Compaction Rollers and Testing Equipment Work to Provide a Quality Road Surface

Asphalt Article December 28, 2000
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Double-drum rollers

Compaction America Inc., Kewanee, Ill., offers the Hypac C766C vibratory double-drum compactor, designed with a computer control system that includes a microprocessor display keeping the machine's performance in clear view of the operator.

The microprocessor provides consistency in system settings and performance by constantly displaying the unit's speed, impacts per foot and front and rear vibration speeds. It also offers a "human engineered" operator platform and a travel joystick with integrated thump-tip vibration control.

When setting operating parameters, the travel joystick control levers, mounted to each side of the operator console, provide forward, neutral and reverse direction control allowing for manual execution of the vibratory system, speed and direction with just one hand. The roller produces 3400 vibrations per minute (VPM) in low amplitude and 3200 VPM in high amplitude with a 66 in. wide drum. The CC501 vibratory asphalt compactor from Dynapac Compacting and Paving, Schertz, Texas, is one of the largest double-drum rollers available that can handle a number of applications including Superpave mixes.

Bruce Truesdale, vice president of marketing for Dynapac said, "The CC501 is the largest asphalt roller on the market. Dealers and contractors are finding out that it is preferred on Superpave projects."

With an operating weight of over 37,375 lb, it can achieve density in very few passes providing a high productivity rate. With a 60-in. drum diameter and dual amplitude, the roller can work on Superpave mixes sooner while minimizing asphalt displacement or cracking. For thick lifts, the roller produces 42,075 lb of centrifugal force at high amplitudes.

Caterpillar Inc., Minneapolis, is represented in the intermediate sized double-drum vibratory asphalt compactor market by the CB-534C model. The unit is a high-production compactor that competes in the 8.0 to 11.3 metric ton range. With an operating weight of 20,270 lb and a drum width of 67-in., the roller has a two-speed, electric throttle to control engine RPMs.

A three-amplitude vibratory system on the unit allows it to work on thin, medium or thick lifts, helping it to match centrifugal force with various material characteristics. In high amplitude, the unit develops 26,550 lb of centrifugal force per drum. For working on thinner lifts or tender materials, the machine can be operated at either medium amplitude for 19,643 lb of centrifugal force, or low amplitude for 8,865 lb of centrifugal force per drum. Vibration can be selected for either the front or rear drum.

The two-speed throttle consists of a two-position switch on the instrument panel, replacing the manual, cable-style throttle. The operator can select from two water pumps, both of which slope away from the operator to increase visibility, and are separately located in the front and rear, to supply water to both sets of drum spray bars.

Vibromax America Inc., Racine, Wis., decided to start anew at the drawing board when designing their model 263 tandem roller.

"Rather than upgrade an older model machine, this roller was designed from the ground up," said Larry Kapellusch, vice president of operations for Vibromax America. "We put the operator in the middle of the machine and tapered the water tanks to provide better visibility to both drums. Its operator-friendly, compact design offers the tightest radius and shortest length in the industry."

The 263 tandem roller for small and medium-sized paving jobs has a drum width of 47-in. and features a three- cylinder Kubota diesel engine.

Propulsion is provided by a reliable high torque Poclain motor that allows up to 40%gradeability. It also features a new ergonomic operator's platform with a single control lever allowing for fingertip operation, automatic vibration off in neutral, pressurized intermittent sprinkler system, full instrumentation and centralized hydraulic test ports.

Hamm Compactors Inc., Irving, Texas, offers the improved DV 8 model compactor.

"Our new DV 8 model double-drum vibratory roller, offers improvements such as the new water tank design and a new sprinkler/scraper system," explained Udo Boersch, vice president of Hamm. "In addition, we've added a tiltable operator compartment and swivel seats. It has the latest series Deutz engine that meets or exceeds EPA emission and noise standards."

The 10-ton machine has a working width between 66-104 in. and is available in double steel drum or combination figures. High frequencies, plus the combination of steel and rubber, make the roller a versatile machine for HMA, roller compacted concrete, cement-treated base, cold-mix asphalt and recycled asphalt. The drums are split and each are driven by a separate drive motor, allowing the machine to operate on tight curves while eliminating asphalt scuffing.

The model features offset capabilities, which allow the machine to operate around manholes, along curbs and joint areas. The direct hydrostatic vibratory drive is equipped with dual amplitudes and variable frequency ranges of up to 3000 VPM. The roller also offers a rigid frame with independent steering to the front and rear.

Ingersoll-Rand, Bethlehem, Pa., rolled out the DD-70 high- performance, double-drum vibratory asphalt compactor for use in commercial, residential and roadway pavement compaction applications. It features 57-in. drums that are 41 in. in diameter with a shell thickness of over 3/4-in., increasing compaction productivity and drum life.

With an operating weight just under 15,000 lb, the machine features eight different centrifugal force outputs between 8,970 lb and 17,900 lb per drum, with automatic reversing eccentrics.

It is powered by a naturally aspirated Cummins 4B 3.9 80-hp at 2500-RPM engine. Propulsion is through efficient low-speed, high- torque direct drive motors on each drum. The drum-wetting system features two 97 1/2-gal tanks with variable flow control for optimum water utilization. The maneuverable DD-70 offers an outside turning radius of 189 in., a curb clearance of 22 in. on each side and a narrow 3 1/2-in. wall clearance.

Multiquip Inc., Carson, Calif., is the U.S. distributor for the Rammax Maschinenbau GmbH T-Series Rammax T26 tandem ride-on vibratory roller.

Steven Spence, compaction product manager for Multiquip said, "There are a combination of features that are unique on the T26. In- line or off-set drums allow the roller an easier guide against edges because the operator will only need to watch the front roller. A folding roll over protection system is unique on this roller in addition to dual level RPMs for the engine allowing different VPM levels for different applications. Also, a vibration-isolated drivers platform allows for a smoother ride."

It has a drum width of 48 in. and weighs approximately three tons. Double drums are offset to increase working width and allow maximum clearance. Vibration in both drums ensures a smooth, even surface on asphalt and soil/gravel sub-bases. A high-torque, water- cooled, three-cylinder Yanmar diesel engine offers two working speeds of 2,400 and 2,700 RPM. This allows two different frequencies, centrifugal forces and travel speeds to adapt to different working conditions.

The Wacker Corp., Menomonee Falls, Wis., RD 11 vibratory asphalt roller was designed for the compaction of level sub-layers and finish layers on road repairs, driveways, parking lots or any asphalt surface.

Jim Layton, marketing communications manager for Wacker said, "In recent years, a niche market for this sized roller has appeared. National rental chains have noticed a demand for this roller and accepted the roller by putting more and more units into their fleet, most of which are being rented by small contractors."

The cost-efficient, one-ton machine offers dual-drum drive and articulated steering for accurate control. A hydrostatic drive with infinitely variable forward and reverse speed produces a smooth asphalt finish in conjunction with the front drum vibration with static rear drum. When the front drum vibration is in forward travel, a breakdown pass by the front drum is followed by a static finish pass to smooth the asphalt surface. The vibratory rollers have a 35.4-in. drum width, forward travel speed up to 414 ft per minute while producing 3,000 lb of centrifugal force with lifts up to 4 in. on asphalt.

Sakai America Inc., New Castle, Del., offers the SW 250 double-drum vibratory model that brings big machine features to smaller jobsites like parking areas, road shoulders, small roadways, driveways, bike paths and recreation areas.

"We wanted to provide a ride-on roller for small jobs which offered the same features found on larger rollers," said Dick Draper, vice president/general manager for Sakai America. "The unit is capable of handling both small- and medium-sized projects providing an end result equal to what is expected from large rollers. This is a unit that can handle all types of compaction and achieve the density required."

The roller features a hydrostatic drive, machined vibrating drums with high centrifugal and static force outputs and a rust-resistant pressurized spray system, in addition to a fuel-efficient, water- cooled diesel engine. It operates at a weight of 3,505 lb with a 39.5- in. drum width, a 22-in. drum diameter, 2,070 lb of centrifugal force per drum and 3,150 VPM.

Stone Construction Equipment Inc., Honeoye, N.Y., offers the WolfPac 6400, a 47-in. asphalt roller for high-volume compaction.

"The WolfPac 6400 is ideal for larger asphalt jobs, yet works well in confined areas," said Kathy Reissig, marketing service manager for Stone Construction. "Contractors have been telling us that they like the comfort and ease of use of the roller."

This double-drum drive, double-drum vibration, articulating roller provides power and performance for base binder and finish coats. With an operating weight of 6,383 lb, the unit articulates 30° right or left and oscillates 15°. It has variable vibration in both drums or the rear only. Double or single vibration can be selected with a switch. It offers 6,518 lb of centrifugal force at 3060 VPM.

Single-drum rollers
Single-drum rollers produce similar results when compared to the double- drum rollers. In addition to their double-drum roller, Compaction America Inc. also manufactures a single-drum roller, the Bomag BW 213D-3.

According to Steve Wilson, manager of marketing service and product manager for Compaction America, "The 213D-3 is a third generation design. We went back to the drawing board for this model and designed it around features that contractors found to be most useful. For example, emphasis was placed on increased operator comfort in order to produce better benefits and reduce operator fatigue."

The roller features higher static linear load for improved performance, while wider clearance between the frame and drum, in conjunction with dual scrapers, prevent buildup of material. Specially developed anti-slip control (ASC) gives the roller climbing performance making grades of more than 500attainable.

By monitoring the slip potential between the drum and rear rubber tires, the ASC automatically adjusts the hydraulic flow between these components to deliver optimum performance for operation on severe grades or difficult traction conditions.

Pneumatic rollers
Pneumatic design rollers are commonly used for compacting trimmed subgrade or aggregate base.

Madison, S.D.-based Rosco Manufacturing Co.'s Tru-Pac 915 pneumatic-tired roller offers an articulated design which provides true-tracking and full-width compaction, especially in tight areas. Bob Shaw, director of sales and marketing for Rosco, said "Rosco approaches compaction somewhat differently than others do. Where some will use a rigid axle through each group of wheels, we independently oscillate the wheels to maintain constant surface contact. This enhances the natural kneading process and when coupled with the higher ground contact pressures, achieves substantially greater compaction."

Powered by a Cummins four-cylinder diesel design, the machine produces 76 hp at 2,500 RPM. The hydrostatic wheel-motor drive provides infinitely variable control of machine speed from 0 to 15 mph.

Ballastable up to 30,050 lb, each of the nine wheels delivers approximately 3,500 lb of compactive force directly to the work surface.

Gauging asphalt density
Density gauges, some of which are nuclear, are effective tools in the quality control programs of highway agencies, inspection testing firms and contractors. Selecting the correct gauge will save time and money, improve quality and reduce the chance of disputes, penalties or possibly, legal action.

Schenectady, N.Y.-based TransTech Systems Inc.'s Pavement Quality Indicator (PQI) is designed to acquire quick and accurate pavement density data.

"What makes the PQI technology so useful is its ability to provide an accurate, near-instantaneous measurements of pavement density," said Harry Apkarian, chairman and CEO of TransTech. "It has been long accepted by pavement engineers that the density of HMA is the most important construction variable in the long-term durability of paved surfaces."

Pavement readings take just five seconds and are accurate and repeatable. The unit delivers non-destructive asphalt density measurements, without the need for strict licensing and usage procedures that are inherent in nuclear instruments. It weighs less than 16 lb and can be used by virtually any member of the paving or QC/QA crew with little training.

"The PQI is particularly well suited for use on Superpave jobs, as well as on SMA and polymer-modified mixes where the critical parameters for pavement lay down and surface rolling are narrow," added Raymond J. Piascik, TransTech president. "It offers the laydown and quality control crew a way to obtain the compaction data they need to help achieve better compaction and a more uniform surface. What's more, the repeatability of the PQI is comparable to alternate, nuclear-based methods of density measurement."

CPN International Inc., Martinez, Calif., manufactures the MC-3 Portaprobe nuclear density/moisture surface gauge with 8-in. depth measurement in 2-in. increments for on-site measurement of density and moisture content of construction materials including soils, soil aggregates, concrete and asphalt pavements.

"Test results are available at the time of placement and compaction- when corrective action can be taken," said Doug Carter, technical support manager for CPN. "This saves money and reduces contractor delays in work. Nuclear gauges improve quality control, economy and timeliness of acceptance/rejection decisions as well as adherence to project scheduling."

It has two density modes of operation: backscatter and transmission. The backscatter settings provide non-destructive tests and are most often used for asphalt and concrete pavements where drilling a transmission hole is not feasible. A microprocessor provides direct reading of wet density, dry density, moisture content and relative density upon entering maximum values.

Humboldt Scientific Inc., Raleigh N.C., recently introduced the "EZ" series of nuclear density/moisture gauges.

"We listened to our customers and as a result, the 'EZ' was the answer for them. The responses we have received thus far have been extremely positive," said Mahir Al-Nadaf, Humboldt Scientific vice president.

The "EZ" series gauge is menu-driven and includes built-in test routines. It features a new trigger handle for source depth adjustment, a backlit liquid crystal display with fewer keys via a menu driven keypad, real-time clock and self-calibration. The unit also features totally contained automatic indexing, thin- lift asphalt measurements and trench correction while storing up to 320 measurements that can be transferred to a computer or printer via an optional infrared RS232 port. The gauges can be equipped for measurement depths of 8 or 12 in. in 1- or 2-in. increments.

While not all of the density gauges mentioned above are nuclear gauges, they represent ways to ensure compliance with method or end-result specifications for longer-lasting asphalt pavements. The equipment should be versatile and at the same time, contain the features needed for inspection testing. Gauges can simply calculate and display test results that are recorded in a field notebook or have storage and download capabilities via a serial interface. Also, nuclear gauge operators must have received certification training in safe and correct use of nuclear gauges on asphalt pavements.

Gyratory compaction equipment
Gyratory compactors measure the thickness of asphalt and have shown to provide the best simulation of the long- term effect of traffic on pavement.

Pine Instrument Co., Grove City, Pa., manufactures the AFG1 mobile gyratory compactor developed for field QC/QA applications. Designed with the asphalt contractor in mind, the new unit is cost-effective, lighter in weight, portable with integral wheels and operates at 110 volts. It provides all the test data needed to meet the current Superpave asphalt mix design requirements at the job site or in the lab.

Data from 20 previous specimens are stored in the unit's memory. Operator input is required only when changing the number of gyrations.

Every specimen is compacted with a fixed angle, consolidation pressure and rate of gyration to assure the repeatability of test data. Control of all test functions is provided by an embedded industrial controller. The pressure, angle and rate of gyration are calibrated at the factory, according to Superpave test specifications.

An emphasis on Superpave design and quality control is the goal of the Gilson Co. Inc., Columbus, Ohio, the exclusive provider of the portable Brovold gyratory compactor.

Approved by the Federal Highway Administration (FHWA), the gyratory compactor duplicates compacted mix specimens produced by other compactors. In use, the heated mold can be loaded with mix before or after placing it in the retaining cylinder. Once the gyrator head is swung into position, hydraulic loading to 600-kPa vertical pressure occurs rapidly and compaction proceeds via automatic control until desired specimen height or number of gyrations is reached.

The monitored gyratory angle may be dynamically adjusted to maintain 1.25 /- 0.005 degrees as held precisely without moving parts via the patented design. Compaction progress is tracked on an LED display, and data is downloaded continuously to a PC for added displays and computations. At the user's option, the compacted specimen can be automatically, hydraulically ejected from the in- place mold or the mold and specimen may be removed together for external ejection.

Asphalt pavement analyzer
Conyers, Ga.-based Pavement Technology Inc., an Astec Co., offers the Asphalt Pavement Analyzer (APA), a multi-functional loaded wheel tester used for evaluating permanent deformation, fatigue cracking and moisture susceptibility of both hot and cold asphalt mixes.

It features fully automatic, continuous measurement of rut profile under the wheel load. It can also test the asphalt specimens in dry conditions or submerged in water. The APA has the ability to develop the desired contact pressure, temperature and moisture conditions during testing and is capable of testing both rectangular and cylindrical-shaped samples.

Any number of compaction methods including gyratory, vibratory, kneading and Marshall may be used to prepare the samples. Roadway slabs and cores can also be tested.

The Georgia DOT began using a loaded wheel test in the mid '80s to predict rutting potential of mix. The APA is now required as proof testing for HMA placed on state highways and several studies have proven the APA capable of recognizing mixes that are likely to fail under traffic.

Asphalt content tester
An environmentally friendly, cost- effective method of determining asphalt content is Dubuque, Iowa-based Barnstead/Thermolyne's, NCAT asphalt content tester. The tester's ignition method reduces testing time on lengthy solvent extractions to between 30-45 minutes. A built-in ceramic filter and high temperature afterburner helps reduce emissions. The large chamber, 14-in. x 14-in. x 14-in., can accommodate samples up to 4000 g and utilizes a standard 30- amp electrical service.

Profilograph
Measuring smoothness of the surface is essential to any operation. Paveset America LLC, Denver, Colo., manufactures the Model ES2000 profilograph, which gathers two wheel paths of smoothness testing data simultaneously.

Steve Dunn of Paveset Sales said, "With more and more state agencies and engineering firms specifying smoothness and ridability on their projects nationwide, Paveset has designed the ES2000 to successfully complete a project in a safer, more efficient manner while maintaining an emphasis on lower cost."

The unit correlates to the traditional "California-type" profilograph and is a completely portable, towable, self-contained unit manufactured so one person can operate it from inside the towing vehicle. The unit's trailer-mounted sensor beams automatically plot level and crossfall changes, gathering cross- sectional information every 5 m longitudinally and 2.75 m transversely. The data is then stored into the computer at a speed of 5 kmph. Upon completion, a plot of the surface profile and cross sections can be produced by the windows operating system software.

 

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