How Does Intelligent Compaction Work?

IC rollers are vibratory rollers equipped with instrumentation fed to a documentation and feedback control system that processes  compaction data in real time for the roller operator.

Instrumentation

The precise location of the roller, its speed, and number of passes over a given location are mapped using the Global Positioning System (GPS) or a similar system.These mapping systems are commonly used to establish grade and to control other pieces of equipment.

To determine the effectiveness of the compaction process, compaction meters or accelerometers are mounted in or about the drum to monitor applied compaction effort, frequency, and response from the material being compacted. The methodology used to calculate material response is often proprietary. Soil response can be described by a compaction index or stiffness/moduli values. Project test strips are often calibrated in order to correlate the compaction index or stiffness/moduli values to conventional in situ measurements such as material modulus or density.

Additional temperature instrumentation for asphalt IC rollers allows the user to monitor the surface temperature of the asphalt pavement material. This is critical as vibratory compaction within certain temperature ranges can cause adverse effects.

Documentation and Feedback Control

One critical feature IC rollers possess: a system to collect, process and analyze the measurements in real time. This feature allows the roller operator to view acolor-coded map that instantly displays interaction between roller location and number of passes, cumulative compaction effort, and material response. Optional feedback controls can utilize this data to continuously adjust the force and frequency of the drum in order to maximize efficiency and effectiveness. The display on the IC roller alerts the operator when the desired compaction is obtained, eliminating unnecessary passes. If problem areas are detected, the system will notify the operator when additional roller passes will not result in desired compaction. It will then document the problem areas for further analysis.

Some IC rollers – namely some dual drum rollers for asphalt pavement materials – are not equipped with accelerometer-based measurement systems. However, there are still many benefits from collecting the IC roller pass data and asphalt mat temperatures.

Further reading: FHWA-Transportation Pooled Fund: Intelligent Compaction Final Report