What is Intelligent Compaction (IC)?
Intelligent compaction (IC) is a roller-based method that measures the stiffness of the material being compacted and maps it with GPS. Crews use it while they build a subgrade, base or asphalt layer, not on the finished pavement.
What the roller carries
An IC roller is a normal vibratory roller with added instruments. A GPS antenna locates the roller. An accelerometer measures the drum acceleration, which is the reaction of the compacted material to the drum. For asphalt, infrared sensors measure the surface temperature. A display in the cab gives the operator a color-coded map of roller passes, stiffness and temperature. The system stores the record for later download (FHWA, 2013 and 2017).
What the value means
The roller reports stiffness, not density. FHWA calls the calculated values intelligent compaction measurement values (ICMVs). No standard method exists, so each manufacturer calculates its own. FHWA sorts them into five levels, from empirical frequency ratios (Level 1) to dynamic models (Level 4), and describes Level 5 as still under development.
An ICMV is not a spot test. Its footprint is about 2 m by 0.3 m, and its influence depth is about 0.5 m to 1.6 m. The roller speed, the vibration settings and the soil or asphalt mix change the result.
What it is used for
FHWA lists 100 percent surface coverage and a record of each pass. It also lists the finding of weak spots and of areas that miss the target compaction level. Areas that fail can be reworked before the next layer goes on.
Airfield construction
FAA AC 150/5370-10H does not mention intelligent compaction. It uses a control strip and density testing. For subgrade under pavement it gives a bracketed density of 100 percent of the maximum dry density. It also recommends a density test for each 3,000 square yards per lift. Whether a project asks for IC is a matter for its own specification.
Frequently Asked Questions
- Does intelligent compaction measure density?
- No. IC equipment reports a stiffness value, not density. Each manufacturer calculates its own value, and the values correlate with material properties to different degrees. A project that needs density must compare the roller values with spot tests.
- Is intelligent compaction part of the FAA construction specification?
- No. The text of FAA AC 150/5370-10H does not mention intelligent compaction. It specifies a control strip and density tests. For subgrade it recommends one density test for each 3,000 square yards (2,500 square meters) per lift. The geotechnical engineer sets the frequency.
- What is an ICMV?
- An intelligent compaction measurement value (ICMV) is the general name for a value calculated from accelerometer readings on a vibratory roller drum. No standard method exists, so each manufacturer has its own. FHWA groups them into five levels by the model behind them.
References
- fhwa-hif-13-051
- Intelligent Compaction, Techbrief (FHWA-HIF-13-051) Federal Highway Administration
- fhwa-hif-17-046
- Intelligent Compaction Measurement Values (ICMV): A Road Map, Technical Brief (Summer 2017) Federal Highway Administration
- faa-ac-150-5370-10h
- AC 150/5370-10H, Standard Specifications for Construction of Airports (12/21/2018) FAA
This is a reference entry. TarmacView provides drone inspection services and doesn't sell the equipment or materials described in this glossary.
