How to Pave Highways on Hills

Norris Asphalt Paving Co shares how it won the top industry award with Iowa’s US34 project—over hill and dale

Merrill G. Norris founded what is now Norris Asphalt Paving Company (N.A.P.Co.) in 1947 and the company has been paving Iowa ever since. The company purchased a portable 300 ton per hour (TPH) Barber-Greene drum mix plant in 1983 that featured one of the early computer-controlled blending systems. In 1984, they set up their first permanent asphalt plant—a 5-ton Cedarapids batch plant—on Black Hawk Road in Ottumwa. By 2005, the company’s asphalt division was ready for an upgrade. It purchased a new 400 TPH Astec double drum plant with complete computer control, variable frequency drive motors and the unique drum where mixing takes place in the outer shell outside the drying drum.

N.A.P.Co. includes a team of four asphalt plants that sell HMA products from mid-April through mid-November and three paving crews placing approximately 400,000 tons of hot-mix asphalt (HMA) each year. For the 2014 paving season, 79,000 of those tons were allocated to the Iowa Department of Transportation District 4 project on U.S. 34. Those tons turned out so smoothly that the crew achieved its second ever Sheldon G. Hayes award from the National Asphalt Pavement Association (NAPA). N.A.P.Co. President Brady Meldrem and others shared some insights as to what it takes to pave an award-winning pavement—particularly one with the hills and an average 25-mile material haul from the plant that the U.S. 34 project had in Adams and Montgomery counties.

NAPA reported that the 15-mile project dealt with variable widths, numerous turning and climbing lanes, and long material hauls. The project also included widening the road, including an almost 2-mile section of roadway that went from two lanes to four lanes, and then back down to two lanes. In addition, another Iowa highway—U.S. 71—intersected the middle of the four-lane portion.

“I don’t think there was a flat spot on this project,” Meldrem said. “I think there were passing lanes going up every hill.” He shared that approximately 40 percent of the overall length of the project had climbing lanes.

To mill and pave steep grades, a crew can make the job easier by pointing the machines in the right direction. While the N.A.P.Co. crew used a tracked Roadtec 195 paver, the use of a tracked machine versus a wheeled machine is not as vital to success on hills as the crew’s use of best practices, according to industry consultants. Slow and steady still wins the race.

Long-time paving superintendent for the industry, Ray Eisner of Denver, Colorado, shared the tip that a crew will have better control of the head of material and consistent mat depth when paving uphill than when paving downhill. Eisner suggested project managers plan passes so that the paver can pull uphill whenever possible, but it’s not the end of the world to pave downhill. The crew merely has to pay attention to the details and best practices. Tracking details and quality is something Bob Mobley’s crew is efficient at doing. Mobley is the paving superintendent for N.A.P.Co., and has every reason to be proud of his team.

To start, the team milled 0.5 to 1 inch of the existing east side of the roadway, Mobley shared. “It was widened 4 feet on each side, even in the four-lane section,” Mobley said. “What was difficult in the four-lane section was going from two lanes to four lanes in such a short area.”

The four-lane section was 1.8 miles long, and sitting in the middle of this was the U.S. 71 interchange with ramps.

“When you talk about varying widths, that’s extremely difficult to do,” Meldrem said. “It’s not just ‘put the paver down and measure.’ The lanes go from side to side, and Bob Mobley and the whole team did a great job of getting it all laid down.”

A spokesman for IDOT said the company’s experienced personnel were a valuable asset to this project.

“The U.S. 34 project was fairly complex in the fact that it contained nine climbing lanes, five bridges to transition into, two major intersections with turn lanes and variable widths, as well as transitions into and out of a 2-mile long, four-lane section with a major interchange,” Scott Nixon, IDOT’s resident construction engineer, said.

Placing the mix on climbing lanes is only half the battle. N.A.P.Co. succeeded in achieving the state’s required density on joints and mainline, which resulted in a smooth surface. Meldrem shared that the project received 89% of the available smoothness incentive.

Ray Brown, National Center for Asphalt Technology (NCAT) emeritus director and the independent consultant who inspected each project in the awards competition, said the pavement performed well in every single category to win the top award. “At the time of inspection, the completed surface was very smooth and dense without any cracking, rutting, raveling or segregation,” Brown said.

The way to achieve excellent compaction includes best practices, of course. Eisner spoke to the specific technique to use when rolling on a steep grade.

“Rolling is the part that gets tricky,” Eisner said. “You can stretch the mat if you’re not careful. The key is to only vibrate going up the hill. You don’t want to shove that wave in front of the lead drum.”

In other words, even if the paver is placing the mat downhill, the roller operators can adjust their patterns so that they only operate in vibratory mode on the uphill direction of their passes.

The end result for N.A.P.Co. was a superb driving surface for the motorists in Iowa that garnered the company the 2015 Sheldon G. Hayes award. At the awards breakfast in early 2016 where Meldrem and other officers from the company accepted the award, Meldrem credited his workers—everyone from the paving crew to mix designers, logistics and quality control—for the win. “The fact we’re getting recognized makes us feel like we’ve won the Super Bowl,” he told the audience. “I’m very lucky to have people that put so much attention into quality.”