Intelligent Compaction [PDF]: Benefits and Limitations

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Intelligent compaction is the compaction of road materials, such as the layers of soils, aggregate bases, or asphalt pavement materials, using advanced vibratory rollers armed with a unified measurement system, a computer reporting system, GPS-based mapping, and Optional Feedback Control (OFC).

When we talk about road construction, compaction is considered one of the most critical processes in pavement and roadway surface construction. It is necessary to attain high quality and uniformity of pavement materials, which in turn better ensures the long-lasting performance of the road.

Compaction, in the simplest terms, is the exertion of force on something so that it becomes denser. In contrast, Intelligent Compaction(IC) renders the technological means(an IC roller) to ensure that compaction is performed consistently, thoroughly, and accurately.

The use of IC rollers assists with real-time compaction monitoring and periodic adjustments to the compaction process by combining documentation, measurement, and control systems.

In addition to this, IC rollers are also capable of maintaining a continuous record of color-coded plots. With this, the user can view the plots of the precise location of the roller, material stiffness measurements, and the number of roller passes.

Intelligent Compaction requires the perfection of the following systems:

• Precision mapping
• Pass Count tracking
• Compaction control 
• Temperature mapping 
• Documentation of quality assurance and quality control. 

Precision Mapping

Precision Mapping uses satellite data to make rollers more efficient.

Firstly, the position of the roller is established through Global Positioning Satellites(GPS). A GPS antenna is commonly mounted on top of the roller’s cabin.

The GPS then enables Precision Mapping, which allows operators to raise productivity by working on the most efficient rolling pattern. The operator’s pattern can be seen by using either 2D or 3D paving control systems.

The control box for these systems comes with graphical displays with adjustable light settings for both day or night paving.

Pass Count Tracking

Pass Count Mapping keeps an eye on the number of passes over an area and adjusts the effort to avoid over- or under-compaction.

Pass Count Mapping utilizes a control box, a roof-mounted GPS receiver, and a Connected Site Link.

The system computes the machine's position and displays a color map and scale, indicating the present number of passes and where the operator has gaps or overlaps.

Compaction Control

With compaction control, one can achieve a consistent compaction to target the specified design density.

Real-time view monitors and detects where compaction does not meet target specs and immediately prompts the operator while saving the data to the cloud.

Nowadays, Compaction Control systems use an accelerometer to measure Compaction Meter Value(CMV), Compaction Control value(CCV), Resonance Meter Value(RMV), Frequency, and Amplitude.

Compaction Control systems are compatible with all kinds of asphalt compactors. The accessories(wiring harness and brackets) are permanently installed in a way so as to complement the machine body. These components can also be used on different paving and earthmoving machines to increase utilization.

The Compaction Control system records and shows machine position, machine pass count/coverage, asphalt temperature, compaction measurements, vibratory frequency, compaction width, and machine speed.

Temperature Mapping

Infrared Temperature Mapping helps with measuring the real-time surface temperatures, thus enabling the operator to find the optimal window for compaction.

Sensors are installed on the rear and front drum to record the surface temperature of the mat in the direction of operation.

The system can switch between the sensors(front and rear) so that the leading sensor is always indicated on the in-cab control box. The operator is able to see accurate temperature information of the asphalt surface about to be compacted, before the temperature drop caused by the wet steel drum passing over the hot mat.

Documentation of QA/QC

The data recorded through the systems can be wirelessly transferred from the machine to the office for analysis using web-based fleet, asset, and productivity management solutions. This technology generates electronic data of results, allowing post-process quality control and analysis that can be viewed on any desktop or laptop computer.

Benefits of Intelligent Compaction

• Given a good correlation between the dynamic measuring value (i.e CMV, CCV, etc.) and the required properties of the compacted soil, there is potential for both reducing the compaction energy and possibly also the number of roller passes without detrimental effect.
• Over-stressing caused by an excessive number of passes or excessive vibration will be minimized by the use of intelligent compaction. For example, with non-cohesive soils such as sands(particularly single-sized), overstressing can occur in the near-surface material.
  With cohesive soil, after the minimum air void content is reached, some of the compaction stress may generate excessive pore water pressure immediately below the compactor, causing softening.
• Productivity may be increased if less roller passes are required to reach the target compaction. This has an associated cost-benefit, particularly for larger earthwork schemes.
• The number of independent spot tests of soil properties such as density and stiffness may be significantly reduced. Tests of this nature, which are often undertaken when using conventional rollers, are time-consuming and costly.
• Soft spots in the compacted material can be readily identified and either subjected to further compaction or replacement to provide a layer of more uniform stiffness. Spot tests using conventional stiffness testing techniques may fail to identify soft areas.
• Incorporation of GPS into the equipment is considered invaluable, as even when compacting earthworks to a method specification, the documentation system will provide proof of the number of roller passes and mapping of the areas that have been compacted.

Limitations of Intelligent Compaction

• IC or compaction monitoring systems may be more effective in controlling the degree of compaction in certain soil types. Current indications are that compaction of granular soils will be more effectively controlled than will the compaction of clayey soils. The latter will need particularly careful evaluation at the trial or calibration stage.
• Vibrating rollers with IC or compaction monitoring systems are more costly to purchase(and hire) than conventional compaction plant. There are also some maintenance costs in ensuring the electronic equipment continues to operate satisfactorily.
• Operator controls and displays vary considerably according to the machine manufacturer and adequate operator training is therefore essential. Training needs extend to the downloading of the machine data using the documentation system(if present) and the preparation of interpretative graphics for the client.
• Site trials and or the set up of calibration areas are likely to be required at each construction site in order to determine the respective dynamic measuring values applicable to each soil type encountered. This would not be cost-effective for small projects.
• The quantity of data produced by the onboard measuring system is likely to be large and investment in an efficient data management system is required.

Frequently Asked Questions

Read more: Dynamic Compaction: Advantages, Purposes, and Uses
Read more: Effects of Compaction on Soil Properties
Read more: Different Types of Soil Compaction Equipments -Types of Rollers