Hot Mix Asphalt Design Tool
See also Glossary of Asphalt Terms
Hot Mix Asphalt (HMA)
Hot Mix Asphalt is defined as a specifically designed mixture of well graded aggregate combined with an asphalt cement binder. The HMA is compacted to a required density to provide for structural stability in road building. Common terms often used for HMA include blacktop and bituminous.
Aggregates include solid rock and sand materials that are mixed with asphalt cement binder to form HMA. Aggregates must be properly selected and graded to maximize the performance of the HMA pavement.
Asphalt Cement Binder
Asphalt Cement Binder is a viscous bituminous liquid that provides the “glue” material that combines with well-graded aggregates to produce an HMA pavement.
Emulsions are a combination of asphalt binder droplets, water, and emulsifying agents. Diluted emulsions are often used as a tack coat between HMA lifts in road construction.
PG Grading is the current asphalt binder grade designation replacing “penetration” and “viscosity” grading. PG is short for Performance Graded and is based on the performance of a bituminous material at specific temperature and aging conditions. PG graded binders are designed to resist pavement rutting, fatigue, and low temperature cracking for the range of temperatures that they are expected to perform under. PG 58 -28 is the most commonly specified PG grade in Minnesota. In this case, the number 58 refers to the average seven-day high pavement temperature (Degrees Celsius, 58° C = 136° F) that the pavement is expected to be subjected to. The number -28 refers to the minimum air temperature (Degrees Celsius, -28° C = -18° F) that the pavement will be required to perform under.
For updated information regarding PG Grading guidelines and specifications, visit Mn/Dot’s current list of technical memorandums.
Additional information for specifying asphalt PG binders is available at the Asphalt Institute’s Technical Focus Area