Paving I-195 "Popcorn" At Night
A four-mile stretch of Interstate I-195 in Fall River, Mass., was "popcorned" under the lights by P.J. Keating Co., a division of Oldcastle, on a fast-paced Quality Assurance contract with the Massachusetts Highway Department (MassHighway).
Working between 8 p.m. and 5 a.m. four days a week, Keating installed about 8,000 tons of a 1-inch overlay of latex-modified open-graded friction asphalt hot-mix wearing course — often referred to as popcorn because of its textural similarity to the popular snack. The overlay capped a 2-inch layer of dense binder mix — about 24,000 tons of material — included in the MassHighway contract.
The contractor began work in August 2006 on the resurfacing project, which calls for resurfacing three travel lanes of both east- and west-bound barrels of the interstate plus several ramps and interchanges with Route 24. Last year, Keating milled off 2 inches of existing pavement using a Roadtec milling machine, then laid the 2-inch course of dense binder mix. This year, the contractor completed the work with the 1-inch open-graded wearing course. The job was essentially finished as of August 2007, according to Larry Andrews, Keating's quality assurance supervisor.
Andrews' role requires him to make sure the hot mix meets the state's job specifications. He said Keating is responsible for cutting core samples and testing them, while the state also takes cores — one for every four the contractor takes. He pointed out that under Quality Assurance rules governing asphalt pavements, Keating must meet criteria for ride quality, compaction, plant air voids, asphalt content, and compacted thickness.
The I-195 resurfacing project was a high-production effort on the part of crews led by Joseph Cimini, Keating's project manager. The company employed a CAT AP-1055D paving machine with 12-foot to 16-foot paving width, to lay both dense binder and open-graded mix over the 50-foot roadway. To achieve a fast-moving, smooth operation, the crews used a Roadtec SB 2500 Shuttle Buggy 25-ton-capacity transfer vehicle in conjunction with the paver. Eighteen haul trucks constantly fed hot mix to the Buggy, which in turn kept the paver loaded and running continuously to preclude delays and "bumps" from trucks that would be reflected in the pavement.
A fleet of Hypac rollers performed compaction — two C784 steel drum vibratory machines, a C766 steel drum vibratory and a rubber-tired compactor.
Keating's Acushnet, Mass., asphalt plant, an Astec double-barrel 500-ton-per-hour drum-mix facility, provided all of the hot mix for the project including the latex-modified open-graded asphalt pavement mix. Injected into the mix at the Astec plant, the latex product is manufactured by BASF, The Chemical Company, and supplied by Rubber Roads, a distributor for BASF latex polymers.
According to Fred Mello, Rubber Roads consultant, the synthetic latex polymer increases the viscosity of the liquid asphalt, preventing the asphalt from settling to the bottom of the haul truck — a problem associated with open-graded mix because of the lack of fine aggregate. In addition, latex makes the hot mix more resistant to oxidation, a process that makes asphalt more brittle. Flexibility of asphalt is especially desirable in northern climates such as New England, where temperature swings can be extreme.
Mello noted that eight representatives from BASF facilities in Mexico and Panama observed Keating's plant and jobsite operations to gain field knowledge on the use of the product.