Asphalt compaction is complex: since the material undergoing compaction is temperature-dependent, it is also time-dependent.

Current state DOT compaction specifications generally focus on the following objectives:

• Construction operations: Lift thickness, roller specifications, rolling pattern, temperature range, visual observations, etc. May be based on data collected from test beds.
• Finished properties: Density or voids (based on a nuclear gauge or pavement cores), and strength or stiffness (based on cores or other field tests).

IC Specification Guidelines

IC concepts and capabilities for asphalt materials were developed later than those for soils and aggregates. Asphalt compaction is complex: in addition to requiring a different roller configuration, asphalt is temperature-dependent and the possibility of damaging the material is greater. Developing specifications for asphalt pavement materials involves considering the varied approaches of several roller manufacturers. At the moment, different manufacturers' versions of IC technology vary greatly in availability and sophistication. For example, some IC rollers track only asphalt mat temperatures and the number of roller passes – however, the benefits from just these features alone can significantly improve asphalt compaction.

Specifications for IC of this material type should be flexible enough to utilize the benefits of all available rollers. The capabilities of dual-drum IC rollers are expected to evolve over the next few years, so specifications must be able to evolve as well.

The current US HMA IC specifications are as follows:

• 2012: FHWA - Generic HMA IC Specification
• 2013: AASHTO draft IC specification

For further information, please visit the specifications literature listed in the online intelligent compaction library.