ForConstructionPros.com

Take an 11.1-mile stretch of country road, constructed of concrete and asphalt, which straddles two county jurisdictions, with one favoring concrete and the other asphalt, and you have project that calls for an innovative solution that satisfies both. That pretty much sums up the challenge Norris Asphalt Paving of Ottumwa, IA faced when submitting a bid to rebuild Route N58 in Western Iowa.

As a past Sheldon G. Hayes Award recipient, Norris proved to be up to the challenge and was awarded the $2+ million contract in 2003, completing the final top mat earlier this spring. Putting together a proposal that satisfied the engineering requirements of two different government bodies, Carroll and Greene counties, posed the initial challenge for Norris. The two end sections of the two-lane highway were constructed of Portland concrete, with the center section constructed of full-depth asphalt.

"We were working with one county engineer who was a staunch supporter of concrete and that required some extra work to convince him of the benefits of an asphalt constructed project," says Brady Meldrem, Norris president.

Crushin' concrete

The project called for rubblization of the six-inch Portland concrete cement of the three-mile north and four-mile south sections of the road, and cold in-place milling of the center 12-inch-thick asphalt section. The concrete was removed, crushed and metal rebar removed, and then placed back on the roadbed to create a base for the new road.

Manatt's Inc. of Brooklyn, IA was the subcontractor in charge of crushing the concrete. Jason Spooner, Manatt's project manager, says an Impact Tech Impactor 2000 was used to rubblize the concrete roadbed. Using a John Deere 4955 tractor, the concrete impactor was pulled over the road more than a dozen times to break the concrete into 12-inch or smaller chunks in preparation for the crushing operation. A Caterpillar 235 excavator was used to load the rubblized concrete into Manatt's mobile twin crushing plant, comprised of an Excel 2500 primary crusher and an Excel 1500 secondary crusher mounted on paving tracks. The primary crusher reduced the concrete rubble to three-inch chunks, with the secondary crusher reducing the concrete to 1 1/2-inch particles before placing a windrow of the crushed material back on the roadbed. Magnets inside the crushing units were used to extract rebar from the concrete.