Soils IC Specifications

Current US state DOT compaction specifications

Current state DOT compaction specifications often follow one or more of the following approaches:

  • Ordinary Compaction: A specified roller makes a specified number of passes, or makes continuous passes until no further compaction can be observed.
  • Stiffness Control: Each lift is compacted to reach a target stiffness value, which is often measured with a Dynamic Cone Penetrometer (DCP), Light Weight Deflectometer (LWD), or GeoGauge (Soil Stiffness Gauge). In Europe, a Plate Load Test (PLT) is sometimes used.
  • Density Control: Each lift is compacted until a target density value is met through direct or indirect measurements; often accompanied by an acceptable range in moisture content. Field QC/QA options usually include a direct measurement of density/moisture content or an indirect measurement using a nuclear density gage. This is the most common specification currently in use.

Current specifications also commonly dictate size and weight characteristics, allowable roller patterns, and allowable lift thicknesses in either a loose or compacted state.

Soils IC Specifications

The first intelligent compaction specifications were established in Europe in the early 1990s, and the US first adopted IC specifications in the mid-2000s.

Current IC specifications for these material types generally follow one of the following two approaches:

  • Field calibration of IC roller measurements to either stiffness or moisture/density test data using test beds.
  • Identification of weak areas for assessment with conventional QC/QA methods (e.g. moisture/density or stiffness).

The following is a timeline of specification development for IC of soils. They are also applicable to aggregate subbase.

United States National Guidelines

  • FHWA Generic Soils IC Specification
  • AASHTO PP81-14 IC specification (for both soils and asphalt)

Download US State DOT IC specification from the At-a-Glance table.

For further information, please refer to the specifications literature in our online collection of IC resources.