The faster you play the drums, the smoother the roll sounds. The faster you work the drums, the smoother the roll feels.
It’s the new challenge of the compaction industry: making rollers vibrate fast enough to keep up with the Superpave technology, which, in turn, will produce a surface without premature buckles and crumbles.
“Some of these highways are subjected to some awesome loads by the trucking industry,” Dick Draper, vice president and general manager for Sakai, told ROADS & BRIDGES. “The Superpave product was designed to be able to withstand that type of high loading, and that product requires the high vibrations per minute in order to have the travel speed that’s required to keep up with the paver that’s laying the asphalt.”
The industry is getting more complicated, but rollers, for the most part, are sticking with the basic look. Practicing the trend of going out and asking what the user wants, many manufacturers are finding out the way to increase customer satisfaction is rather simple.
“We went to the asphalt contractors in North America and asked their operators and their superintendants on the job what they really wanted in the compactor, and they wanted high vibrations per minute in order to stay up with the paver, they wanted a low-profile machine and they wanted high visibility,” said Draper.
And the industry is seeing a hefty kick in sales even before funds for the Transportation Equity Act for the 21st Century come flying through. Marty Owens, senior marketing analyst for Dynapac, says business has been busy for the past year, mainly due to a rise in rental customers.
“Our sales to rent houses has almost tripled from 1998 to 1999,” he told ROADS & BRIDGES. “The rental industry is going to become a major player down the road.”
“Everyone keeps saying year-to-year that this is going to be the best year and then it’s going to fall,” Steve Wilson, manager of marketing services for Compaction America, told ROADS & BRIDGES. “We’re still riding that high and I think everybody is looking at pushing that window out again for at least another two- to three-year period.”
Riding high output
Hypac, manufactured by Compaction America, Kewanee, Ill., believes it has an uplifting idea for its C766C double-drum vibratory compactor: high output (HO) option.
The HO option boosts vibratory frequency and centrifugal force, permitting faster rolling speeds while maintaining compaction quality, according to the company. In low amplitude, the machine with HO option produces 3,800 vibrations per minute (vpm) and up to 22,425 lb of centrifugal force. In high amplitude, the unit can produce up to 29,775 lb of centrifugal force and 3,400 vpm.
The C766C is equipped with a Multi-System Performance Indicator, which allows the operator to input maximum working speed and automatic vibration start/stop as well as front and rear drum vibration frequency amplitude, and has pneumatic drum isolators that provide a cushion of air between the drum and the frame.
The roller is powered by a turbo-charged, 125-hp Cummins diesel engine.
The CB is back
Taking a second look, Caterpillar, Peoria, Ill., has released an “enhanced” double-drum vibratory asphalt compactor—the CB-634C.
Carrying an operating weight of 25,750 lb and a drum width of 84 in., the CB-634C is juiced by a turbo-charged Caterpillar 3116T engine rated at 145 hp and has a three-amplitude vibratory system. The roller develops 26,550 lb of centrifugal force per drum in high amplitude. For work on thinner lifts and tender materials, the machine can be operated at either medium amplitude, 19,643 lb of centrifugal force per drum, or low amplitude, which produces 8,865 lb of centrifugal force per drum. Vibration can be set for either front, rear or both drums.
The model has two water pumps, but only one operates at a time. The water tank capacity has been increased to 317 gal, and the drum spray system incorporates a three-stage water filtration.
Caterpillar has stepped into the 4-ton asphalt compactor size class with a double drum and combi model.
The CB-335D, powered by a three-cylinder Caterpillar 3013 liquid-cooled engine, has a combi configuration, a steel drum at the front and rubber tires at the rear. The 51-in. vibratory drum generates a frequency of 3,550 vpm and produces 5,620 lb of centrifugal force.
The CB-334D, which holds a four-cylinder Caterpiller 3014 liquid-cooled engine, is a vibratory double-drum machine. The drums, also 51 in. wide, produce 7,250 lb of centrifugal force and can generate 4,100 vpm.
Caterpillar offers three pneumatic compactors: the PS-360B, PS-150B and the PS-200B.
Here’s what they said
The industry made the suggestions, Dynapac, Schertz, Texas, made the CC522.
The double-drum vibratory asphalt roller is a direct result of a survey of roller operators and servicemen, as well as a culmination of years of research, according to the company.
Weighing in at 14 tons, the roller covers a standard 12-ft-wide asphalt mat in two laps with a 10-in. overlap. The 55-inch drums can generate 3,000 vpm.
Vibration and water controls are automatically turned on and off as the roller goes below a certain speed. The water spray system is comprised of a water pump at each drum with an emergency back-up, where one pump can wet both drums.
“It’s original design was for the new Superpave mixes, and it’s basically a customer-designed piece of equipment,” said Owens.
New to the U.S.
Ammann, distributed by Jacksonville, Fla.-based American Swiss Compaction and Multiquip, Carson, Calif., is sending over a series of tandem vibrating rollers to do the job on American highways.
The AV 95, a 9-ton asphalt compaction machine with double yoke steering, shifting cabin and four amplitudes, is being offered for the first time in the U.S.
The double yoke steering gives the model a turning radius of a 4-ton machine. Optional split drums are driven independently.
The AV 12 and AV 40 are tandem vibrating rollers which range from 1.5 to 4 tons. The rollers come with central articulation, water-cooled three-cylinder engines and fixed drum offset.
The AC series (AC 70, AC 90, AC 110, AC 120, AC 150, AC 180) are self-propelled vibrating rollers by Ammann. The machines come with a water-cooled engine and oiled submerged vibration bearing, and the drum drive system has a hydraulic torque adjustment. Vibration frequencies range from 2,160 to 2,400 vpm, while centrifugal forces per drum range from 20,200 to 46,125 lb.
“The Ammann roller has been very popular in Europe,” Steve Spence, product manager for Multiquip, told ROADS & BRIDGES. “The smaller size units come with zero-wall clearance, where there’s actually no drum supports at opposite corners of the machine so you can actually roll right up against a wall.”
Multiquip also distributes Rammax T-Series tandem ride-on vibratory rollers (T16, T23, T26 and T33).
On all four models, the double drums are offset to increase working width and allow maximum clearance, and a high-torque, water-cooled, three-cylinder Yanmar diesel engine offers two working speeds of 2,400 and 2,700 rpm (the T16 works at 2,400 rpm only). The two-speed system allows two different frequencies, centrifugal forces and travel speeds to adapt to different working conditions, according to Multiquip.
Sakai America Inc., New Castle, Del., believes it can run with Superpave technology with the introduction of the SW800 and SW850. Both machines can impact the asphalt at 4,000 vpm.
“Some Superpave mixes exhibit a tender zone as the mix cools,” said Draper. “Contractors needed to speed up their compaction process, but speeding up their vibratory rollers just stretches out the impact spacing . . . so it’s counterproductive. By offering 4,000 vpm impact frequency we can increase roller ground speed without sacrificing density.”
The SW850 offers a rolling width of 79 in. and produces over 33,000 lb of centrifugal force per drum, while the SW800 offers 27,000 lb of centrifugal force over 67-in.-wide drums.
The duo also has Sakai’s patented vibration system, which directs forces downward into the material and away from machine components and the operator.
Lengthening the company’s Superpave train is the TZ600, which is a pneumatic-tired intermediate roller.
No hassles, no worries
Bomag, a product of Compaction America, has figured out a way to drain one more process out of the think tank. Claiming it “the world’s first automatic vibration system,” the Variomatic is featured on the BW151AD-2 tandem vibratory roller.
The optional Variomatic system can eliminate the need for the operator to select the optimum vibration mode, and will adjust within one second from vertical mode to a horizontal orientation while rolling or standing still while the drum is still vibrating but not leaving the mat. The system also enables the roller’s force to be directed between the extremes of vertical and horizontal vibration, and every time the roller changes direction it will redirect the compaction forces to match.
The roller’s 66.1-in. vibratory drum produces a frequency of 3,420 vpm.
To provide close-in compaction around curves, or for efficient compaction of the longitudunal joint, the BW151AD-2 is designed with crab steering. Crab steering allows the operator to offset the drums approximately 7 in. in either direction, left or right, from centerline or while moving.
The BW138AD is related to the BW151AD-2. The BW138AD also is a tandem vibratory roller featuring 54-in.-wide drums that exert up to 11,925 lb of centrifugal force. The machine can reach frequencies of 3,240 and 3,600 vpm and has two scrapers per drum to reduce the risk of material pick-up.
Bomag also produces a pair of single-drum vibratory rollers (BW156-3, BW177-3) and a pivot-steer roller (BW180AD).
Make it a double
Fresh from the mind of Ingersoll-Rand, Bethlehem, Pa., is a pair of double-drum vibratory compactors, the DD-90HF and DD-110HF, designed for Superpave mixes and large paving applications.
The DD-90HF comes with a 66-in. drum width and offers 3,800 vpm, while the DD-110HF has a 78-in. drum and can produce 3,350 vpm.
Both feature an impact meter that measures the number of drum impacts per foot, allowing the operator to adjust speed and impact spacing, and are equipped with drum-wetting systems which consist of two complete, independent water supplies. The DD-90HF can hold 250 gal of water. The DD-110HF carries 320 gal.
The drum-wetting system of the DD-130, another double-drum vibratory compactor, has been upgraded. The system now boasts two 150-gal low-density polyethylene tanks, and the machine provides two complete water systems for each drum.
Rolling with 84-in. drums, the DD-130 features eight different amplitude settings that produce centrifugal force between 15,975 lb and 36,030 lb per drum.
Compacton testing equipment have the final say at asphalt paving project
There are foremen and superintendants at every site involving hot-mix asphalt, but it is the testing equipment that ultimately will determine what’s right and what’s wrong. The following is a brief overview of some of the products used to monitor all applications.
In binder ignition tests, as asphalt is burned the temperature rises substantially above the setpoint, peaks, and gradually returns to the setpoint as burnoff nears completion. Gilson’s HM-378 Binder Ignition System has a user-programmed furnace which remains locked for a designated period of time until the temperature returns to the set point.
The stainless steel case has a drop door to facilitate easier sample tray handling, and Kanthal A-1 heating elements are easily accessible for replacement.
The controller in the HM-378 has memory for up to 10 timed programs with selected chamber and afterburner setpoints, according to the Lewis Center, Ohio-based company.
Gilson’s Micro-Deval measures abrasion resistance and durability of mineral aggregates in 9.5 to 19 mm size ranges. The machine meets Canadian standards, and a provisional American Association of State Highway & Transportation Officials standard is under review.
Available in one, two or three tiers, the unit has one jar and abrasive charge for each tier as well as a magnet to assist with ball handling.
Test duration is controlled with a 0- to 15-hour electric timer.
Making sure everything checks out for the Pine Instrument Co., Grove City, Pa., is a pair of Superpave gyratory compactors.
The AFG1 is designed for field and laboratory use and stores data from the last 20 tests.
A built-in extruder permits easy removal of the specimen from the mold assembly after testing.
The test angle is continuously measured and displayed, and the angle of gyration is set at 1.25 degrees.
The operator can elect to test to a specified height or specified number of gyrations.
The AFGC125X conducts testing at the laboratory and can store data from the last five tests.
Manual extruding of the sample is produced by a hydraulic pump and the angle of gyration is 0.50 to 2.0 degrees.
Like the AFG1, the operator can elect to test to a specified height or specified number of gyrations.
Troxler’s gyratory compactor, Model 4141, is specially designed for smaller labs and construction trailers.
A one-button operation provides consistent samples, and parameters are changed by following on-screen menu instructions.
Accessories include GyroPave software that works with the Microsoft Excel spreadsheet program.
Troxler, Research Triangle Park, N.C., also has a gyratory compactor suited for Superpave work, Model 4140-B.
This compactor can be programmed to operate automatically or the user can manually control each compaction step. The system also can be programmed to compact specimens for a set number of gyrations or to a desired specimen height.
Troxler uses a patented method of angle induction, where the top of the mold is held in a fixed position while the angle is induced by offsetting the base of the mold. Rotating the offset base creates the gyratory motion with angle control and power efficiency, according to the company.
Verification values for the pressure, angle, height and rotational speed are stored after each calibration, and the operator may choose to print the results of each individual calibration or to generate a summary report that details all four parameters.
The MC-3 Portaprobe, manufactured by CPN, Martinez, Calif., stores up to 200 readings of test results with a project number and the date and time of test.
At the end of a test, the keyboard display provides a direct readout of all results, which includes wet density, moisture content, dry density, measurement precision, percent moisture, relative compaction and the air void percentage, simultaneously.
The depth of measurement is approximately 6 in.