I-76 Fort Morgan to Brush, CO

Project Focus
This $8.2 million CDOT reconstruction of 3.39 miles of I-76 between Fort Morgan and Brush included placing over 140,000 square yards of 10” and 12” thick PCCP with removal and replacement of an existing Concrete Box Culvert, a new inline bridge, multiple box culvert extensions, an MSE wall, embankment, fencing, guardrail, striping and landscaping. The project was built in two phases, using temporary detours at the project ends to move traffic to the opposite lane, and dividing the head-to-head traffic with concrete barriers through the detours and with tubular markers for the length of the project. Traveled lanes were constructed with doweled contraction joints spaced at 15 feet. The pavement surface was textured with a burlap drag and tined longitudinally to provide a quiet and safe surface. Prior to the full-width 38’ wide, minimum 10” PCCP overlay of the mainline, the existing bituminous shoulders were reclaimed with a pulverizing mixer and graded to match the elevation of the bond-breaker and the cross-slope of the new top of pavement. The bondbreaker was a recent asphalt overlay, a CDOT strategy to provide short-term serviceability as an interim step to providing a life-cycle cost effective concrete overlay. Approximately 15,000 square yards of removal and replacement of the existing pavement with 12” PCCP on 6” of aggregate base was required to meet the existing pavement elevation at the project limits and bridge ends.

Project Details
Schedule & Complexity
Two weeks prior to the scheduled traffic switch, CDOT found it was necessary to re-design the bridge and asked the Contractor to “design-build” the changes. By quickly executing the design change and executing a value engineering change to overlay rather than remove and replace pavement for a significant portion of the project, the Contractor was able to keep the schedule intact.

Construction & Innovation
While this project was designed by CDOT primarily as an unbonded concrete overlay, some areas of major super-elevation correction were specified as remove and replace to eliminate what was deemed excessive pavement thickness on the high side at the edge of shoulder. CDOT accepted a Contractor proposed value-engineering alternative to overlay these areas, saving cost and time. This required the PCCP to be slipformed at variable thickness from 10” to 26”. Special care was taken to consider the depth of green-cut transverse saw cut to assure that the shrinkage cracking was controlled. The Contractor mixed concrete on-site using a Rex central mix concrete plant, placing with a Guntert-Zimmerman GZ-1500 paver equipped with an automatic transverse dowel bar inserter (DBI). To maintain thickness tolerances on the PCCP and to correct any haul road damage, final trimming and rolling of the aggregate base was accomplished just prior to the paving.

The Contractor was able to manufacture the structural backfill material on the jobsite from the existing subgrade material. Hauling of larger concrete loads in semi-end dumps resulted in both cost and time savings to the project

Quality
The Contractor's Quality Control Program, partnered with CDOT, provided process control testing and inspections by ACI-certified lab technicians and employees. This was important in building a quality project. While 54% of the incentive for ride quality was achieved, notable because of the difficult paver set-up required by the super-elevation correction, the thickness and strength incentives earned were in excess of 100%. The resulting average total quality incentive earned was 96% of contract's available total.

Close communication between concrete production, trucking and placement crews resulted in smooth pavement with minimal grinds. The Federal Highway Administration conducted MIT Scans for dowel bar placement and concrete quality.

Public Relations
Safe operations for through traffic were provided throughout the project using detour signing, slowed speeds and traffic control devices. CDOT and the Contractor used newspapers and specific project fliers to give public notices of project status and detour changes.