...state departments of transportation more confidence the technology can cut construction waste and extend the life of roads and other infrastructure. Though IC likely will not render traditional inspection instruments, such as the nuclear-density gauge, obsolete, IC is in a position to grow as a 21st-century quality-control/quality-assurance tool.

So far, smart compaction machinery is turning out to be excellent for “proof” rolling, engineers say. “We are trying to measure and predict how [roads] will behave when a truck runs over the material,” explains John Siekmeier, a senior research engineer for the Minnesota Dept. of Transportation. “The roller is really a better simulation of how well that material will behave over the long term, over the itty-bitty, nuclear-density gauge.”

The instrumented rollers cost about 20% more than their non-instrumented counterparts but can pay off in the first job, proponents say. When poor compaction is found underneath graded aggregate or pavement, “$20,000 gets eaten up pretty fast” when you need to remediate, says Dave Dennison, product manager for Kewanee, Ill.-based roller maker Bomag Americas. But some contractors say they have yet to see a financial benefit, adds Rebecca Embacher, a senior engineer at MnDOT, adding, “We are hoping that the proactive contractors will take this device and do a better job.” Because contractors say they tend to overcompact to save face, the current state of practice is a guessing game. Researchers want to know if IC can turn compaction into an exact science.

Soil is a huge challenge because it is the most varying as well as most the most abundant building material in nature, says White, adding that compaction methods have not changed all that much in the past 70 years. Some see IC as a way to increase firms’ profits while helping taxpayers save. “If you can compact your embankments right, these roads will last 25 to 30 years longer,” says Dwayne McAninch, chairman of West Des Moines-based earthmover McAninch Corp.

Like building codes that embrace performance-based specifications, using IC on civil earthworks poses a twofold dilemma to contracting authorities: First, each roller measures compaction slightly differently using what typically is a patented combination of accelerometers and algorithms. Writing specs that are technology-neutral, so as not to give any supplier an unfair advantage, is tough when every machine is proprietary. Second, DOTs want to see a direct correlation between IC and performance to ensure real-world results are achieved.

“The only reason why we are going to require something like GPS and IC is because we are confident that it is going to produce savings to the taxpayer,” explains Bill Kramer, foundation and soils engineer for Illinois DOT. Studies to determine those values are under way. One of the largest IC research projects is TPF-5(128), a three-year, $750,000 pooled fund between Georgia, Indiana, Kansas, Maryland, Minnesota, Mississippi, North Dakota, New York, Pennsylvania, Texas, Virginia and Wisconsin. More details are at www.intelligentcompaction.com.

Artificial Intelligence?

Bomag’s parent company in Germany began instrumenting rollers in 1983 and claims to be the first to have introduced “intelligence” with its first automatic drum-control mechanism more than 10 years ago. It even went so far as to trademark “intelligent compaction” (it has since abandoned ownership of that term) and today offers a growing line of more than one-dozen IC machines. About 500 of them are working globally; 100 are in North America. One place where European contractors are using IC is for building roadbeds for expensive, high-speed railways, Dennison says. In the last decade, more than half a dozen IC brands have emerged, as well as bolt-on, aftermarket indicators for existing rollers.

Another development coming to cohesive-soil rollers is based on how their padded feet penetrate the ground, rather than drum-vibration forces. Caterpillar, for example, is trying to measure the effect of rolling resistance on engine stress. “For material that is not very well compact, it takes a lot more power to move the machine through it,” White explains. “As the material becomes stiffer, it takes less energy to move through the fill.”

Just what is “intelligent,” however, is still debatable. While more than half a dozen brands provide measurement, only two—Bomag and Case (a North American rebadge of Swiss maker Ammann)—automatically...