the binder or "glue" in the HMA. Liquid asphalt is one of the heaviest, most viscous parts of the petroleum. This is why it is ideal for "holding" the aggregates together. The two ingredients are mixed together at a plant to make hot mix asphalt.

Source: Wisconsin Asphalt Pavement Association