For new asphalt pavements, smoothness isn’t everything, but it ranks right up there. Studies have shown that smooth pavements not only please the traveling public, they last longer.
So when the National Asphalt Pavement Association (NAPA) gives out its Quality in Construction Awards, the judges consider smoothness as one of the criteria they use in determining the winners. The projects presented here all have at least two things in common: they all won 2009 Quality in Construction Awards from NAPA, and they all used Topcon System 5 electronic grade control systems to control the screeds on their pavers.
Due in large part to electronic screed controls, the contractor achieved excellent asphalt smoothness results in building 16 mi. (25.7 km) of new four-lane highway in Idaho. For the new section of U.S. 95 near Genesee, Poe Asphalt Paving Inc. used a Blaw-Knox 5510 paver equipped with a Topcon tracker that read a stringline on the first leveling lift of asphalt. For most of the second lift and all of the third, Poe ran two Topcon non-contact skis, one suspended from each side of the paver.
Poe used a stringline for the first lift because the paver had to run on a base of cap rock, which consists of large 3-in. (7.6 cm) stones.
“We paved the leveling course — and even part of the intermediate course — using a stringline because the cap rock was prone to some movement under the paver,” said Josh Smith, highway division manager of Poe. “That rock has little or no fines to hold it together. It’s designed for drainage.”
John Cushman, Poe’s equipment manager, said the Topcon System 5 works very well to control the paver screed.
“We’ve had great results with it,” Cushman said. “And our Topcon dealer has provided us with good support. The Topcon System 5 and non-contact ski is the best system available for achieving maximum smoothness.”
Smith said Poe earned a substantial smoothness bonus for its work on U.S. 95. The International Roughness Index numbers ranged around 45, compared to a target of 60 or less — less is better.
No Problems Whatsoever
Using a Topcon System 5 with a non-contact ski to control a Blaw-Knox 3200 asphalt paver helped Orlando Paving Co., Orlando, Fla., achieve award-winning smoothness on a mill-and-fill project in Florida.
Located on SR 528, the project covered 66 lane mi. (106 km) and entailed milling up 3.5 in. (9 cm) of asphalt, then placing two structural lifts back — first a 2-in. (5 cm) lift, then a 1.5-in. (3.8 cm) lift.
“We ran a non-contact ski on one side of the paver and used slope control on the other side where necessary,” said Paul Miller, construction manager for Orlando Paving.
“We love the Topcon system,” said Miller. “We’ve had Topcon for several years and we’ve had no problems with it whatsoever. All of our pavers are equipped with Topcon System 5 controllers and they all use non-contact skis.
The contractor did not use a Roadtec Shuttle Buggy for the two structural lifts, but did so for the 0.75-in. (1.9 cm) open-graded friction course on the surface.
“With the Shuttle Buggy you keep a constant movement, a steady pace and you virtually eliminate segregation,” said Miller.
The results on the surface course were a 4.17 ride number on a laser profiler, with 5.0 being the best possible score.
“The paver moved along at about 30 to 35 feet per minute,” said Miller. “Anything faster would be moving too fast.
“We did a lot of round robin paving, where the trucks would bring out hot mix for paving and pick up milled asphalt to take back to the plant site.”
The contractor produced and laid 160,000 tons (145,150 t) of hot mix asphalt in just 310 days. All paving was done at night on the heavily-traveled roadway, which carried between 45,000 and 90,000 vehicles per day. The contractor worked the project between 8:00 p.m. and 6:00 a.m. on the mainline and 10:00 p.m. to 5:00 a.m. for the ramps. Basically that left six hours in which to pave, due to the time required to mobilize and demobilize traffic control devices and to stripe the pavement at the end of the shift.
Even though it was a high-production operation, safety came first, Miller said. The project was completed, under heavy traffic, with no accidents involving the construction operations.
“On a project like this one, we have a number of safety procedures to plan and set up, and we make sure that we have the discipline to follow them,” said Miller. “We had safety meetings every night before work began and discussed in detail the objectives for success, and made sure that everybody knew the stopping and starting stations every night. At Orlando Paving, safety is our culture and we are dedicated to protecting our personnel as well as the traveling public. Working safely is a matter of good common sense, but you need to have the commitment to use all the right procedures and protocols.”
Smoothness in Georgia
Using electronic grade controls and a material transfer vehicle proved the keys to exceptional smoothness on two stretches of a mill-and-overlay project in Hinesville, Ga.
The Georgia DOT specifies that a milled asphalt surface meet a smoothness requirement of 1,325 mm/km — and the finished pavement must meet a spec of 1,025 mm/km.
“So we used our electronic grade controls on the milling machines,” said Robert Royal, area manager for APAC-Southeast in Savannah.
The project was 4.734 mi. (7.6 km) long, and APAC used two milling machines — one equipped with a Topcon System 5 and the other with a non-Topcon electronic grade control system. Milling depth was 1.5 in. (3.8 cm), and APAC replaced that with 1.5 in. of new hot mix asphalt.
For the paving, APAC used a Roadtec paver equipped with a Topcon System 5 electronic grade control.
“It’s a four-head sensor system with non-contact skis suspended from each side of the paver,” Royal said.
The APAC paving crew improved the ride of the old pavement by 46 percent.
“I’ve worked with the Topcon screed controller and with other models,” said Elmer Baggett, APAC/Southeast equipment manager. “I prefer the Topcon over anything else by far, because it’s more durable. As long as you set it up properly, the Topcon System 5 does great.”
“Smoothness of milling is all about continuity and truck management. We operated the milling machines at a pretty slow travel speed, to permit more revolutions per minute of the cutter. Plus we wanted to flow the trucks smoothly to and from the mill’s conveyor belt. With paving, you want to minimize stops of the paver, and that’s what the Shuttle Buggy will do. By serving as a transfer vehicle, it helps maintain continuity of the entire paving operation,” Royal said.
All milling and paving was done at night, under traffic.
“We have a dedicated traffic control crew that pre-places our maintenance-of-traffic [MOT] devices,” said Royal. “They ride the lane closures and move the MOT devices as needed to make sure we follow the state specs.
“We ran between 18 and 22 trucks on mainline pulls,” Royal said. The trucks hauled asphalt 36 mi. (58 km) from the plant in Savannah to the site in Hinesville. “We had excellent project management to coordinate between the roadway and the plant,” Royal said.
James D. (Darrell) Cannon was the project manager; Joe Hires was the quality control manager. Jeff Andrews was the operations manager and Elmer Baggett “was a tremendous help in making sure that all of the paving equipment and corresponding electronics were set up properly and in good working order,” Royal said.
Today's top stories