Behind the resurfacing of an Iowa highway

Updated Jan 31, 2015

A&I_Dec.-2014_DSC01639When looking up miscellaneous statistics, you learn that average life of a U.S. currency $10 bill is 4.2 years, and a common goldfish – properly cared for – will last 7 to 14 years before going belly up.

When it comes to roadbuilding, the Iowa Department of Transportation expects to see a highway road surface last 20 years. That’s one of the reasons why the Iowa DOT let the contract for a 16.037-mile road-resurfacing project for Iowa Highway 92 between Winterset and Greenfield, Iowa. The approximate 25 miles between the two cities sees an average 1,365 cars travel that highway road surface daily. The highway was last worked on in 1994.

Norris Asphalt Paving Co., Ottumwa, Iowa, was selected for the asphalt-paving portion of the project. The company is a Sheldon G. Hayes Award-winning paving contractor. The Sheldon G. Hayes Award is considered among the most prestigious paving awards in the asphalt industry and is granted after a two-year detailed evaluation of the workmanship of the subject roadway project.

Norris Asphalt Paving has about 75 employees and on the Iowa Highway 92 project an 11-person crew was assigned. The six-week project began at the end of May 2014. The company was responsible for the paving portion of the highway rehab. The stretch of Iowa Highway 92 is 28 feet wide – two 14-foot lanes. Plus, the highway was widened 2 feet on each side.


Milling, roadbed prep

The milling and roadbed prep work was subcontracted by Norris to other contractors. A 4.6-mile stretch on the East end of the project posed a challenge because it had a concrete underlayment. For their contractor to mill the on-average 4.5-inch depth, Norris Asphalt had to close the stretch to traffic for 17 days.

“The rest of the highway project was milled cold-in-place with traffic flow maintained throughout construction,” says Bob Mobley, paving superintendent with Norris Asphalt Paving Co. “The milled asphalt was recycled – we used 20-percent RAP in our HMA [hot-mix asphalt] mix.”

For the highway project, Norris Asphalt laid 12,230 tons of HMA for the base lift and 24,840 tons of asphalt was placed for the intermediate and surface layers. An additional 7,500 tons of HMA was used for the widened roadway shoulders.

On the project, Norris Asphalt used paving asphalt PG 58-28 – a Performance Graded (PG) asphalt derived from selected crude oils via a carefully controlled refining process. The 58-28 refers to a Celsius temperature range: 58C or 136.4F to -28C or -18F.

“Our paving on this project went quite well,” Mobley said. “We were using a new machine – a Roadtec RP-195e, which is a powerful, rubber-track paver made for highway work.”

Norris Asphalt received delivery of the new paver in time to use on the Iowa Highway 92 project.

“Roadtec guys showed up to train us on our RP-195e and after a few minutes we basically said, ‘Not to be rude, but get out of our way … we have work to be done,’” Mobley says. “The machine is easy to learn and operate.”

Mobley says he likes the way the paver steers with its joystick steering and prefers the heavy 40-foot drag screed to no-contact screeds he’s seen on other machines. He mentioned that the dual operator stations can move out beyond the sides of the machine to give the operator a clear view down the sides of the paver. And he likes that the machine is a tread paver.

“Unlike wheel pavers, we get stability even when laying down asphalt on three-inches of choke stone,” Mobley notes. “We get more uniform results with a track paver and there’s a smoother ride as a machine operator. The RP-195e has exceptional rideability.”

Norris Asphalt Paving owns a 2004 Roadtec RP-195 asphalt paver, which probably helps explain the crew’s immediate comfort with the new paver.

“Although the new paver has some great features our older model doesn’t, but I will never give up the 2004 RP-195,” Mobley says. “We’ve paved some incredible roads with it – two of which ended up in the top five for the Sheldon G. Hayes Award; it hits all the critical factors for quality paving results. I can see already that our new Roadtec paver will perform as well.”


Project highlights 

As Norris Asphalt comes to the end of the Iowa Highway 92 project, Mobley identified a few things about the project he’ll remember most.

“This was our first time using the RP-195e asphalt paver and the machine helped us get done quickly and with the quality results we wanted,” he says.

The new paver was delivered from the factory all set up without a need for any adjustments.

The machine, which came equipped with the Guardian Telematics System, proved to be useful with staying on track. Mobley says his team starts out with a very early workday. One morning, the machine started up and idled, but wouldn’t rev up. “I called, not expecting anyone to be available that early, and got through to support immediately,” Mobley says. “I explained what was happening. They said: ‘Let us get into your machine on our end and see what the problem is.’ They called back in 20 minutes and said, ‘Fixed.’”

The 16-plus-mile stretch of Iowa Highway 92 is but one chunk of the 275-mile state highway that runs from east to west across the state. The work that Norris Asphalt Paving Co. performed on the project was subject to the Iowa DOT’s Quality Management – Asphalt (QM-A) program, which holds the contractor responsible for mix design, sampling, testing and making mix adjustments if necessary. In other words, contractors assumed start-to-finish responsibility for the product they produce and place.

Norris Asphalt’s finished road passed all of the I-DOT random density core tests, which check for voids. The finished asphalt paved surface achieved impressive profilograph-measured 12.61 to 12.9 International Roughness Index (IRI) scores.

When asked how they were able to achieve, what many would consider, exceptional IRI scores on the finished paved surface, Mobley said: “Superb paving machine and darn good crew!”

For the I-DOT officials signing off on the work, there is a confidence that the highway section is good to go for at least a 20-year life.

This article was contributed by Roadtec and the Iowa Department of Transportation.