Intelligent Compaction

OEMs hope new IC technology can replace assurance testing in the construction of asphalt pavements

More than mere lines on a touchscreen, intelligent compaction (IC) systems have evolved during the past few years to something that involves complex software and equations working “behind the scenes” while the roller operator works with what she can see at the operator’s platform. Most of the systems on the market today incorporate a temperature sensor pointed at the surface of the mat, an accelerometer affixed to the frame of the machine and a visual display at the operator’s station. If you’ll allow an oversimplification for a moment; where these systems start to differ is in what they display for the operator and in how they display it.

Some original equipment manufacturers (OEMs) argue that displaying a number or signal that any new or veteran worker will understand as “keep going” or “stop rolling soon” or “stop rolling now” is a wise option, while other OEMs suggest those signals are too vague for the bonus-achieving environment in which contractors work.

Rather than using what they consider loose language, the latter OEMs have developed a way to match a mat performance parameter, such as temperature or stiffness or maximum theoretical density (MTD), to its actual measurement of degrees or psi or percentage on the operator’s display screen. Rather than telling the operator to stop, the display shows the operator that the mat’s surface temperature is 180oF. The savvy roller operator knows she’s in the process of changing her title to “impact crusher” at that point.

Considering there are state association-sponsored all-morning seminars, OEM workshops and national webinars on how to use intelligent compaction, this article will be a primer on the basics of what IC systems are on the market and how to differentiate what they offer. Not all contractors need the same functionalities; not all contractors want to pay for a suite of services that fit the guy down the street. Let’s take an in-depth look at what OEMs have to say about their products and what various experts have shared concerning the applicability of some OEM future forecasting.

The new Atlas Copco intelligent compaction system is available on CC2200 through CC6200 asphalt rollers. The system is designed to simplify compaction by using the program’s real time data to alert the operator when the required material stiffness is reached.

ATLAS COPCO
Atlas Copco of Commerce City, Colo., launched a new version of its IC system during World of Asphalt. Many readers of AsphaltPro will more-readily recognize the Dynapac brand of pavers and rollers; Atlas Copco is the parent company. The new IC system from the company gives contractors real-time material stiffness readings for soil and asphalt compaction. This is to maximize operator productivity. Its touch screen capability is to make the system user friendly and convenient.

The intelligent compaction system uses a global navigation satellite system, such as GPS, to track the number of completed passes. It uses a drum-mounted accelerometer to measure the surface’s relative material stiffness. The system gives the operator immediate material stiffness results via the screen in the cab. This is to help minimize the number of passes he makes. When using the system on asphalt, it also detects the temperature of the surface of the asphalt mat. This is to help the system provide consistent, relative stiffness readings. In addition, Atlas Copco’s intelligent compaction system helps contractors detect any loose materials so they can perform additional passes to reach the right compaction.

Contractors can use the system on a tablet to set project parameters and view compaction data. Once the roller has achieved the optimal level of compaction for the project’s parameters/specs, the program alerts the operator, so he or she can stop and reduce the risk of over compaction. The data storage also means contractors have the results available to print off or show to inspectors. (Keep in mind, inspectors might still want to carve out future potholes—core samples—to double-check compaction numbers.)

The system is available on Atlas Copco CC2200 through CC6200 asphalt rollers and CA2500 through CA6500 soil rollers. Contractors can get free on-site training from an Atlas Copco representative or dealer.

Let’s summarize:
Atlas Copco’s system is called: Atlas Copco’s intelligent compaction system.
It’s available on Atlas Copco machines only.
It features a touch screen display at the operator’s station.
It uses a GPS to track roller passes.
It is designed to measure: the surface’s relative material stiffness.
For more information visit www.atlascopco.com.

The BOMAG-Oszillation system uses a horizontal force inside the drum. As Bomag has added the technology to larger weight class rollers, the applications for its use have expanded as well.

BOMAG
BOMAG Americas, which has a new headquarters in Ridgeway, S.C., not only offers its Economizer for IC, it also offers a tangential oscillation technology for a variety of rolling processes. The BOMAG-Oszillation TanGO exciter system is directed horizontally to maintain continuous ground contact. Target applications for the technology are bridge structures, close proximity to buildings, intermediate rolling and finish rolling. As Bomag has added the technology to larger weight class rollers, the applications have expanded as well.

Bomag’s answer to IC is the ECONOMIZER tool, which shows the operator when optimum compaction has been achieved. A device attached to the frame of the front drum measures stiffness of the mat as the operator rolls each pass. In real time, the device sends information to the box at the operator’s station. That box features a simple dial display. The dial is a series of numbered spaces that light up in yellow from 1 through 8; in red at 9 and 10 and beyond.  When the operator is working, the dial will light up to give an indication of compaction achieved. As he nears the red zone, he will know he is nearing the optimum density.

Because the system isn’t running advanced calculations with temperature or other elements considered, it doesn’t require any input from the project supervisor or the machine operator. No separate switching on/off or calibration is required.

Bonus: The ECONOMIZER is available on vibratory plates.

Let’s summarize:
BOMAG’s system is called: BOMAG ECONOMIZER.
It’s available for any compaction equipment.
It features a dial display at the operator’s station.
It uses a monitoring device to track mat stiffness.
It is designed to measure: mat stiffness.
For more information visit www.bomag.com.

CAT
As part of the Connected Work Site, Caterpillar® Global Paving offers the AccuGrade machine control and guidance solution. It is designed to leverage positioning technologies such as sonic, laser, GPS and ATS, to help contractors in different applications. On single drum soil compactors and double drum asphalt compactors, the system is the AccuGrade Intelligent Compaction. It uses GPS mapping and measurement. Its components include a GPS receiver, sensors, accelerometer, display and radio.

To determine when the operator has achieved compaction of the asphalt mat, the accelerometer, which is mounted to the drum, measures G-forces of acceleration. The system takes vibratory frequency and mat temperature into consideration when determining stiffness of the mat. The compaction value is displayed visually in real time for the operator along with amplitude, frequency, speed and number of passes. This empowers the operator to identify and pinpoint non-completed/uncompacted areas.

The system allows documentation of the completed work, and this feature is listed as a benefit when communicating with inspectors who would otherwise wish to perform quality assurance checks.

Let’s summarize:
Caterpillar’s system is called: AccuGrade Intelligent Compaction.
It’s available on Cat machines only.
It features a color display at the operator’s station.
It uses a GPS to track roller passes.
It is designed to measure: stiffness of the mat.
For more information, call on a local Cat dealer.

SAKAI
Sakai uses CIS2 from Topcon. It features a touch-screen display at the operator’s station to map the number of roller passes, roller speed, vibration frequency and amplitude, Sakai’s own compaction measurement value, and the paving surface temperature.
Let’s summarize:
Sakai’s system is called: CIS2.
It’s available on Sakai machines only.
It features a touch screen display at the operator’s station.
It uses a VRS network to track roller passes.
It is designed to measure: the surface’s relative material stiffness.
For more information visit a local Sakai dealer.

Caption for image saved as COA DD110B w/DensityDirect
The user interface of Volvo IC with Density Direct depicts a density map, showing each square foot of rolled asphalt in a color representing density, and also provides a real-time numerical density reading displayed in the corner of the screen.

VOLVO
During World of Asphalt in March, Volvo Construction Equipment introduced its IC for select Volvo asphalt compactors, which will be available in the fourth quarter of 2015. There will be two packages — Volvo IC and Volvo IC with Density Direct. In addition to offering the pass mapping, temperature mapping and data storage features of the Volvo IC system, Volvo IC with Density Direct includes the industry’s first real-time density mapping technology.

Within the Density Direct system is a calibration screen, where the user sets the target density for a project. Once fully calibrated with data specific to the application, the Volvo IC with Density Direct system produces a density calculation that the manufacturer states is accurate to within 1.5 percent of core sampling, providing a real-time reading of density values over 100 percent of the mat.* The machine also “saves” the calibration settings so operators can assign calibrations to certain elements of a job, and switch back and forth between settings as needed. With this real-time data, the operator is given the chance to make any necessary adjustments while asphalt is being paved.

The user interface of Volvo IC with Density Direct depicts a density map, showing each square foot of rolled asphalt in a color representing density, and also provides a real-time numerical density reading displayed in the corner of the screen. Both Volvo IC and Volvo IC with Density Direct offer real-time temperature and pass mapping data. Using the 8 by 10-inch color monitor of the Volvo IC system, the pass mapping function captures each compactor pass and drum overlap with an individual color, so that the operator can see gaps and work to maintain uniform coverage. Temperature mapping provides the operator with a picture that shows the path of the compactor overlaid with the last recorded surface temperature.

Data gathered from pass mapping, temperature mapping and density mapping is stored on the IC system’s internal 14 GB hard drive, which provides enough space for approximately seven months of data logging. Data can be backed up to USB drives in VEDA format — the Freeware system promoted by the Federal Highway Administration (FHWA) for IC systems.

With optional Differential GPS, the data gathered from Volvo IC is linked to location information accurate to within 0.5 inches, and both Volvo IC packages meet state DOT and FHWA requirements for IC specs, according to the manufacturer.

Let’s summarize:
Volvo’s system is called: Density Direct.
It’s available on Volvo machines only.
It features an 8X10 touch screen display, which can be folded up to the ceiling of the operator’s station.
It uses a GPS to track roller passes.
It is designed to calculate: density of the mat.
For more information visit www.volvogroup.com.

Footnote
*Density Direct was developed and tested as part of the FHWA Highways for LIFE Technology Partnerships Program. The technology was used on various full-depth and overlay asphalt pavement projects and later evaluated by independent users at sites throughout the country. The results were overseen by University of Oklahoma researchers and showed that Density Direct calculations were proven to be within 1.5 percent of core samples every time at 180 test locations.