U.S. Studies "Warm-Mix" Asphalt Methods
NAPA, European producers to sponsor laboratory-research effort
By Tudor Hampton

Hot-mix asphalt may be due for a cool change as the National Center for Asphalt Technology gears up a research program to look at European methods allowing temperatures 50° F lower than normal. According to experts, "warm-mix" asphalt may improve paving performance and at the same time reduce emissions and odor.

"We have known for a long time that if we could reduce temperature then we could reduce emissions," says E. Ray Brown, NCAT director at Auburn University, Auburn, Ala. He says North American producers typically heat liquid asphalt cement and aggregate to between 300° and 325° F at the plant. Transporters maintain that temperature until delivering hot mix to the jobsite.

Two European vendors, in conjunction with the National Asphalt Pavement Association, Lanham, Md., are getting ready to underwrite an NCAT lab study costing $50,000 to $75,000, set to begin this summer. Scientists will evaluate temperature and performance, then move on to field trials a year later.

"Today, asphalt plants have been delisted as a major source of air pollution, but the more we can improve, the better," says Wayne Evans, Hubbard Construction Co. senior vice president in charge of asphalt operations in Orlando. A sister division of Hubbard and subsidiary of The Vinci Group, Eurovia Services, Rueil-Malmaison Cedex, France, in 2001 developed a fine admixture powder called Aspha-min. According to Evans, it is a synthetic zeolite, comprised of natrium aluminum silicate, which plants introduce into liquid asphalt and aggregate along with binding agents.

WAM foam is another test material, developed in 1995 by a joint venture of Shell Global Solutions, Petit Couronne, France, and Kolo-Veidekee ASA, Oslo. According to researchers, WAM foam is a process that blends soft and hard binders, making asphalt workable at a lower heat.

Brown estimates the methods would lower temperatures by at least 20%, and Evans believes the mixes may help plants save emission-control costs, which typically account for 30 to 50% of plant overhead. The products also may make asphalt easier to lay, he says. "The material is more fluid, so we may be able to achieve density easier, using use more static rollers instead of the more expensive vibratory rollers," says Evans.

But Mike Acott, president of NAPA, says the proof has yet to come, as NCAT researchers get ready to start tests in the lab and then move into field trials. "I would suspect this technology would take several years before it is embraced, but we think there is an opportunity here," he says.

Tandem-Drum Rollers
Front- and Rear-Drum Vibration
Bomag introduces the new BW266 and BW278 tandem-drum vibratory rollers. Built with fuel-efficient, EPA Tier II compliant 130-hp Cummins diesel engines, both models produce a maximum of 3,800 vpm. Offering a 66-in. drum width, the BW266 can generate up to 32,950 lb of centrifugal force, while the BW278 features a 78-in. drum width and a centrifugal force of 37,099 lb. The high vibration frequency allows both units to achieve a working speed of 4.3 miles per hour while maintaining a minimum of 10 impacts per ft. Compaction America Inc.; 309/853-3571;

Asphalt Testing Equipment
Accommodates Superpave Specimens
This rotary asphalt wheel tester uses three Hamburg-style wheels to continuously rotate the specimen. Its unique design takes advantage of the shape of Superpave Gyratory Compactor specimens and pavement cores. Each rotation of the specimen provides three load cycles, speeding up testing time for laboratories, highway departments and contractors. All data generated during testing is automatically saved to a floppy disk drive. Rut depth, loading rate and water bath temperature are recorded and stored in a format compatible with most office applications, such as Microsoft Excel. Pine Instrument Co.; 724/458-6391;

Horizontal Shaft Impactor
Solid-Steel, Three-Bar Rotor
UltraMax horizontal shaft impactor 04 is available as either a skid unit or a bare shaft crusher. Features such as a solid-steel, three-bar rotor and three-stage crushing action leave more asphalt cement on the stone, making recycled asphalt pavement processing more profitable for paving contractors that use the material in their mixes. It also is equipped with a 27 x 32-in. feed opening and produces 100-plus tons per hour. Eagle Crusher Co. Inc.; 800/253-2453;

Vibratory Roller
Oscillatory Compaction System
Designated HDO90V, this new model signifies a hybrid roller of the Hamm HD 90 Platform, in which the front has a conventional vibratory drum and the rear features the oscillatory technology. In the oscillation drum, two masses turning in the same direction cause a movement around the drum axle. The movement changes its direction of effect during one turn so that it generates an oscillating or rocking movement of the drum. Hamm Compaction, div. of Wirtgen America Inc.; 615/501-0600;

RD-11 Asphalt Roller Series
Cybernetic Design
This one-ton roller with a 35.4-in. drum width and a forward travel speed up to 414 ft per minute is available with either an 18-hp Honda or an 18-hp Vanguard engine. It delivers 3,000 lb of centrifugal force with lifts up to four inches on asphalt and 10 in. on soil. The RD 11 is equipped with dual drum drive and articulated steering as well as hydrostatic drive with infinitely variable forward and reverse speed. It also has an easy-to-read water and fuel sight gauge and removable panels for easy access to the engine. Wacker Corp.; 262/257-4131;

Paving Equipment
Meets Tier 2 Emissions Standards
Tier 2 Series of mainline and commercial pavers feature a 20 to 40% horsepower increase, while meeting U.S. EPA and CARB Tier 2 and Stage 2 emissions standards. A revamped cooling system features a new single-width, triple-element radiator that cools engine water, charge air and hydraulic oil. Additional features include a larger hydraulic oil reservoir, increased load bearing capacity and 20% increase in tractive effort. Cedarapids Inc., a Terex Co.; 319/399-4816;

Power Box Asphalt Paver
Two Fully Extendible Screed Options
Easy to operate and maneuver, the 1648 Power Box Paver is designed for small- to medium-sized contractors. Independent hydraulically operated augers can be located on either the material flow gate or on the screed extensions. These options allow the user to address the individual job application needs that exist on wide paving and narrow paving jobs. The paver also is equipped with a new dual-speed hydrostatic drive system. Gehl Co.; 262/334-9461;

High-Production Cutter Head
Manufacturer introduces the new AZ-480S magnum-powered reclamation/milling attachment. It mounts to the bucket of an existing loader, turning it into a magnum-powered asphalt destroyer with production capabilities of much larger, more expensive machines, the maker says.

New features on the AZ-480S include an active hydraulic depth control for accurate and easy depth adjustment, Zip-Loc hydraulic bucket locks for smooth operation, the Z-Mag cutter head that generates up to 20% more production and the patented Zip'n-Go bucket slot for fast loading and unloading.

The AZ-480S makes short work of most types of asphalt removal, including utility trenches, road reclamation, road repairs, soil stabilization and more. It can be transported easily on its own trailer towed by a standard pickup truck.
Asphalt Zipper; 888/947-7378;