Hot Project

Time, Mix Temperatures Make Bridge Paving a Challenge

Moisture is a constant companion, and threat, to the Hamilton Fish Newburgh-Beacon Bridge. Moisture penetration and its freeze-thaw cycle had begun to damage the concrete surface of the bridge that carries Interstate 84 across the Hudson River in New York. That led New York Bridge Authority officials to take action that was in the public interest—but certainly a challenge for the contractor.

First, the bridge had to be resurfaced in sections, with only 11-hour night-time closings allowed. That meant milling, cleaning and paving each portion in a single shift.

Second, the mix contained a high rubber content, which required extremely high temperatures.

“It was a fairly difficult mix to work with, but the most pressure came from moving equipment on and off the bridge deck to mill, clean, dry and pave,” said Alfie Bockemuhl, PE project manager with Argenio Bros., Inc. “There was a $10,000 per day fine if we didn’t get off the road early enough. And there were worries about having to stop in the middle of a shift. We were constantly watching the weather.”

The Challenges

The 304 m (1,000') twin-span, cantilever bridge, connecting Newburgh and Beacon and only a few miles from the United States Military Academy at West Point, was last overhauled in the early 1980s. This year, Authority officials determined the best course was to repair the concrete surface and any underlying damaged portions of the span, then place a lift of asphalt with high rubber content to seal the concrete and prevent future moisture penetration.

The work started in September and continued through much of October. The specs called for milling 38 mm (1.5") of concrete, then cleaning the area, and then placing 38 mm (1.5") of the rubber-based asphalt.

All work on the three-lane bridge took place at night. Crews were allowed to close one lane at 7 p.m. and the second lane at 9 p.m. That left one lane open at all times. Sections of the road were milled and paved in a single night. Crews had to be off the road by 6 a.m.

The lanes are 3.7 m (12') wide, with 457 mm (18") outer shoulders. The crown is in the middle of the center lane, with a 2 percent cross-slope running off it.

“The bridge had a very consistent deck surface, so we just mimicked it,” said Bockemuhl. “We just made sure we kept the same grade when we milled, and followed that when we paved.”

There was no rideability spec per se, “but we did have to maintain a high degree of rideability,” Bockemuhl said.

Shoulders were not milled or re-paved. “There is a catch basin every 100' (30 m), and it would have added considerable time and money to the project,” Bockemuhl said. “The Bridge Authority chose not to include any shoulder work.”

Milling

Repairs were made before milling even started. Obvious troublespots were jackhammered and filled with a quick-drying concrete.

A Cat® PM200 Cold Planer then made a pass at a width of 2.2 m (88"). It took the mill two full passes, and one half pass, to complete the work.

Milling also exposed more damaged areas. Argenio Bros. crews chipped out the trouble spots and applied fast-patch, which dried within 20 minutes. This created complications because the repairs had to go quickly, as the cleanup—and then paving—still had to follow, and all work had to be completed to meet the 6 a.m. daily deadline.

This portion of the project proved to be a real challenge for the crew. Original estimates were that 23 m2 (250 ft2) of the surface would need the fast-patch. More than four times that amount ultimately was required.

Cleaning and Drying

Bridge authorities were determined to make the resurfacing last. Part of that effort hinged on exhaustive cleaning that would ensure adhesion of the sealant, and then the asphalt.

The first step after milling was a traditional sweep to remove heavy dust. Next came a high-pressure wash and another sweeping. The slurry was vacuumed into a truck, as the materials could not be allowed to fall into the Hudson River.

The power wash created moisture, so a jet dryer blow-dried the deck until the concrete moisture content was below 6 percent. The dryer worked at a temperature of about 149˚ C (300˚ F), hot enough to expedite drying without damaging the bridge.

An edge sealer was applied and a proprietary tack, which prevents pickup of the rubber-based asphalt, was placed in the main areas of the cleaned surface.

“The cleaning process was very time consuming,” Bockemuhl said. “As a result, we were covering roughly one-tenth of what we normally could do in the same timeframe.

“The cleaning also created that many more moving parts on the jobsite. You take the traditional mill and fill out of it, and now you have to make sure the washers all function, that the vacuum truck does what it has to do, that the equipment that dries the deck is ready to go.”

The timing meant many of the pieces worked simultaneously. “We didn’t have the luxury of completing 100 percent of one step before starting another,” Bockemuhl said. “There just wasn’t time.”

Besides logistical challenges, it made for jobsite congestion. “Including drivers and subs, we had 30 people on the deck at all times,” Bockemuhl said. There was not much room for maneuvering since one of the three lanes remained open to traffic, and the shoulders were only 457 mm (18") wide.

“Traffic is always an issue, and that was certainly the case on this job—on a bridge,” Bockemuhl said.

Paving

The paving process had its own challenges. The mix required very high temperatures to liquefy the rubber. The asphalt left the plant at a temperature of 238˚-243˚ C (460˚-470˚ F) and arrived at the jobsite at about 232˚ C (450˚ F). It was 177˚ C (350˚ F) behind the paver. Crews were actually off the asphalt at a temperature of 121˚ C (250˚ F).

A Cat AP1055D Asphalt Paver with an AS2301 Screed placed the 38 mm (1.5") lift at a pace of about 4.6 m (15') per minute, at a typical width of 5.6 m (18.5'). “The overall job was about doing every step right, and not trying to hit a production number,” Bockemuhl said.

The paver’s automated grade and slope settings helped it match the milled surface.

The operator still had much to watch. “Every 100' (30 m) we tied into a bridge joint or a steel finger joint,” Bockemuhl said. “Our approach into and out of those joints was critical in ensuring there were no bumps. There is virtually no flexibility when you’re tying into a piece of steel.”

With the exception of the high temperature, Bockemuhl said the mix was typical in many ways, but problems did result when it cooled. “Once you lose a good hundred degrees (Fahrenheit), the mix becomes difficult to work with,” he said. That meant crews had to be particularly careful when finishing the last section for that day. Crews had to make sure the paver was removed quickly enough and the last of the mix quickly compacted.

The asphalt also proved a challenge in terms of appearance. “Anything you do to that mat creates a blemish,” Bockemuhl said. “If you were to walk on it, you’d never get the footprint out. It reacts differently.”

Compaction

Only a breakdown and finishing roller were required. Handling breakdown was a 3.6 metric ton (4 ton) roller. It went to work immediately behind the paver; the mix was close to 177˚ C (350˚ F) at first contact. The high temperature was the reason for the lightweight roller.

That roller made a pass up, a pass back, and then moved on. A Cat CB54 Tandem Vibratory Roller handled finish rolling, with two static passes. Testing showed that these patterns produced a little more than 94 percent of theoretical maximum density.

Finishing Touches

Bockemuhl looks at the successful completion of the project as more a mastery of logistics than the paving process. “It was all the moving parts, and also finding creative ways to complete the sweeping and cleaning—and drying,” he said.

The project serves as a reminder that a paving project is about the successful completion of every step, not just how many tons are placed in a day.

Pullquote: “It was a fairly difficult mix to work with, but the most pressure came from moving equipment on and off the bridge deck to mill, clean, dry and pave.”

– Alfie Bockemuhl
Argenio Bros., Inc.

Sidebar 1:

Lighting up the night

Visibility was a challenge on the Hamilton Fish Newburgh-Beacon Bridge. The extremely hot mix temperature created more steam than usual. Yet the tight working area created few opportunities for light stands.

The solution: Powermoon® lighting.

Powermoon systems reduce glare and shadows to enhance visibility. They also attach to and move with the machines—a crucial benefit on this jobsite.

“It created good light for all the guys,” said Alfie Bockemuhl, PE project manager. “It was good ambient light. We didn’t have to put 15 light stands out there. It was really nice on a crowded night-time job like this, with the only ‘free’ space an 18" (457 mm) shoulder.

“There simply wasn’t room for all the lights, and we saved time by not having to set up and take down the lights daily. Time was too tight as it was.

“Those lights really did the job.”

 

Sidebar 2:

A Ride to Remember

Sam Lewis has spent much of his career driving trucks. After spending a night behind the wheel of a new Cat® CT660 vocational truck, Lewis was impressed.

“It’s definitely the future,” said Lewis, owner of Speedway Trucking, based in Newburgh, N.Y.

Lewis made multiple trips to and from the Hamilton Fish Newburgh-Beacon Bridge during the restoration project. One night, the local Cat dealer provided Lewis with the new CT660 vocational truck to drive for a shift. “I loved that truck,” he said. “It drove like a car.”

He specifically praised the comfort and visibility of the CT660 and the smooth shifting of the X31 automatic transmission.

The loads were heavy—Lewis hauled millings—but the weight wasn’t an issue. “It has the power and torque,” he said.

The jobsite was tight, but the CT660 is built for maneuverability. The chassis features a set-back axle, class-leading wheel cut and extra-tight turning radius for enhanced maneuvering and driving performance.

“I would tell anyone who is looking, ‘That’s the truck to buy,’” Lewis said.