Walsh Construction Co., based in Chicago, has been at work on the Dan Ryan Expressway for the last two years getting perimeter walls in place and paving entrance and exit ramps. In 2006 the company paved six miles of express lanes in each direction, four lanes wide. Walsh had six months to remove and replace the 48 lane-miles, for a total of 400,000 square yards of concrete pavement on the project.
Jobsite logistics were a nightmare. The express lanes are the inside lanes of the expressway, so Walsh was surrounded on both sides by three lanes of traffic carrying 100,000 vehicles per day. Commuter train stations and train tracks crisscross the project. At any one time, there would be more than 100 trucks traveling inside the project area, and just getting concrete to the paving site required careful coordination and timing.
“This is a 100% dump truck job with a central mix plant,” says Rocky Bellis, general superintendent for Walsh's Chicago Heavy Highway Division, which is using Gomaco equipment for the paving. “We're placing concrete with either a placer/spreader or a trimmer/placer. We're running the trimmer/placer up in front because it seems to secure the mat of rebar before the belt placer comes along. The belt placer caps, strikes off, and levels the concrete before the paver hits it.”
Walsh's concrete delivery rate was 400 cubic yards per hour. The trimmer/placer was used to place 150 cubic yards per hour. Following behind it, the belt placer placed the remaining 250 cubic yards per hour.
Crews had to pave under 20 different bridge structures on the project. Clearances underneath the bridges were too low for dump trucks to be able to lift and dump their loads on the belt of the placer/spreader, making maneuverability and a 35-foot-long placing conveyor crucial to getting the concrete into position.
Dump trucks could back up to the bridge structure and dump their loads of concrete into the hopper. The operator then used the long placing belt to get concrete in front of the paver, underneath the bridge. Also, with a hopper full of concrete, the operator could easily maneuver in the tight conditions underneath a bridge to place the concrete exactly where it needed to be.
A two-track paver followed behind the placers slipforming the new lane of expressway 14 inches thick and 24 feet wide. But because the piers are so tight at the 20 different bridges, the paver had to get under in each direction, so it was impossible to run the stringline continuously. As the paver reached each bridge, crews locked the paver in on cross slope, and ran it through. “It slowed us down a bit, but versus the cost of steel forms and trying to hand pour two lanes of CRC, there's no comparison,” Bellis says.
Following behind the paver was a texture/cure machine with a skewed tining option. Illinois requires skewed tining on all of its projects. Walsh's texture/cure machine was specially designed with the tine rake on a gear drive.
— Kelly Krueger is the editor of GOMACO World, where portions of this article first appeared.