Backing It UP

March 2, 2006

Pittsburgh won on the road long before the Steelers put together four straight white-jersey wins for the Super Bowl XL championship in January.

Pittsburgh won on the road long before the Steelers put together four straight white-jersey wins for the Super Bowl XL championship in January.

Lindy Paving Inc., New Castle, Pa., hit on every play of its game plan for the super pave of 2005, providing 110,000 daily commuters a solid black road leading in and out of the steel city. Work done on 6.1 miles of Parkway West (I-279 North) was deemed worthy of the National Asphalt Pavement Association’s Sheldon G. Hayes Award, which is pinned on the top asphalt-paving job in the country. Highway pavement projects using more than 50,000 tons of hot-mix asphalt (HMA) go through two years of drills and tests in order to qualify for the honor.

“We knew it was a special job just in the shear magnitude of work we had to do,” Dan Ganoe, operations manager for Lindy Paving, told Roads & Bridges. “To be quite honest I don’t think we ever imagined it would be the job of the year, but definitely everyone was very proud when they left that job. It was quite an accomplishment.”

For Lindy Paving, winning came down to strong starters and dependable backups. Because the paving schedule was extremely tight—the contractor had a total of 11 weekends to complete the task; it was completed eight—the Pennsylvania Department of Transportation (PennDOT) specified a line of equipment in reserve in its $7.8 million contract. Lindy Paving needed an extra weekend or two, but never really had to lean on a second string of machinery.

“We have [required backup systems] in the past on major routes where you are doing closures and you have to get it open for rush hour,” Angelo Pampena, assistant construction engineer for Penn-DOT, told Roads & Bridges. “This contract made sure if anything broke down we didn’t want it to become the issue that would stop us. Once we implemented a detour we were taking 110,000 vehicles a day on these other routes through various municipalities and state routes.

“If we get all that set up and there is a breakdown obviously that would cause us some major problems with our customers. That just wasn’t an option.”

Covering any cracks

Premature pavement breakdown was a thorn in PennDOT’s side on this road to Pittsburgh. The state placed asphalt back in 1998, only to see it quickly catch a severe case of raveling and longitudinal and transverse cracking. Since it was one of the initial Superpave projects in the area, the agency found most of the project’s value in the area of education.

“It was considered premature distress as far as the pavement goes by PennDOT,” Joe Conti, quality control manager for Lindy Paving, told Roads & Bridges. “They were experiencing problems with the surface due mostly, they suspect, to permeability.”

PennDOT wanted nothing left to do with the existing pavement, and decided to mill all the way down to the concrete sub-base. It was an all-out reconstruction job located in a high-traffic area with very little room for error. Before the first milling machine sunk its teeth into the decay, Lindy Paving had a thorough plan covering all levels of work in place. All workers knew all the available routes in and out of the area, and to eliminate vehicles at the jobsite the contractor used a shuttle bus to move people. Different weekend events required different sections to be open, making it impossible for Lindy Paving to start at point A and end at Z. The company had to be a precise scavenger, taking what the schedule—and weather—was offering. The project was broken down into three major zones—outbound and inbound.

“We basically gave ourselves six work areas,” said Ganoe. “So weekend one we might had been able to work inbound and weekend two we may had been able to work outbound. We couldn’t even maintain a linear progression throughout the job.”

The tight schedule made watching the weather a religion. Both Lindy Paving and PennDOT followed every possible forecast.

“We were calling Thursday night for Friday night to see if we would pull the plug on the project for the weekend,” said Pampena. “We also adjusted our work based on the windows of opportunity. If we saw there may be some rain coming in on a Saturday morning we would do some milling or bite off a little smaller area to try to get it completed.”

It didn’t take long for the rain to come. The drops hit the first weekend, forcing crews to pull back. To prevent further rain delays, Lindy Paving decided to bring in a portable surface dryer, which was essentially a jet engine on a trailer.

“From that [first weekend] we knew schedules would get even tighter,” said Ganoe. “There were a couple of weekends when it was threatening to rain and we brought the jet out on the jobsite and used it to dry the pavement.”

Changing course

After holding meetings throughout the week, Lindy Paving set the work zone, which was maintained and adjusted based on conditions by a traffic control supervisor, at 10 p.m. on Friday night. Three to five milling machines—a variety of Wirtgen models (DC 2000, DC 2100, DC 2200)—opened the weekend activity grinding down 5 to 9 in. of asphalt. According to Ganoe the average weekend produced 8-10,000 tons of milled material. The clearing usually lasted until 7 the next morning. To prevent another bout of premature cracking, crews armed with Petrotac followed the milling operation. After spraying an adhesive or primer over the longitudinal joint, the Petrotac, which came in a roll, was applied.

The area was now ready for paving. Lindy had two paving lines working the scene. One would handle ramps or acceleration lanes while the other dealt with the mainline. Three asphalt plants—a CMI (400 tons/hour), Standard Havens (300 tons/hour) and Gencor (400 tons/hour), which strategically surrounded the jobsite, produced material at 310°F. Trucks would haul the HMA to two Roadtec Shuttle Buggies, which made the transfer over to a pair of Caterpillar AP-1055D asphalt pavers armed with a 40-ft ski. According to Conti the temperature of the asphalt at the time of laydown was about 295°F. The dual rolling patter consisted of three Sakai high-frequency vibratory rollers. The first two machines operated out of the vibratory mode at 4,000 vpm, while the third stayed in static mode. By late Sunday night the road was back open to the public.

Original plans called for the placement of a 3?4-in., 9.5-mm leveling course followed by a 3-in., 19-mm binder course and a 11?2-in., 9.5-mm wearing course, with a fiberized AC 20 seal on the center joint. Lindy Paving, however, suggested a switch. The contractor thought it would be better to start with the binder course followed by the leveling layer.

“One concern was due to the varied depth that we had out there we felt it was a better structure to add the increased binder capacities as opposed to making that buildup with a wearing course,” said Ganoe. “Once we milled we could go down through and do a binder leveling.”

“That binder is a 19-mm mix so it carries a little more structure than the 9.5-mm leveling course,” added Conti.

PennDOT agreed, and Pampena believed the adjustment ended up saving the operation serious material costs.

“When you are trying to do buildup in certain areas, if you do the [leveling] and then build up you are going to end up putting more binder down,” he said. “If you do it the other way, when you are dialing your cross slope into your binder and then putting your [leveling] on it, you’re able to get that easier with less material because now you’re meeting your grade earlier in the process.”

All three mixes were designed to hold up to 10- to 30-million ESALs and contained a PG 76-22 binder. The contract specified that the best aggregate available (SRLE hardness) had to be used for the job.

Field testing consisted of cores and loose box samples. Each 1,200 tons of material was divided into three sublots, which were tested at PennDOT’s Central Lab Facility. Asphalt content, 200 sieve material and field density were the required pay factor items. Test results indicated 100% payment for all lots.

Lindy Paving had to maintain 4% air voids throughout the entire production and had to hit density readings of 92-97%. Conti said they were right around the air void goal and were hitting 95% density in the binder course and 94% with the wearing.

The process was just as intense when it came to checking smoothness. There, the contractor used a KJ LAW P6400 profilometer with an infrared sensor. The profilometer came right behind the paving operation so any adjustments could be made immediately instead of at the end of the day. Crews also measured every lift that went down.

“As soon as that finish roller is done [the profilometer] is right on his tail so we have numbers,” said Conti. “If those numbers are in line with what we need then we continue. If they’re not, then we start troubleshooting.”

Quality consistency did not flinch for the entire eight weekends. Pampena credited this level of craftsmanship to Lindy Paving’s insistence on having everyone who was involved in material handling at the prep meetings.

“Everything they did was exceptional in just the quality and control of their material,” said Pampena. “They were able to do that better than I have ever seen before. The way they handle their aggregate and load their trucks, they go the extra step.”

In the end, Lindy Paving executed a ride index of 39 in. a mile. Before the project began the old pavement was recording 100 in. a mile.

“I drive it two or three times a week and it is doing very well,” said Pampena. “We are hoping to get another eight to 10 years out of it. It’s the gateway to Pittsburgh. If we lose it 110,000 will have to go in a different direction.”

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