Nationwide research is firming up the case for “intelligent” compaction (IC), a construction method three decades in the making that could save billions of dollars a year in potholed roads, cracked bridges, broken dams and blown-out tires. But as it represents a huge cultural shift in project delivery, the industry is struggling to find a standard way to roll it out.
With today’s busted public budgets, IC is a promising tool with global implications. “I’ve studied where we spend money in the U.S. to fix our infrastructure, and a lot of the cost can be tied directly to the performance of compacted materials underneath our civil infrastructure,” says David White, a professor at Iowa State University, Ames, and director of the school’s Earthworks Engineering Research Center. White underscored his point at an Intelligent Construction for Earthworks conference of about 100 public and private engineers, held on April 14-16 in West Des Moines, Iowa.
As the talks revealed, national research is well under way to implement smarter compaction methods, which could cut construction costs and double the life of infrastructure, panelists said. White estimates that the stiffness of soil, sand and aggregate—the building blocks of road embankments, building pads and bridge abutments—cost the public up to $100 billion a year if not built up properly. “There is something like $50 billion a year for vehicle maintenance because of poor road conditions,” he says. “Those poor road conditions are tied to what they are sitting on.” At the very least, improper compaction costs taxpayers $1 billion a year in wasted diesel fuel, construction labor, equipment maintenance, rework, rehabilitation, litigation and other inefficiencies, White adds.
IC in its simplest form is an onboard measuring device that allows roller operators to see whether they are overcompacting, undercompacting or right on target in soil, aggregate and asphalt. Some machines go another step by automatically changing frequency, amplitude or other characteristics of the drum. How users define “intelligence” is still up for debate, but the construction industry is investing millions of dollars a year to validate IC as generally accepted practice.
Government agencies are working to write specifications so they can let contracts enabling IC. So far, Minnesota is the only state to do so, though its specification is still under regular revision and is careful not to mandate IC due to the high up-front cost to contractors. Even so, nationwide, “all the cards are in place” to implement IC, says Mike Adams, a geotechnical engineer in Federal Highway Administration’s McLean, Va., research office, adding, “I’m really impressed by this.” At least a dozen states are testing IC as research spans the U.S.
Originally pioneered and adopted as standard in Europe to help extend the life of roads and to protect roller operators and their equipment from unwieldy vibrations, IC is starting to bring closer together civil designers and builders in the U.S., much like how Building Information Modeling (BIM) has taken vertical construction by storm. As such, IC’s inherent growing pains are similar to BIM’s.
Though it has been available in some form for about 30 years, IC in the U.S. recently has grown out of automated machine guidance (AMG), which grew out of the increased use of the Global Positioning System. Implementing IC, much like its more widely adopted sister technology, AMG, is nothing short of a paradigm shift. One continuing problem is the lack of three-dimensional data files needed to plug into the “smart” machines.
“Traditionally, [designers] have been giving slices of bread, and the contractors have to put it back together,” explains Corey Johnson, a solutions engineer for software maker Bentley Systems Inc. “They want the loaf.”
IC is yet another slice in the civil engineer’s loaf of bread. It puts roller operators directly in charge of ground control, enabling them to inspect their own work before turning it over to the owner for verification and payment. The increasing use of IC on experimental highway projects over the past five years is steadily giving...