When Ron Larson started nine years ago as a construction project manager for the Oregon Department of Transportation, intelligent compaction was an unknown concept.
Then in 2016, his agency began some IC pilot projects. As with other states, Oregon discovered that intelligent compaction improves paving. The ODOT now requires IC on all its major highway paving projects.
“We’ve come a long way quickly,” says Larson.
More than 300 projects using intelligent compaction have been completed in the United States since 2000, says Pavana Vennapusa, the lead engineer at Ingios Geotechnics, which outfits vibratory rollers with IC technology.
All major manufacturers of paving and milling machines make some version of the technology, which consists of an integrated measurement system, an onboard computer reporting system, Global Positioning System (GPS) mapping, and optional feedback control. The technology has not only improved results during the day but makes night paving much easier.
“Most of the paving, such as the overlays, happens at night,” says Vennapusa. “It’s one of those growing markets. And one of the cool things with using intelligent compaction is, because of the integrated GPS, you can visually ‘see’ where you’re at – with that screen in front of you.”
Though IC is still not as widespread as he’d like, he believes in time it will be.
“The intelligent compaction for paving, including night and day paving or road construction, is not going away. The frequency of its use on projects has gone up over the past decade, and it’s only going to go up. Many DOTs are moving toward writing intelligent compaction into specifications.”
He says those competing for paving jobs will have to ask themselves, “So, do you want to be a contractor who wants to have an edge over others in bidding those projects, or not?”
Contractors using IC first select the technology to gather the data, which is then processed and displayed on a screen. On a tablet-like device, compaction progress appears almost as painted swaths.
“It’s like using an Etch A Sketch that has a wide crayon, if you will,” Vennapusa says. “First pass is one color. Second pass is another color; third pass is whatever color you want.”
With IC handling some of the operators’ tasks, “they can pay attention to the technical parts of what they’re doing. They control the frequency and the amplitude and the vibration, and they do that in part by a feel that they get from the asphalt,” he says. “In addition, they can look at the frequency and the amplitude and what’s the response in the stiffness of the mix.”
Project managers, foremen, superintendents, engineers, contractors and others can monitor the operators’ roller work in real time from their smartphones.
And once operators finish the quick learning process for IC, he says, they’re sold on it.
“They’ve all told me, ‘I will never operate a roller again without IC. Give it to me. It helps me to do my job.’”
IC helps operators focus, gives edge
The Oregon DOT joins Minnesota, California, Missouri and Texas transportation departments as national leaders in the use of intelligent compaction.
“For all paving everywhere, not just for DOTs but for counties, municipalities, even down to parking lots, it just makes sense to use technology to prove that we do have good, uniform quality,” Larson says.
That same quality and uniformity can be achieved at night, where operators don’t have the same visual indicators they have during daylight.
“We know we have to roll over the asphalt a certain number of times to achieve the target density. So at night, that’s even harder to do when you can barely tell between the dark asphalt and the night background, and try to tell where you’ve been,” says Kevin Garcia, business area manager for Trimble Paving Solutions. “To have an intelligent compaction system to tell the operator you rolled this area this many times and this was the target, and you saw it was X-number of passes, becomes hugely valuable to people.”
The IC systems use vibration sensors, and the software systems display compaction values, GPS locations, pass count and thermal scanning results. The roller operator can look at average asphalt (mat) temperature that he or she is rolling, as well as pass count and speed.
When simply relying on the operator’s vision, it can be difficult at night to spot markings spray-painted on the ground for asphalt depth and slope. That can lead to placing too much or too little asphalt in a location. But with 3D technology on the paving screed, the operator relies on the software system to automatically direct the depth and slope of the paving screed.
Thermal imaging can then measure the temperature at laydown, the GPS location of the machine and the paver’s speed.
“Knowing your temperature is critical because it allows us to ensure that we’re achieving compaction in the appropriate window,” says Garcia. “Rolling too hot isn’t effective. Rolling too cold isn’t effective. Both of them can be detrimental to the finished surface.”
At the Missouri Department of Transportation (MoDOT) last year, IC was tested for roller coverage along with infrared scanning (IR) for temperatures and Veta software. The demonstrations were at 13 field sites in a year-long pilot.
The results were so successful that MoDOT says it will fully implement IC in its highway projects by 2021.
“We believe that by using IC for projects, we’ll have a better way to work with contractors on getting appropriate coverage,” says MoDOT research administrator Bill Stone.
Assisting MoDOT were paving engineering specialists with The Transtec Group, based in Austin, Texas.
IC and IR work independently of each other – so other DOTs and contractors interested in using the technology don’t need to invest in both.
“Our recommendation is to use both IC and IR,” says Dr. George Chang, Transtec’s director of research and leader of support for the IC-IR demonstration project. “Leveraging both technologies on the same project can really enhance the quality. The technologies complement each other.”
Capital Paving and Construction in Columbia, Missouri, was the contractor on four of the field projects.
“It is one thing to learn about how to do something in a classroom setting, but until you actually get everything set up and going down the road, it’s hard to really understand and get things to work correctly,” says Marli Hayes, assistant project manager for Capital Paving and Construction. “Transtec bridged the gap from taking the information in the classroom to applying it to the field and really understanding the IC-IR programs in a useful way.”
Whether paving at night or in the day, IC can also help your bottom line by getting work and repairs done quickly and correctly.
“If intelligent compaction data is properly validated, you actually can identify whether your design assumptions are being met in the field or not,” says Vennapusa.
“This technology gives you an opportunity to see defects in real time, and you can fix them,” Vennapusa adds. “You have a much more uniform foundation. And then when you put concrete or asphalt on top, it will perform much better than if you would still have defects.”
Vennapusa, a former assistant director at Iowa State University’s Center for Earthworks Engineering Research, has written more than 50 articles and papers on topics ranging from earthwork construction to machine-integrated monitoring systems, including intelligent compaction. His company, Ingios Geotechnics, outfits rollers and created an online dashboard system in which the owner or quality control engineer, for example, can log in and see what the operator is seeing live. The company anticipates soon providing a compaction information database and more services.
Ingios provides clients with a cloud-based data management dashboard tool to allow live-streaming of field compaction that simplifies the IC monitoring, tracking and data management. The tool includes features like real-time compaction monitoring (mapping) results, live-feed site camera views, asset mapping and activity, calibration status tracking, automated material sensing technology and advanced data analytics and plotting to manage incoming data.
“We’re working with several departments of transportation to assist in developing specifications. We also have written guide specifications for Illinois Tollway,” Vennapusa says. In addition, the company has been working with manufacturers.
Vennapusa says he analyzed three paving projects in Iowa that included IC specifications and found that implementing intelligent compaction to meet a project specification on average amounted to only 1 percent of the project cost.
Now, the majority of DOTs are documenting what they’re doing with IC, which can be invaluable if the data is examined in the future in relation to road performance, Vennapusa says. He and others hope they will archive the data and use it to expand IC’s use.
DOTs changing with the times
Historically, contractors have put out a roller and told the operator, “I need you to make three passes with this roller over the whole area,” ODOT’s Larson says.
The compactor operator starts, but his roller is not wide enough to cover the paving lane. So he makes multiple passes on the right edge, the center and the left edge. He mentally keeps track of where he’s been, how many times he’s been over it. He can tell where he’s been on the first pass, but not so on the second and third as it’s being compacted.
“It’s very problematic,” Larson explains. “I’ve been an inspector, and I have inspectors who work for me, and it’s extremely hard to know that all areas have been covered. I can tell an inspector, ‘Stand here. Count the number of passes at that one location.’ But how do we know that it’s uniform throughout the whole area? We don’t.”
That all changes with intelligent compaction, which paints a picture of where the roller has been.
“The touchscreen display is right in front of the operator,” Larson says. “He can see where he has already hit the number of passes and where he has yet to do that. He can also get a readout on his temperature, because if he’s too late in getting those experimental three passes, then too late means the mat has already cooled. You start beating on cold asphalt, and it just breaks apart.”
Even veteran operators love the technology, he says. “I talked with a number of highly experienced roller operators – 20, 30 years of experience – and once they learned intelligent compaction, they didn’t want to stop using the technology,” Larson says. “It’s color-coded on temperature, color-coded on spec, color-coded on the pass count and the coverage.”
The inspectors also appreciate that all the paving data is recorded instantly and can be downloaded at the end of each night.
“Our specs require that that information be provided by the next business day, so typically we’re paving from say 10 p.m. until about 5 a.m.,” Larson explains. “At 5 a.m., they finish up. That information gets downloaded.”
The information is analyzed to determine whether any corrections need to be made. “And we’re ready to go the next night with brand new data, quality control that tells you where you’ve got it done correctly and it tells you where there needs to be improvements,” he says.
That all ensures the road is being built to proper compaction levels – across the full length and width of the paving.
“We know from experience that the higher the percent of compaction, the better quality we have and the longer it will last,” Larson says. “If we don’t get good compaction, then it’s going to fall apart quicker. The asphalt won’t last.”
ODOT shoots for a 10-year life on the wearing course. Due to good upkeep and initial construction methods, the agency often adds another year of wear, achieving a 10-percent increase in life.
“There’s not too many technologies that I’m aware of where you could do a 10-percent increase just by using technology,” says Larson. “But that’s exactly what we do with intelligent compaction.”