Try not to get separated

By: Bill Wilson

This isn’t going to lead to a million-something march through the streets of Washington, D.C. However, the asphalt paver industry is on a crusade to end segregation.

There are two types of segregation: aggregate and thermal. With the advancement of Superpave, the separation of aggregate is becoming more prominent.

"Superpave is a much harsher mix with bigger stones, so the mix itself has more of a tendency to separate," Bob Ringwelski, product manager for asphalt pavers at Caterpillar, told ROADS & BRIDGES. "I think a lot of these issues that we talked about with segregation stems a lot from Superpave itself."

Some manufacturers believe the fight is about to be called. Material transfer vehicles, machines that reblend the mix as it leaves the truck and enters the asphalt paver, have been the popular choice for a possible solution.

"We feel like we’re the segregation killers in the business," Jeff Richmond, vice president of sales and marketing for Roadtec, told ROADS & BRIDGES. "We’re the only manufacturer today that builds a Shuttle Buggy and a material transfer vehicle where we will guarantee the elimination of truck-end segregation with virtually any mix."

But despite the recent favoritism, there is no guarantee the material transfer vehicle will survive the constant boom of innovation. Richmond thinks an integrated paver could be a possible replacement in the near future.

"This is where you would have a pick-up machine and/or a truck-dump elevator elevate the asphalt into a specialized hopper where you can do a significant amount of reblending," he said.

Ringwelski just sees dollar signs when asked what might happen five or 10 years down the road. No matter what method is used to prevent segregation, it has to be economical.

"I don’t think we’ve found the best solution yet," said Ringwelski. "The cost per ton to do some of this remixing is very expensive. I think as an industry we’ll try to find a way of preventing segregation at a cost of less than a dollar a ton."

As for solutions currently surfacing the country, ROADS & BRIDGES looks at some of the top asphalt pavers in the market.

Roadtec, Chattanooga, Tenn., wants to be noticed with its SP-100B Stealth paver.

The gravity-fed asphalt machine can work in combination with a Shuttle Buggy material transfer vehicle or an MTV-1000B material transfer vehicle to produce what the company calls "the ultimate in pavement smoothness."

The SP-100B comes equipped with a 10-ft standard vibratory screed or a hydraulically extendable vibratory screed.

Roadtec’s line of track-driven asphalt pavers includes the RP 185-10, RP 185-8 and RP 235. With a 234-hp diesel engine and oversized hydraulic components, the RP-235 is the company’s most powerful track paver.

Standard features include 16-in. polyurethane grousers, bogie-mounted track rollers and hydraulically activated tension rollers. The 8-ft RP 185-8 paver features an 8-ft standard vibratory screed or a hydraulically extendable vibratory screed that can pave widths of 8 ft to 15 ft, 6 in. The narrow width of the machine makes it maneuverable.

The RP 180-8, RP 180-10 and RP 230 are among the rubber-tired pavers offered by Roadtec. The RP 180-8 is an 8-ft-wide asphalt paving machine that incorporates 90% of the componentry of the 10-ft RP 180-10, including a 6-cylinder diesel engine. The narrow shipping width of this machine makes it a nonpermitted load, allowing for easy transportation. The RP 180-10 is a 170-hp paver that features dual operator stations, a direct hydrostatic drive, a standard fume extraction system, hydraulically raisable and tilted augers, sonar feed control and either mechanical or sonar automatic grade and slope control. The model comes with either a 10-ft standard vibratory screed or a hydraulically extendable vibratory screed that will pave as wide as 24 ft with extensions. The RP-230, a 234-hp rubber-tired paver, can be used for placement of base or fine materials.

Caterpillar, Peoria, Ill., was looking for consistency with velocity. Then came the AP-900B and BG-240C wheeled asphalt pavers, two machines that carry the company’s speed control system. This allows consistent speed to be maintained throughout a job.

The material handling system of the two models consist of a pair of feeders and augers as well as being hydrostatically driven. The variable-speed feeders and augers operate independently of each other, and the system also provides fully proportional control with manual override capability.

Two adjustable feeder gates allow the operator to meter the flow of material from the hopper to the augers. The auger drive and chain case are separated from the tractor, creating a gap between the feeder discharge and the auger frame. This gap provides improved material flow under the chain case and helps eliminate center-line segregation, according to Caterpillar.

A closed-loop hydrostatic propel system provides quality control of steering and propulsion. Two speed ranges are available through the two-speed motors and single-speed planetary wheel drives. Maximum pave speed is 400 ft per minute.

Both the AP-900B and BG-240C are equipped with a single operator’s station that slides from side to side.

Caterpillar beefed up technology in the BG-260C and AP-1000B wheel-type pavers. Some of the technological advancements include: enhanced propulsion capabilities; independent control of augers and feeders; system diagnostics through microprocessor controls; increased live feeder area; and reduced potential of material segregation.

A conveyor and auger drive eliminates feeder gates to adjust material volume. The conveyor-to-auger speed ratio can be adjusted to provide exact volumes of material. The result is slower running feeders that "always operate full of asphalt."

The pavers have outboard feeder drives. The feeder drive motor is positioned outside the mainframe, away from the feeder and the heat of the asphalt. The outboard drive allows for a narrower center chain cover resulting in improved material flow to the augers.

Another feature is Steer Assist, which slows down the drive speed on one side of the propel system and speeds up the other according to steering command.

The BG-260C and AP-1000B also have the speed control system. Similar models are the AP-1055B rubber-belted paver, AP-1050B track paver, BG-2455C rubber-belted paver and the BG-245C track paver.

A triple bogey is not necessarily a bad thing if you’re an asphalt paver operator. Caterpillar’s newest 8-ft pavers—the AP-650B and BG-225C—offer a "smooth" ride with the triple-roller rear bogey. The feature combines three sets of wheels into one bogey that evenly distributes the weight of the machine and the screed across the length of each track.

The propel system in the AP-650B and BG-225C incorporates pave, travel and maneuver modes for versatility. Maximum pave speed is 220 ft per minute.

Cat’s speed control system, conveyor and auger drive and outboard feeder drives also are available on the machines.

Nowhere to go but up. That’s the philosophy of Global Asphalt Products Inc., Chambersburg, Pa. The company claims it takes the continuous rubber track drive system to the next level with the Pro-Pav Series Swiftrac 1110RT asphalt paver.

The model, which has a top speed of 13 mph, has a final drive that utilizes two hydraulic motors to deliver four speed ranges with shift on-the-fly control.

A fully proportional feeder system has standard ultrasonic material level sensors, and the augers are hydraulically adjustable from 5 to 10 ft above the ground.

The Swiftrac 1110RT is available with four different screeds. The Pro-Pav Series HS 1020 is a 10 to 19 ft, 6 in. screed with rear mounted extensions and telescoping pre-strike offs. The HS 1017 provides paving widths from 10 to 17 ft with rear-mounted extensions and telescoping pre-strike offs. The ES 1017 creates paving widths from 10 to 17 ft with front mounted mini-screed extensions, and the FS 100, a fixed width 10-ft screed, is available with or without hydraulic strike off extensions.

The 1110W AWD is an all-wheel drive asphalt paver. When engaged, the AWD provides up to 90% more tractive effort than a conventional two-wheel drive machine and 34% more than a machine equipped with optional front wheel assist, according to the company. The system is designed so that power is supplied to each of the four front bogie wheels independently.

The Pro-Pav Series portal axle drive system provides true differential steering and the option of differential lock or modulated steer assist pedals.

The 1110W AWD is available with the same four screeds as the Swiftrac 1110RT.

Global Asphalt performed a complete redesign on the 780WB 8-ft rubber tired paver.

The 17-ft-long roadbuilder boasts 190 ft3 hopper capacity, has an 8-ft, 6-in. inside turning radius and a top speed of 12 mph. The feeder system is fully proportional and comes standard with ultrasonic material level sensors.

The 780WB is available with three different screeds. The Pro-Pav Series HS 814 is an 8 to 14 ft screed with rear mounted extensions and telescoping pre-strike offs. The ES 813 provides paving widths from 8 to 13 ft, 6 in. with front mounted mini-screed extensions. The FS 80, a fixed width 8-ft screed, is available with or without hydraulic strike off extensions.

Blaw-Knox Construction Equipment Corp., a division of Ingersoll-Rand Co., Mattoon, Ill., now has an extended family. The company recently introduced two new power extendible UltiMat Screeds for their high capacity and mid-sized asphalt pavers.

A double extension mechanism permits both the basic 8-ft UltiMat 16 and the basic 10-ft UltiMat 20 to extend to twice their basic width.

The screeds’ 37-in. base provides stability and initial material compaction while the front mounted extendible sections, both of which are equipped with heat and vibration, produce a more consistent head of material pressure across the face of the screed at any operating width.

Screed heating is automatically controlled by the screed temperature controller, which controls the amount of power required to maintain the desired temperature setting and maintains fully automatic temperature control for uniform heating across the main and extendible section screed plates.

The wheel-mounted PF-2181 from Blaw Knox is an 8-ft asphalt paver/finisher with a maximum paving width capability of 21 ft.

A two-speed hydrostatic direct traction drive system eliminates 70% of mechanical drive train componentry and offers variable paving speeds up to a maximum of 260 ft per minute.

The PF-4410 is an 8-ft paver/finisher with a maximum paving width of 25 ft.

Continuous, flexible, high-speed rubber tracks with positive, non-slip cog/ socket drives combine the traction and flotation of a track machine with the mobility and rideability of a wheel machine.

Dynapac believes it has the right blend of technology for the mix of Superpave. Forming the paver line for the company are the F 30 4W, F 25-4W, F 25-C and the F 30C. The F 30 4W and F 25-4W are wheeled pavers, while the other two drive on a set of tracks.

The F 25-4W and F 25-C come with a telescopic and hydraulically extendible screed that is infinitely variable out to 14 ft, 9 in. With bolt-on extensions, paving widths of 23 ft can be achieved.

The hopper in both models is designed to carry up to 15 tons of storage capacity. Separate and independent dual bar feeders deliver material from the hopper to the auger, and the laydown capacity of the F 25-4W and F 25-C is 700 tons per hour.

Dynapac’s auger system features two separate and independent hydraulically driven augers with infinitely variable speed control. Each side is controlled by limit switches or proportional sonic sensors.

The F 30 4W and F 30C are a bigger version of the F 25-4W and F 25-C. The machines have a screed that is infinitely variable out to 18 ft, and can pave at widths of over 26 ft with bolt-on extensions. The hopper can carry 25 tons of storage capacity. The laydown capacity of the F 30 4W and F 30C is 2,600 tons per hour.

Gilcrest Equipment Co., Holdon, Mo., parent company of ProPaver, recently introduced the ProPaver 814 MPC.

The prized piece of these machines is a programmable microprocessor which controls all major funtions.

The 814 MPC, which can pave widths ranging from 4 to 7 ft and 8 to 14 ft, also has two remote hand-held screed controls for operation on or off the machine.