US Highway 71, Clay County, IA
Contractor: Cedar Valley Corp., LLC
Owner/Engineer: Iowa Department of Transportation

US Highway 71 is a major north-south artery that intersects east-west US Highway 20. The highway was originally paved with 7 in. concrete in 1931. Over the years, the roadway received numerous asphalt overlays, and in some places, it had deteriorated so badly that full depth asphalt repairs had been performed.

The highway was plagued with thermal cracks, failing joints, severe joint roll-down, and bottom-up cracking. The contractor, Cedar Valley Corp. performed the work on this 6.88 mi. project, which called for milling the existing highway and placing a 124,000 SY of nominal 6 in. unbonded concrete overlay.

During the design process, the Iowa DOT determined that different saw cut patterns were necessary over the full-depth asphalt compared to the pattern called out for over the composite sections. The DOT specified sawing the concrete overlay on top of the full depth asphalt sections in 6 ft. x 6 ft. panels. Therefore, five longitudinal saw cuts and crosscuts on 6 ft centers were made on the 32 ft wide pavement in the full-depth asphalt sections.

The composite sections, which made up about 47 percent of the project, were treated differently. The sawing pattern for those sections created 8 ft x 9 ft panels. The composite sections required three longitudinal saw cuts and crosscuts on 8 ft centers. On a typical paving day more than 35,000 lineal feet of sawing was required. The entire project required a total of 305,700 lineal ft of sawing.

To transition between the full-depth asphalt sections and the composite sections, the DOT specified that 15 lineal feet of 16 in. concrete was to be placed on the 32 ft wide pavement. The project contained five of these transition sections. The plan did not address how to transition successfully between the two different saw cut patterns, which did not line up. The plan also did not address how local traffic and haul traffic would be able to pass through the full-depth asphalt pavement removal areas during construction.

CVC proposed a mutually beneficial solution that was accepted by the owner. The joint at each edge of the five transitional 15 lineal foot, full depth sections was sawed full-depth transversely to stop the longitudinal saw joints from propagating across the panel.

Another problem was how to maintain local access and haul concrete through these transitional areas. To address the problem, the contractor recommended filling half the pavement transition area with rock and haul material. Then after reaching the transition area, the paving crew stopped long enough to allow a fine-grade crew to remove the rock and fine-grade the transition panel to the correct 10-in. depth.

The transition areas presented their own set of challenge, including the paving thickness, which abruptly changed from 6 in. to 16 in. The contractor was concerned about smoothness, and the likelihood of creating either a bump or a dip. To solve the problem, CVC paved the 10 inches by hand, with the help of a material placement/transfer machine, to bring the transition panel up to the existing elevation. This allowed the contractor to pave the remaining 6 in. with the paver while the 10 in. of concrete was still plastic.

The DOT assigned 116 working/calendar days to this project. Cedar Valley started the project on June 17, and completed the entire project by October 28, earning $118,500 in time incentive pay.

The varying depths, transitions, and other factors had the potential to impact Cedar Valley’s ability to attain the maximize pavement smoothness incentive. However, excellent pre-planning and execution enabled the contractor to achieve excellent smoothness. In fact, the contractor earned 83.3% of the maximum zero band smoothness incentive on the mainline paving, earning a $95,500.