Construction industry experts say many contractors are now utilizing available technology for compaction to augment the “old school” approach of “skill and touch.”
Tim Kowalski, Hamm application support manager for Wirtgen America, says he believes the use of “skill and touch” has gone by the wayside because the technology of rollers has advanced so much.
“Years ago, the seasoned veteran could tell by the seat of their pants when enough rolling was done,” he says. “Nowadays, you try to isolate that feeling from the operator to the machine so they’re more comfortable. With the intelligent compaction, we’re hoping that’s the next step to help them become a better roller machine operator.”
“Today, contractors can’t do it the old school way—maybe smaller contractors can—but regulations are being written around intelligent compaction,” says Dann Rawls, marketing consultant for Caterpillar’s technology enabled solutions group, adding that a few dozen states have now done so.
“Typically in the past, if I was putting in a lot of dirt in building up this road, I would really only have to take one density test for every 250 cubic yards of dirt. That’s a type of requirement when you’re doing state and federal work. That density test represents about a square foot of material,” he says.
In essence, that approach is testing a small percentage of the actual material being put in, adds Rawls.
“Now we get 100% testing of all of the material,” he adds. “The operators get a map in their app display. They can see where the roller has been, map those stiffness values and then if they see areas that don’t match the other areas, they can focus their testing guys to that spot to remediate it before they put pavement on it. It’s very cheap to fix something at that point and very expensive to fix after you put pavement on it.”
Newer technologies are offering better consistency throughout the job, points out Rawls. Systems such as the MDP and CMV are useful tools, especially in warranty work and design-build-finance-operate and public-private partnership projects, he adds.
“There’s a lot of exposure out there on the back end of a road job,” he says. “It’s good documentation and a good tool to get consistency.”
“Contractors are interested in on-board compaction gauges primarily to protect their investment,” notes Vince Hunt, product application and training specialist for Wacker Neuson. “Competec alerts the operator via flashing lights when over-compaction has occurred. The LED indicator also gives feedback regarding maximum compaction for the particular material that is being compacted.”
That said, there is no substitute for experience, says Hunt.
“Skill and operator judgement will always be crucial in achieving proper compaction,” he adds.
Given mandated compaction specifications, the question is whether contractors have all of the technology needed to meet them.
“Primary metrics measured include rebound detection and stiffness. Measuring stiffness is said to be a better indicator than density,” says Katie Pullen, brand marketing manager, CASE Construction Equipment. “If a company strictly goes off of the data from a nuclear density meter, they’re not getting load-bearing capabilities. A nuclear density test is still required, but it will be more accurate and there will be a higher chance of passing if intelligent compaction is used.”
For jobs involving mandated compaction specifications, a third party is almost always involved in the final determination of compaction values, points out Hunt.
“The tools used by soils experts such as the nuclear density gauge, geogauges, and other devices to measure relative compaction are still indispensable and will always be used for a final determination of the measured compaction,” he adds.
Areas of lack include education and proper machine selection, adds Hunt.
“Proper machine selection for the given application is very important,” he says. “In addition, following basic construction techniques is always crucial.”
Despite the different specifications from state to state, a machine is the same no matter what state in which it is used, points out Kowalski, adding the challenge is getting state officials to better understand what the equipment can do for them.
“In the next three to five years, you’re going to see intelligent compaction become more of a standard in the industry than to be put out on demo or pilot projects because the feds are really pushing the states to start implementing this into their programs and projects,” says Kowalski.
“There are 33 states involved with intelligent compaction and 22 of them currently have some kind of a specification, whether it be on the soil side or the asphalt side and are using them on projects,” he adds. “This year alone, we’re probably going to see more than 200 projects in the US.”
The driving factor comes in the acceptance of the concept that there is a difference between stiffness and density, points out Kowalski.
“Stiffness is more of a resistance of the material where density is the final result of compaction,” he says. “It’s like comparing apples and oranges. What they’ve found out is because we can map our paths out and measure temperature, we’re getting more consistent on our roller patterns and staying within a certain temperature range, so we naturally should get better density across that, smoother rides, and longer lasting roads. There’s where you see the big benefit.”
In his view, today’s technologies are “long overdue,” notes Rawls.
“I always ask contractors ‘When is the best time to plant the tree?’” The answer: 20 years ago, because you can sit under it and enjoy the shade,” he says. “I can associate these road failures we’re seeing to the compaction map and make clear conclusions between inconsistent base and road failures.”
Not much attention had been paid to the load bearings underneath the surface, says Rawls.“The testing methods were inadequate,” he adds. “They weren’t testing enough of it to really quantify. The new technologies are good for the industry, good for taxpayers, good for everyone. Roads will last longer and we can fix the ones we need to be fixing.”