For a whole host of reasons, Mike Viehdorfer really likes the stringless control system on his new GOMACO GHP-2800 concrete paver. He works for Manatts Inc., a diversified, family-owned construction company based in Brooklyn, Iowa. For this U.S. Highway 71 project in northwest Iowa, Mike is the project manager and this is his second major stringless paving project.
Typically, a concrete paver is controlled by two stringlines set at precise locations on each side of the lane being paved. 3D machine control, on the other hand, saves contractors considerable time and money because it eliminates all of the detailed survey, manual labor, and associated transportation costs normally spent for a highway or runway—staking of hubs, setting blue-tops, and the labor to set up, maintain, and tear down stringlines. Automated 3D control also eliminates the potential for human error with stringline, and its logistical restrictions around the paver.
THE PROJECT
The $9-million project involves repaving a four-lane divided highway for a 9-mile stretch in Clay and Dickinson Counties. Manatts is placing a 6-inch concrete overlay atop the milled asphalt pavement. In the same single pass, the GOMACO GHP-2800 paver widens the roadway from 24 feet to 34 feet with 8 inches of concrete on each side. On one side, the widening unit is 6-feet wide and it is 4-feet wide on the other.
For this project and others to follow, Manatts’ new GOMACO GHP-2800 concrete paver is fitted with a PaveSmart 3D stringless control system from Leica Geosystems. “In the old days, when we were paving on stringline, if you got 50 percent of the available smoothness incentive payments on a project, that was good,” says Viehdorfer. “Now with our Leica system, we expect to earn 70 to 80 percent of the smoothness incentives on any given project.”
And on Highway 71 in August 2011, the Manatts crew was bettering that—earning maximum incentive on about 95 percent of the pavement placed. Naturally, Viehdorfer gives a great deal of the credit for smoothness to the quality of the GOMACO GHP-2800 paver and the experience of the crew. Manatts is running the Profile Index (PI) system for measuring smoothness, which is comparable to, but different from, the International Roughness Index (IRI).
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TRUTH IN NUMBERS
Check out these numbers. The Iowa Department of Transportation says it takes a PI of less than 22 inches of deviation per mile from a zero blanking band to earn the maximum smoothness incentive. On Highway 71, Manatts has been consistently running between 13 and 19 inches of deviation. “Now that we are running stringless, we expect more and we are getting more,” says Viehdorfer.
Production is running well on Highway 71. “We did 4,300 cubic yards of concrete in 12.5 hours,” says Viehdorfer. “We can move right along on an overlay. We are averaging a little over 300 yards per hour, or about 330 yards per hour.”
As the dump trucks deposit concrete on the milled asphalt, the GOMACO GHP-2800 paver spreads concrete and forms it to the full 34-foot width of the new pavement. With the Leica PaveSmart 3D system, Manatts uses four robotic total stations—with two of them active at any time—to control steering and grade on the paver.
BENEFICIAL PARTNERSHIP
Tim Tometich, machine control manager for Manatts, says his company benefits from the GOMACO-Leica combination. “The value that we have is that GOMACO has built their computer to talk to the Leica PaveSmart 3D computer. The GOMACO computer was built with Leica’s stringless technology in mind, and the two computers talk really well to each other.
We asked Manatts’ Viehdorfer why he likes the stringless system. “I love the ease of access to the project,” he says. “You don’t have strings that people were stepping on and tripping over, or bumping into. I think one of the greatest benefits is that we get smoother pavements. When you can do cross sections every 5 feet on a vertical curve compared to 25 feet with stringline, you just end up with smoother pavement. And you get finer yield control.” ■
About The Author:
Daniel C. Brown is the owner of TechniComm, a communications business specializing in construction and engineering topics.
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Modern Contractor Solutions, March 2013
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