Tags
Aggregates Equipment
Asphalt Equipment

Asphalt segretation busters – protect your reputation

For every ton of asphalt paved, your reputation is on the line. Asphalt producers and paving contractors take pride in delivering a durable road that lasts for 15 or 20 years or longer.

Sending segregated mix to the jobsite or laying a mat with patches of segregation can ruin a company’s reputation, not to mention significantly affect the bottom line. No matter where segregation occurs – in the aggregate stockpile, at the plant, on its way to the jobsite or behind the screed – it must be addressed. If not, the paved road suffers distresses such as raveling, rutting and cracking, which leads to costly rehabilitation ahead of schedule.


Manufacturers have been working with asphalt producers and contractors to develop equipment to help mitigate segregation occurrences. And there are several tactics that both producers and contractors can implement to reduce segregated mix. 
 
Mixing it up
Prior to making the mix, the way producers handle aggregate has a profound impact on segregation. Building aggregate stockpiles in layers with radial stackers vs. large conical shaped stockpiles reduces aggregate segregation, especially when it comes to larger size stone. Loader operators can also help the process by blending the material from the fine and coarse areas of a segregated stockpile.


At the plant, operators should keep cold-feed bins as full as possible to avoid larger aggregate from separating from the fine material. “To promote proper aggregate gradation, many producers are now using more cold-feed bins to store different stone sizes,” says Joe Musil, senior engineering fellow with Terex Roadbuilding.


Today’s asphalt producers incorporate more additives in the mix, and they must pay attention to additive sizing and introduce these items at the right point in the mixing process. Recycled asphalt product (RAP) and shingles, baghouse fines and warm mix asphalt all have their proper timing for introduction into the drum, and the mixer must have the flexibility to accommodate all the different additives.


“The drum is the ultimate commingler of the material, and that is why Terex asphalt plants have mixing zones that retain material between two and four minutes, much longer than the 45 to 60 seconds experienced with pugmills,” says Musil. “Long mixing zones help to avoid asphalt ‘balling’ of fines and deliver more uniform temperatures throughout the mix when introducing RAP and shingles into the design.”


When loading transport vehicles from the silo, using the three-dump method – loading two batches at each truck end and the final batch in the middle – will avoid large particle run-off to the truck’s sides and ends. Also, according to Terex Asphalt Paver Application Specialist, Bill Rieken, the type of truck used to transport asphalt makes a significant difference in reducing particle and thermal segregation.


Rieken says that end-dump trucks are the least preferred vehicle, especially with mainline and highway paving. “A dump truck is basically a box, where more of the asphalt comes into contact with the metal, which cools the asphalt at the ends,” he says. “The mix will segregate as the particles roll to the truck’s sides and ends during transport to the jobsite.”


Live-bottom trucks offer more protection against material and thermal segregation during transport. There is less surface area for the asphalt to come in contact with, so less cooling takes place, and the bed is shaped like a “V” to reduce particle segregation. 

Smooth and consistent
No matter if it’s warm mix or hot mix asphalt, paving contractors have equipment options to mitigate segregation occurrences at the site and, in some regions, this additional equipment is a requirement to meet government specifications. “Some specifications are so strict for mainline paving, that they cannot be met with a traditional slat paver alone,” comments Rieken.


Material transfer vehicles (MTVs) and devices (MTDs) are arguably the contractor’s best allies in the battle against segregation. However, there are key design differences, so contractors must carefully review the equipment options to ensure they are getting the right machine for the job.


Early MTV designs offered large storage capacities and some reblending capabilities. “The intent of those first designs was to allow crews to pave continuously to eliminate truck-end segregation,” explains Rieken. 


A newer generation of MTVs builds on the continuous paving benefits of previous designs, offers improved reblending capabilities and lowers ground contact pressures.


New innovations of variable-pitch, counter-rotating auger sets, like those found on the Terex CR662RM RoadMix MTV/paver, thoroughly reblend 100 percent of the mix to virtually eliminate thermal and material segregation. Low machine centre of gravity lowers the conveyor’s discharge point to lessen the chance of drop segregation. Also, track drives reduce fully loaded ground contact pressure to less than 20 psi, eliminating many of the issues associated with wheeled MTVs.


Low psi MTVs usher in the ability to be used on base lifts for reducing material segregation. Fear of subbase rutting with high psi wheeled machines has led many government specifications to limit MTV usage to the top paving lifts. “This is counterintuitive and counterproductive,” says Rieken. “Base mixes are made with larger stone sizes that are more prone to segregate, so we should be using MTVs on the base lifts. We have customers using the CR662RM RoadMix to pave base lifts, but it cannot be used as an MTV by spec.”


Similar to MTVs, MTDs establish continuous paving and can be used in conjunction with either dump truck or windrow paving. Unlike MTVs, these machines attach to and are guided by the paver, eliminating the need for an additional operator. Some, like the Terex MS-4 Mat Smoothness Machine, have shock-absorbing push rollers to eliminate truck “bumping” and screed settling. Several designs will also reblend material and have a low discharge height to eliminate drop segregation.


For contractors working with mixes prone to particle segregation – such as Stone Matrix Asphalt (SMA) – who don’t want to use a transfer vehicle or device, Terex Remix Anti-Segregation System pavers offer an alternative. Replacing the traditional slat conveyor with two sets of two counter-rotating augers, these pavers offer the same aggressive reblending capabilities as the new generation MTVs with the added benefit of doing so at the last stage of paving. This combats material as well as thermal segregation.

Segregation busting advances
Without adding specialized equipment to the paving train, a properly sized hopper insert goes a long way in reducing segregated mix. Inserts channel asphalt directly into the paver’s conveyor system – whether traditional slat or Remix counter rotating augers – to create a live bottom action that reduces particle segregation. Offering extra surge capacity to aid in continuous paving, the hopper insert design promotes a natural reblending of material and prevents larger, cooler material from building up in the hopper’s wings.


Rieken cautions contractors not to think that bigger is better. “Insert size,” he says, “must be matched to the paver hopper, or material will pool off to the sides, which will flow into the conveyor as the asphalt level drops. This results in random patch segregation.”


At the screed, consistency is paramount in reducing longitudinal segregation. Operators must monitor that the ratio pots or flow gates are set to deliver enough, but not too much, material to the spread augers so that they run continuously. If the augers are allowed to spin too slowly, larger aggregate drops off at the outboard bearing support, which results in longitudinal segregation. 


A major topic of concern today is centreline segregation, which results in top-down cracking. This occurs under the auger chain drive, and manufacturers counteract this problem by including variations of reversing augers to force material under the housing. Creating material confinement through lead crown adjustments and housing baffles mitigates this form of segregation.


On mainline pavers like the Terex CR600 Series, manufacturers are replacing the centre gearbox altogether by relying on outboard drive motors for the spread augers. “If you eliminate the centre drive housing, you eliminate centreline segregation,” says Rieken. With outboard drive, the auger sections back up to each other, leaving no separation in the centre. This eliminates the need for a centre gearbox drive and reversing augers.  

Back to basics
Before adding equipment to the paving train and before searching out paver options, paving success ultimately comes down to training the operators. Crews must be thoroughly educated in correct paving techniques and how to properly use each piece of equipment.


Crews should know the capabilities and limitations of the paving equipment. No amount of equipment will end segregation unless it’s operated in the correct manner.


Manufacturers work with contractors at the jobsite to help crews get the most out of their equipment. Additionally, contractors can attend equipment training schools at the factory like those offered through Terex Roadbuilding University.

Five keys to help prevent material and thermal segregation
Beyond equipment selection and following proper paving techniques, Rieken leaves the operators he trains with five keys to help prevent material and thermal segregation.


“Keep material confined; avoid dropping it; prevent mix dribbling; pave in a smooth, uniform and uninterrupted fashion; and don’t spill asphalt in front of the paver,” he says.
 

Company Info

Related News

Tags
Aggregates Equipment

Superior Industries Completes Acquisition of Crushing and Screening Manufacturer Clemro

Superior Industries, Inc., a major American manufacturer and global supplier of bulk material processing and handling systems, has officially completed an acquisition of Clemro Western Ltd. Based in Calgary, Alberta, Canada, the 30-year-old company is known for manufacturing jaw and cone crushers, incline and horizontal screens, and belt and grizzly feeders.

According to Superior, the addition of these product lines allows the company to increase its bulk handing portfolio for customers in construction aggregates and mining applications. In addition, Superior says the acquisition was appealing because of Clemro’s heritage as a family owned and operated company with a history of high production values and technological advances.

Read More

Tags
Asphalt Equipment

Skid-Mounted Sealcoating Machine

The 1,500-gallon capacity of the ESSP 1500S skid-mounted sealcoating machine reduces the time associated with refilling the tank on large projects and the number of trips a contractor needs to make to the sealer manufacturer or distributor. In addition, the unit’s electric super sand pump (ESSP) system features a variable speed control and produces as much as 100 gpm, the fastest transfer rate among piston pumps on the market. With this system, operators can cover areas up to 40 percent faster than diaphragm pumps.

The 1500S features an in-line surge tank that reduces material surging to ensure continuous flow of material for uniform coverage. The hydraulic agitation system with chain reduction features a unique three-blade design; the blades are offset to ensure two blades are in the material at all times, which produces a more thoroughly mixed product.

Read More

Sponsored Content

Introducing the 323F with Cat GradeControl

The new Cat 323F is a purpose-built machine powered by a fuel-efficient Tier-4 Final engine. With plenty of counterweight, robust structures, a state-of-the-art hydraulic system, and Cat Grade Control Depth and Slope* you can move tons of material – literally – all day long with tremendous stability, speed, and precision.When you add in a quiet operator environment that keeps you comfortable and productive, easy-to-reach service points that make your routine maintenance fast and simple, and multiple Cat work tools that help you take on a variety of tasks, you just won’t find a better, more efficient 23-ton excavator – any place, anywhere.

GET MORE INFORMATION

Tags
Asphalt Equipment

Trailer-Mounted, Spray Injection Pothole Patcher

Cimline has redesigned their successful DuraPatcher trailer-mounted spray injection pothole patcher, popular with municipalities that use a dump truck to tow the patcher and supply the aggregate.

The new DuraPatcher ECO combines environmental, safety and cost saving features. The Tier IV diesel engine, with 18 percent better fuel economy, powers the blower for the spray injection process.

Read More

Join our mailing list

Latest headlines
delivered to you weekly

Heavy Equipment Guide
Tags
Aggregates Equipment

IROCK Crushers Offers Diesel-Powered Sidewinder Crusher

IROCK Crushers has responded to customer demand with the introduction of a diesel option for its line of Sidewinder crushers. IROCK now offers the Sidewinder-15 with a 350-horsepower Caterpillar C-9 diesel engine, which powers a 100-kilowatt generator for full on-board power. The power system is an alternative to the standard electric option.

The crusher is V-belt driven and features a P.T. Tech clutch, which decreases power loss and increases fuel efficiency. An optional vibrating feeder with a tipping grid can be powered by the sidewinder via a variable frequency drive and remote control. The machine incorporates a 5-foot-by-16-foot Cedarapids horizontal screen box with a triple-shaft design for long life. IROCK also equipped the new Sidewinder with four hydraulic outriggers for quick plant set up.

Read More

Tags
Aggregates Equipment

Baldor Electric Company Introduces a New Line of High Performance Crusher Duty Motors

Baldor Electric Company has introduced a new line of crusher duty motors with improved reliability, performance and energy efficiency to help lower the operator’s total cost of ownership. With higher breakdown and locked rotor torque performance, Baldor Reliance crusher duty motors meet the demands of the toughest crushing applications worldwide.

The crusher duty motor platform is available in frame sizes 180T – 449T and in the power range of 5 to 350 HP. The entire product line is available from stock and meets current Premium Efficiency energy standards as well as future efficiency standards outlined by the Integral Horsepower Rule, which goes into effect June 1, 2016.

Read More

Tags
Aggregates Equipment

Metso Introduces HP5 Cone Crusher At AGG1 2015

The new HP5 crusher delivers a higher output of finished product using the same amount of power.
The new HP5 crusher delivers a higher output of finished product using the same amount of power.

Metso, has introduced a new cone crusher to the global market at AGG1 2015. Metso designed the new HP5 with safety, simplicity and eco-efficiency in mind. Automatic settings, specialized maintenance tools, reduced emissions and energy-efficient motors are just a few of the improvements built into this new cone crusher.

The Nordberg HP5 follows the successful HP3, HP4 and HP6 as the fourth model in an all-new range of high-performance cone crushers. The design of new Nordberg HP5 leverages Metso’s 100+ years of crusher know-how and experience with more than 9,000 HP cone crushers in operation worldwide. The result is a crusher that delivers the perfect combination of efficient crushing action, optimal feed size, high performance and the lowest cost per ton.

Read More

Tags
Asphalt Equipment

Cat AP600F and AP655F Asphalt Pavers Feature Quick-Heating Screeds and Enhanced Technology

Intuitive, accessible technology and a quick-heating screed system, which increases production while reducing crew idle time, are key features of the new Cat AP600F and AP655F Pavers. The AP600F is a wheeled paver. The AP655F is a rubber track paver that is equipped the exclusive Mobil-Trac Undercarriage.The pavers come equipped with new screed platforms, available in vibratory only, or vibratory and tamper bars: the SE50 V, SE50 VT and SE60 V.

Several features help improve fuel economy while maintaining high performance levels. Engine performance is aided by the 173 hp (129 kW) Cat C4.4 ACERT engine, which meets U.S. EPA Tier 4 Final emissions standards.

Read More

Tags
Asphalt Equipment

Volvo to Launch Intelligent Compaction System with Real-Time Asphalt Density Calculation

The industry’s first-ever real-time density mapping technology from Volvo Construction Equipment will revolutionize paving by eliminating guesswork, improving quality and increasing productivity.

Volvo Construction Equipment will soon introduce the Volvo Intelligent Compaction (IC) for select Volvo asphalt compactors available in two packages — Volvo IC and Volvo IC with Density Direct. In addition to offering the pass mapping, temperature mapping and data storage features of the Volvo IC system, Volvo IC with Density Direct includes the industry’s first real-time density mapping technology.

Read More

Tags
Asphalt Equipment

Atlas Copco Introduces new F1000T Tier 4 Final Paver

Atlas Copco’s Dynapac F1000T paver features exclusive technology that makes asphalt paving efficient and comfortable for the operator, such as ergonomically designed controls and Dynapac’s feed-control system.
Atlas Copco’s Dynapac F1000T paver features exclusive technology that makes asphalt paving efficient and comfortable for the operator, such as ergonomically designed controls and Dynapac’s feed-control system.

The F1000T tracked paver meets Tier 4 Final standards and increases productivity through operator comfort and visibility. The paver eliminates segregation with Atlas Copco’s exclusive feed-control system and features 18-inch-wide, smooth or treaded, rubber track bands that create the friction needed to push fully loaded pavers up steep inclines.

Read More