Cheshire, Connecticut-based Lane Construction is nearly one year into a project in Yadkin County, North Carolina, that will provide a new unbonded concrete overlay surface, wider shoulders and a new guardrail along a 6.5-mile stretch of I-77. Lane Construction teamed up with HDR Engineering on the $59.4-million design-build project, which also includes related ramp work at the U.S. 421 interchange.
Construction began in February 2007 with full depth patching throughout the project in areas where the existing pavement had failed. Lane saw cut and removed those areas, which were replaced in kind with continuously reinforced concrete, according to Jim Seybert, project manager with Lane Construction.
Along with the full-depth patching, a 4-foot sub slab was also constructed to move the highway towards the median. Delta Contracting, Inc. of Haw River, N.C., milled out the existing asphalt shoulder with a Wirtgen 1200 asphalt mill to a depth of 12 inches. Carl Rose & Sons, Elkin, N.C., then placed 4 inches of hot mix asphalt. Lane followed using a Miller 8100 formless paver to place the 4 feet of sub slab.
Curtin Trucking & Drainage, Inc. of Charlotte, N.C., also installed 4-inch sub drain at the edge of the concrete in required areas using a Vermeer trencher. Carl Rose & Sons followed behind Curtin, backfilling the final 4-inch depth of the drain with asphalt and overlaying the shoulders to address some drop-off issues. This process led into the summer when work began on constructing a detour in the median, a traffic management solution that Seybert believes helped the design-build team win the project.
Using the permanent 10-foot asphalt shoulder called for in the specs, Lane chose to provide a permanent 12-foot asphalt median shoulder and then placed an additional 13 feet of asphalt in order to install a temporary road. The project's design allowed for moving the highway towards the median in order to accommodate the additional height of the overlay at certain points and to eliminate potential sliver fills — an environmental concern. Lane used a Caterpillar D5 dozer equipped with a GPS unit to construct the median. Although more of a placement machine, Lane successfully used the dozer to grade as well. In addition they also used a John Deere 872 motorgrader outfitted with GPS and laser augmentation.
"We were pleased to see the condition of the median," says Seybert. "It didn't take much to get a stable foundation for the detour. It worked very well. The 13 feet added to make the detour will be milled out at the end of the project and recycled."
Once the detour was completed, one complication did arise. The asphalt for the detour was placed at the level of the new highway, which is nearly a foot higher than the existing pavement, and this caused drainage problems. In heavy downpours, the water had the potential to pond up against the detour and flow back onto the highway.
"We thought we had installed enough drainage underneath the detour to handle it," says Seybert, "but we got caught a couple of times. This was our biggest challenge as far as (the detour) was concerned."
Work began on the northbound lanes of the project first, and Lane has overlaid 4.5 miles of the project and completed 35 percent of the concrete work to date. This work was accomplished during fall 2007 between Labor Day and Thanksgiving.
Lane is using a Guntert & Zimmermann S850 paver with a Dowel Bar Inserter (DBI) to place the 11 inches of concrete on the mainline. Jim Seybert explains:
"The DBI is a traveling piece behind the paver. A dowel tray sets above the pavement. A person loads the bars (1-3/8 inches in diameter and 18 inches long) into a chain feeder. The bars roll down into place, and drop into each location about a foot apart. When the 15-foot mark is reached, which is the joint spacing required on this job, the DBI stops while the paver keeps moving. A trigger is tripped and the 'fingers' of the DBI vibrate the dowels down into the concrete and into place.
"The fingers then lift up; the DBI catches up to the paver and reloads another set of dowels. A correcting beam carrying a head of concrete oscillates behind the DBI to fill any indentations that are left."
Lane Construction is also using maturity meters to determine the strength of the concrete. Wireless probes are placed in the concrete to check the temperature. Lane performed a lot of preliminary work on the mix designs in order to determine what temperatures correlate to what strength. During the summer, Lane was able to achieve a 450 flex strength in an average of 24 hours to 36 hours.
The project has now moved into cold weather paving, and Lane is using two layers of plastic to maintain required curing temperatures. They expect to place 6,000 cubic yards of concrete by Easter on the southbound section. Lane hopes to have all of the paving work completed by Thanksgiving of this year.
In total there will be 66,000 cubic yards of concrete used on the project, and Lane is using a CMI/Johnson-Ross Unirover 1248 with a 12-yard batcher and a single drum to produce the material.
"We're able to get the batch mix time down to 60 seconds with acceptable results on uniformity tests," Seybert points out.
Once the pavement is placed Lane will diamond grind the entire surface. Often used in conjunction with other concrete pavement rehabilitation techniques, diamond grinding provides a smooth riding surface and enhances surface texture and friction. This reduces road noise and improves safety.
In addition to rehabilitating the mainline road surface, Lane Construction is also adding new pavement on the ramps and loops at U.S. 421, and after Labor Day Lanford Brothers Co., Roanoke, Virginia, will be jacking up the two I-77 bridges that cross over U.S. 421 by approximately 12.5 inches. The increased height of the bridges will allow them to meet the grade of the new unbonded overlay and increase the clearance on U.S. 421.
With traffic counts along this stretch of highway expected to double by 2027 — from 38,280 now to 68,640 — and a deteriorating pavement, the reconstruction of I-77 had become a necessity. By employing a creative traffic management plan and time-saving construction techniques, Lane Construction and HDR Engineering are optimistic that they will beat the June 30, 2009, deadline for completion.