Hot mix asphalt services

Hot mix asphalt (HMA) is a combination of aggregate and asphalt binder mixed at an elevated temperature to form a hard, strong pavement construction material. It can be designed in the laboratory at four levels (50, 75, 100, and 125 gyrations) simulating four different 20-year traffic levels in the field.

The majority of WSDOT highway mixes are designed at the 100-gyration level. While appropriate for WSDOT highways, this system is not likely to be appropriate for facilities with lower traffic volume, such as the majority of city streets and county roads in the State of Washington.

Aggregate and Performance Graded (PC) binder alone will not improve bad roads. To effectively utilize HMA, local agencies need to do four things:

1. Design the correct pavement section for the roadway needs.

• Pavement Management Tools

2. Select the correct gyration level mix during pavement design.

• Calculate equivalent single axle load (ESAL) (Excel Spread Sheet 23KB)
• Select gyration level (PDF 63KB)
• Select binder grade (PDF 43KB)

3. Ask for the correct mix in the contract documents.

• Sample Proposal item (PDF 8KB)

4. Incorporate appropriate specification changes to implement the process you want during construction.

• Local Agency Special Provisions