According to Caterpillar, the AccuGrade Compaction for Soil Compactors system provides contractors with increased production, because their roller operators are able to determine when required work has been completed and thus move on to areas that need compaction.
Officially the Bomag BW190AD-4 AM, the 78-inch-wide tandem vibratory compactor has earned a more affectionate handle among the asphalt-paving crews employed by Indiana's Milestone Contractors.
"We just call it, 'The Smart Roller,'" says company superintendent Eddie Breeden. Smart, indeed. The AM on the model's designation represents Asphalt Manager, a Bomag product offering as part of the Intelligent Compaction (IC) movement into North America, based on technology established in Europe more than a decade earlier.
With an established tandem vibratory compactor product, passing over a test strip will define for the operator the number of passes needed for proper compaction, based on an assumption there will be no deviation in the material, rolling pattern or roller speed. With the new Bomag system, the control test determines an energy measurement that correlates with the specified density to be achieved over the complete work area. As the BW190AD-4 AM moves along, it automatically adjusts the output energy the front drum is exerting into the work surface, via a process of "vectoring" or changing the angle of energy delivered from the drum: a straight vertical angle for softer areas; a more horizontal angle as the material stiffens.
The Bomag BW190AD-4 AM was introduced to users in the United States in 2005, the year Breeden's paving crew with Milestone Contractors was working on Interstate 70 at Richmond, Ind., near the Ohio border. Bomag dealer Southeastern Equipment brought out a demonstrator model for the crew to try. "The Smart Roller" not only remained for the entire job, says Breeden, but Milestone bought that very piece and it remains part of the company's fleet today.
"The thing about it is, density comes and goes as you're going down the road or the runway or whatever," says Breeden, who's been with Milestone for 39 years, "and this machine can sense when you need a little more or a little less. The front wheel will go from beating vertical, up and down, and it'll starting going where it's more like oscillating, front to back, and that keeps it from over-compacting the mix. The machine will actually tell you when it's as hard as you're going to get it."
For the roller operator, guesswork has been replaced by the confidence that the machine is achieving with IC on auto what company quality-control personnel will be looking for when they come along with their TransTech pavement quality indicators. "The roller operator knows before he even checks it that he's getting what he wants to get," says Breeden.
In Colorado, United Contractors has likewise found the double-drum BW190AD-4 AM to be of great benefit to the quality-control process, says Ken Dobey, formerly highway superintendent and now Southern Area construction manager for the company. United Contractors likewise put one of the AM machines to work right away in 2005, and "I liked it so much, we added another one to my crew," the next year, says Dobey. "They give us a lot of options on our jobs; we have used them with several different mix designs. If we're trying to compact really tender mix, we can adjust those machines to fit the mix. We've had mixes where we have only run the front drum, because the front drum is the only one that does direct-vibe, the Intelligent Compaction part."
Dobey had gotten to know and trust Bomag Americas national accounts manager Chuck Deahl through various training classes, and thus jumped at the opportunity to test the BW190AD-4 AM in 2005 with the support of local dealer Power Equipment Co., "and we were sold instantly," Dobey recalls. "After testing like we did at first, we now run them in auto all the time."
Other approaches
Smart technology was right at home amidst the iron when the compaction and paving industries gathered March 10–12 in Orlando, Fla., for the World of Asphalt 2009 trade show.
Sakai demonstrated for the first time at the show its Compaction Information System, applicable for asphalt and soil projects. With "a simple touch-screen control pattern for quick and easy access," the new Sakai system links to a GPS system to provide the operator with real-time compaction information. This, says Sakai, enables the operator to develop a consistent roller pattern, which is viewed immediately at the operator's station via a color-coded monitor. It also provides a visual display of where additional passes may be required.
With the Sakai compaction information system, site-plan files can be uploaded into the on-board computer via a laptop, thumb drive or external hard drive, from which a compaction plan is developed for the project. At the end of the process, operators can print out a project report or download the information back to the laptop or other external drive for later transfer to an office computer for further analysis. Site plan or not, the system can be easily operated in real time by the operator, says Sakai.
Sakai's mainline hot-mix rollers feature the on-board ExactCompact system, which enables roller operators to maintain impact spacing. The operator simply sets the push-button control for the desired target figure — anywhere between 8 and 20 impacts per foot. When the machine runs, the target appears on a display, allowing the operator to reset as needed.
Other roller OEMs have introduced smart solutions to their product offerings:
- Caterpillar's AccuGrade Compaction for Soil Compactors product leverages GPS technology for measurement and mapping. Compaction values are displayed on the data display as a graduated color scale, calibrated to match characteristics of the soil being compacted, says Caterpillar. Once the value color of the work completed matches the target color, the operator can confidently move on to the next work area. Other data that can be displayed include the number of passes completed, allowing verification of the work done.
- Now part of the Volvo Construction Equipment product line, the former Ingersoll Rand tandem asphalt compactor line established automatic vibration control, which ensures drum vibration only occurs at appropriate times. Volvo's HFA models will, by altering oil flow through the hydraulic pumps, automatically adjust vibration frequency to the optimum level in each of the eight amplitude settings available, as compared to operating with a fixed vibration frequency. The HFA's built-in control system extends to automatically lag vibration on the trailing drum, so that both drums begin to vibrate at or near the same point on the surface.
- While not an IC product, the Hamm HD O130V introduced at Conexpo-Con/Agg 2008 extended the Hamm Oscillation technology to the 84-inch roller market. The HD O130V is the largest model in North America to incorporate "non-aggressive" Oscillation technology, which uses horizontal rather than vertical force to compact. The drum never leaves the mat, and both the surface and operator avoid pounding. The movement changes its direction of effect during one turn, generating an oscillating or rocking movement of the drum.
In Colorado, hands-on use of the Bomag BW190AD-4 AM quickly sold United Contractors on IC.
"We did a little testing with them on roller passes on different mixes," says Dobey. "We ran them in manual and we ran them in automatic with the computer running, and we found that running manual, same number of passes, we wouldn't get the quality of compaction that we would running them in auto. We were actually over-compacting in manual; we were pounding too hard. The machine would back off in automatic and it would bring our densities up. We also found in some mixes we could cut a roller pass running them in automatic."
Once a company and its crew foremen buy in to a technology, says Dobey, it doesn't take long for the operators, even the most cynical veterans, to jump onboard. "It's a simple process; the training's not hard on them," he says of Asphalt Manager. "Just getting people to understand what the rollers are doing, what their potential is, that's a huge part of it. After you can get that across with your roller people, do a few tests with them, they understand.
"I had a guy who had 20 years on a roller when we started using these. He was pretty stubborn, he always could 'roll better than any computer.' But after we did some testing, he bought-in hook, line and sinker. Right away, he was, 'We're only going to run them in auto,' because he saw what they did. Those machines are just a huge tool for our operators.
"We have one full-time highway crew that runs the two 190s all the time," says Dobey. A second United crew is dispatched to highway jobs if needed, but can't always get a BW190AD-4 AM on rental at that point, "but if we had two full-time highway crews, that's what they'd be running."
In Indiana, "I don't know if a company our size needs any more than one of them; maybe two at the most," says Milestone's Breeden. "But I really think that a company ought to have one if they're going to do all the kinds of work we do. If you getting into a pickle on a job, get that roller there, and it's something to help you get away from penalties and so forth."
Breeden had his fingers crossed that a couple of Interstate jobs will come to fruition for his crew in 2009, meaning it should retain use of the company's "Smart Roller" for the year. "I think it's needed in the industry," he says, "and I'm glad we got one."
Dobey is intrigued by Bomag's plans to add a 66-inch Asphalt Manager model, "and I'd like to see them in a parking-lot version, too," he says. "It's just such a good tool."
