If you’ve driven certain newer-model cars, you may have encountered some interesting technology to help with certain driving chores. These cars have features like lane departure warning systems to help you stay on course, or intelligent parking assistance when you’re trying to parallel park. Similarly, technology can bring new capabilities to paving equipment that help improve the quality and efficiency of road construction activity. In this edition of the RoadReady newsletter, we’ll look at Intelligent Compaction, a collection of roller features that can be used to monitor and adjust the compaction process.
Intelligent Compaction Features
Intelligent Compaction (or IC for short) refers to a group of features integrated into a system that provides real-time measurement and control of the compaction process. The IC technology is sometimes also called “continuous compaction control.” Common equipment on an Intelligent Compaction roller, depending on the system, may include:
- Accelerometers and a highly accurate GPS to track machine-ground interaction and the position of the roller
- Infrared temperature gauges to monitor the temperature at the ground surface
- A computer with a dedicated software program that processes compaction data and reports measurement values
- Display readouts and controls to give feedback to the roller operator and allow for adjustment of compaction operations
In building a pavement structure, Intelligent Compaction can be applied both to unbound materials (bases, subgrades, and embankments) and to asphalt pavement layers. The primary use of IC is with vibratory rollers, including steel wheel rollers for asphalt paving and either smooth drum or sheepsfoot rollers for soil compaction. The features used to provide IC are generally well-developed, mature technology and are available from a number of different manufacturers, both on new roller models and as retrofits on existing rollers.
Benefits of Intelligent Compaction
Intelligent Compaction equipment can help identify and address potential problems during compaction, such as weak soils in a subsurface layer or temperature differentials in an asphalt mix. Operators can monitor compaction performance to reduce variability in the material and achieve more uniform density. By monitoring machine-ground interaction, the IC equipment can control the intensity of roller vibrations to avoid potential damage to the pavement. In addition, GPS capability makes it possible to track each pass so that roller patterns can be more precise and the right amount of compactive effort can be applied.
Throughout the compaction process, IC equipment measures and documents the work to create a complete record of compaction effort. The measurement values used in Intelligent Compaction focus on material stiffness, and the methods for calculating these values depend on the equipment manufacturer. As a result, compaction measurements using IC do not translate directly into density readings for quality control and quality assurance purposes. However, IC measurements are still considered meaningful indicators of the level of compaction.
Intelligent Compaction Costs
Not surprisingly, implementing Intelligent Compaction does involve some costs, so these should be evaluated before deciding to move forward with an IC system. Depending on the features and the manufacturer, an Intelligent Compaction roller may cost 3-5% more than a conventional roller, and retrofitting an existing roller with IC equipment can see costs ranging from $50,000-$75,000. In addition to the upfront costs, IC equipment will periodically require maintenance and calibration. Roller operators and supervisors should also be trained in how to use the technology.
These costs can be recovered in a number of ways. By facilitating more efficient roller patterns, Intelligent Compaction can lower fuel usage, which both saves money and benefits the environment. Optimizing compaction can also shorten the time needed for construction, leading to reduced costs for labor and equipment. The ability to identify compaction problems in the material allows corrections to be made before additional layers are placed, minimizing costly rework and leading to improved pavement performance. Finally, although IC equipment does not measure density directly, it may help contractors achieve more uniform compaction and collect larger contract pay incentives related to target densities.
The Road Ahead
Overall, a roller with an Intelligent Compaction system won’t necessarily pay for itself right away, it may take a few projects to reach that point. Like the newer technologies in cars that reduce gas usage, the payoff comes over time. The technology is continually improving to help achieve better performance, even if we aren’t to the point of self-driving cars (or self-operating rollers) yet. For paving projects, Intelligent Compaction is another valuable tool to consider for building high-quality roads.
Federal Highway Administration, Accelerated Implementation of Intelligent Compaction Technology for Embankment Subgrade Soils, Aggregate Base, and Asphalt Pavement Materials: http://www.fhwa.dot.gov/pavement/ic/pubs/hif12002.pdf
Federal Highway Administration, Techbrief: Intelligent Compaction: http://www.fhwa.dot.gov/construction/pubs/hif13051.pdf
National Cooperative Highway Research Program, Report 676, Intelligent Soil Compaction Systems: http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_676.pdf
Minnesota Department of Transportation, Intelligent Compaction Implementation: Research Assessment: http://www.cts.umn.edu/Publications/ResearchReports/pdfdownload.pl?id=940
Center for Transportation Research and Education, Field Evaluation of Compaction Monitoring Technology: http://www.intrans.iastate.edu/publications/_documents/t2summaries/compaction_2.pdf