Applications and Innovations: A Road from the Past; A Road for the Future
| October 01, 2009 |
This Central Avenue has a prominent past. Granite blocks made up the original roadway built in the 1600s. It came from from small cut blocks used as ballasts in ships sailing up the Hudson River from the Netherlands and other parts of Europe. The road later became the farm-to-market road between Albany and Schenectady.
Later, the street had one of the earliest trolley lines, and with the advent of steam engines, had one of the country’s first passenger railroad lines constructed in 1830 along the Central Avenue corridor between those same cities.
An uptown thoroughfare
This main street has not diminished as an important thoroughfare. But with more 30,000 cars using the road daily, the severely distressed road needed to be resurfaced. The scope of the project includes the rehabilitation of the roadway pavement with milling and overlay, box widening the street, replacement of all curbs and sidewalks, improving the storm drainage system, and the upgrade and/or replacement of existing safety features along the corridor.
Within this stretch of road, Hudson River Construction Co. Inc. used a Volvo PF-6160 paver to resurface and box widen nearly two miles of the road by two feet more on each side, making it more than 60-feet wide with five travel lanes and numerous turning sections.
The roadway was milled down to just above the granite blocks and then resurfaced in two lifts after a truing and leveling course to adjust for profile and cross-slope corrections.
A geogrid fabric on the binder course was added to alleviate any future reflective cracking or possible tensile-strength degradation from the stone blocks, and/or parts of the underlying foundation of concrete pavement, which were still relatively sound.
Michael Hurtt, P.E., design project manager for Colonie, N.Y.-based Clough Harbour and Associates LLP was confident about the general condition of the underlying foundation pavement, but was concerned that with the numerous utility cuts in this foundation, reflective cracking would eventually migrate up through the asphalt surface courses. “We also wanted to bridge the interface between the existing and box widened pavement,” Hurtt says.
The sequence of construction made it necessary to install the reinforcement layer directly below the asphalt top course, Hurtt explains. “I would have liked to have been a little deeper in the pavement section, to have the reinforcement layer closer to where the cracks could begin,” he adds, “but that was not practical based on the requirements of how we sequenced the construction of the box widening.”
The $15 million contract (including extensions) began in the spring of 2007 and the project has just been completed. Outer road rehabilitation and the widened section meant putting in a full-depth reconstruction. Use of a road widener for select backfill to install and replace the utilities, storm drainage, and sewer lines to bring the road up to current standards, has kept construction moving smoothly, Hurtt notes. An 8-foot-wide, 12-inch-deep type-2 sub-base was laid for the under-drain by using the road widener. A binder also was put in with the road widener to match the existing binder that wasn’t removed while establishing the new 2 percent slope.
When it came time to put in 8 inches of asphalt base on the newly widened short sections, Hudson River’s used its Blaw-Knox PF-4410 with an 8-foot-wide screed to put down two lifts. But, it was the Volvo PF-6160 that put down the mainline asphalt 18 feet down to 12-foot-wide pulls, 2 inches of hot-mix asphalt (HMA) binder course and a final 1.5 inches of HMA top course, with a reinforced geogrid between the lifts.
Heavy traffic and shopping center congestion during the day, made night paving the best option for this job. Starting at 7 p.m., traffic delineation cones and signs were installed, along with temporary ramp removals and the new transversal joint sawed where paving ended the night before. Just before tack coating the area to be paved, a street sweeper was used to clean any foreign debris from the surface.
The project began at the west city line and extended into the city. Once the street was cleaned, and tack coated, over the binder lift, a loader/backhoe equipped with a special attachment, secured the roll of geogrid Hatelit C 40/17, and rolled it out where the blocks and concrete were under the road. It would not be placed in the new reconstructed area. Nails would be spaced conveniently for secure attachment in case a truck backing up to the paver might turn its wheels or twist the truck in a way as to dramatically reposition the material.
By 9 p.m., the first asphalt trucks started dumping the 20-percent-recycled 19-millimeter Superpave binder mix, or the 15-percent-recycled 12.5-millimter Superpave surface mix (64 to 22 grade) into the Volvo PF-6160 hopper. A total of 30,000 tons was put down as surface, binder, driveway, and 37.2-millimeter asphalt mix. Because of the short paving duration on the top course, only 900 to 1,000 tons was placed a night. About eight trucks were used to haul the material 15 minutes from the plant when traffic was light. The trucks, some leased, were from 32-ton flow-boy trailers, to 22-ton tandems.
Near the end of the paving project season in 2008, weather temperatures were monitored closely. Ground temperatures had to be at least 45 degrees. When the colder weather came in, the asphalt coming from the plant usually was hotter at about 325 degrees Fahrenheit to allow for the quick cool down cycle. Common procedure was to test behind the second vibratory roller when the temperature was about 280 degrees. Density had to be between 94 to 98 percent with 96 percent targeted with the nuclear density gauge.
The original grade and slope were changed during the milling operation to a 2 percent cross slope for better drainage. The paving with the PF-6160 used the paver’s Blaw-Kontrol II to keep the same slope. On the outside slow lanes, the newly installed curb was used for reference. When the fast lane and half of the center “suicide” lane was laid, 18-foot wide as one pass, the same grade and slope was held while using the non-contact Blaw-Knox Ultra-Eye 5. The newly laid mat was its reference point. A contact ski that the crew had used for years could not be used when the geogrid fabric was down, for fear of entanglement between the two.
Gene Hallock , president of Hudson River Construction Co., says he believes the paver used for the job has the best extensions on the market. “It’s well built, and I like the extension in front of the basic screed for our municipal type of work,” he says. “The augers move in or reverse, and the tunnel extension moves in and out when needed to perform a better material flow.”