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
Asphalt Equipment

Keeping rising costs in check

An asphalt producer found himself in a situation faced by too many asphalt manufacturers. “The cost of aggregate continued going up,” said Francois Guilbeault who, with his brother, owns Asphalte Drummond Inc., based in Drummondville, Quebec. “It was having an impact on our business.”

In theory, some of the cost could be passed to customers, though that is not a business approach Asphalte Drummond likes to take. Customers don’t appreciate rising prices, and Guilbeault doesn’t want them searching for lower-cost alternatives. Yet surrendering profit margin is not a healthy business approach, either. “We had to find a way to control the costs, while not hurting our business,” Guilbeault said. He believes others in the industry face similar challenges.

Read More

Tags
Aggregates Equipment

Sandvik Construction Mobile Crushers and Screens Hosted Their Inaugural Global Distributor Conference with 75 People from Almost 50 Distributors Worldwide Taking Part.

The programme of events took place from 12th – 15th January and consisted of an agenda of keynote sessions and workshops held at the Slieve Russell hotel in Ireland followed by an impressive product display at their new Centre of Excellence in Ballygawley, Northern Ireland.

The event provided the opportunity to bring together their global network of experienced distributors to discuss key areas of business growth in 2015 and to ensure that the preferences and requirements of their global customer base continue to be met and exceeded.

Read More

Tags
Aggregates Equipment

Terex Finlay Introduces New J-1170 Primary Mobile Jaw Crusher

The NEW Terex Finlay J-1170AS is a high performance primary mobile jaw crusher built around the renowned and aggressive Terex 1100mm x 700mm (44” x 28”) jaw crusher, with a proven track record in recycling, aggregate production and mining applications. A key new feature of this model is the on-board detachable sizing screen

The Terex 1100mm x 700mm (44” x 28”) jaw chamber provides excellent material reduction and product sizing in the processing of blasted quarry rock and ore material. The jaw chamber is also available with optional hydraulic release, an excellent feature when crushing construction and demolition debris. The hydraulic release option has an automatic overload protection system to prevent damage by uncrushable items in the feed material.

Read More

Tags
Aggregates Equipment

Sandvik Construction to Show Impressive Lineup Agg1

Sandvik Construction will be taking the opportunity of AGG1 to launch the Dino DC400Ri surface drill, while at the same time displaying its QS331 mobile cone crusher, Bretec breakers and tooling offering.

The Dino DC400Ri is a hydraulic, self-propelled, self-contained, crawler based surface drilling unit with full radio remote control operation for 51 – 76 mm hole sizes. It offers top drilling performance with a new RD414 rock drill, a robust boom that has the largest coverage area of its size, a patented collaring guide and an economical Tier4 Final engine. Due to its versatility the Dino DC400Ri is the perfect machine for drilling and blasting contractors, but suitable also for quarries and the municipal sector. Its typical applications consist of road construction, demolition works, secondary breaking, foundation drilling and trenching.

Read More

Join our mailing list

Latest headlines
delivered to you weekly

Heavy Equipment Guide
Tags
Asphalt Equipment

Neal Manufacturing Upgrades DA-350 Sealcoating Machine to Increase Productivity and Ease of Use

Neal Manufacturing, an industry pioneer in asphalt sealcoating equipment, upgraded its DA-350 Dual Applicator sealcoating machine to enhance productivity and ease of use. The three-wheeled, self-propelled unit has a 350-gallon tank and allows contractors to apply sealcoat with squeegee and spray systems.

Neal added a high-powered blower to the front of the DA-350 to help users quickly and easily prepare the surface for sealcoat application. The blower produces more than 6,000 cfm, triple the output of a typical walk-behind blower, for fast and thorough dirt and debris clearing. The blower unit rotates, allowing contractors to lock it in an upright position for transportation or move it down for operation. The nozzle on the blower articulates 360 degrees enabling the contractor to blow debris in the optimum direction. Once the blower cleans the area, a 40-gallon fogger system cools surfaces prior to application to ensure optimal adhesion.

Read More

Tags
Asphalt Equipment

Bergkamp’s New MA30 Applies Mastic Surface Treatment to Preserve Asphalt Pavement

Bergkamp Inc., is introducing the MA30 Frictional Mastic Surface Treatment Applicator that allows contractors and government agencies to apply Frictional Mastic Surface Treatment over highways, roads, parking lots and airport runways to protect the surface and extend the life of the pavement. It applies a material mix that is made to precise specification, which results in fewer operator calculations and on-the-job adjustments, minimizing operator training time. The full-length ribbon mixer works to maintain the proper material consistency, regardless of the truck engine speed during transport to the job site. The Frictional Mastic Surface Treatment is then applied over the existing pavement through a variable width, low pressure spray bar that has side-shift capabilities.

Frictional Mastic Surface Treatment is a mixture of asphalt emulsion, increased levels of angular fine aggregates, recycled materials, polymers and catalysts. The purpose of Frictional Mastic Surface Treatment is to minimize future maintenance treatments and get traffic back on the pavement more quickly.

Read More

Tags
Aggregates Equipment

McCloskey International’s New J Series Crushers Set to Debut in North America at AGG1

AGG1 visitors will get a first look at  McCloskey International’s new jaw crusher, the J45, in Baltimore, Maryland March 17-19, 2015. On display at Booth 1064, the J45’s true 45" x 27" jaw, with both level and load sensors, ensures the most efficient material handling across applications. The new model joins the redesigned V2 Series jaw crushers coming to the market, including the J40 V2 and the J50 V2.

Also being introduced is the J45R, which allows operators to produce a crushed and screened final product with one machine. Like the J45, the J45R boasts a 14’-10.2” x 7’-3/4” hopper with close to 9 cubic yards (6.8m3) capacity. The 5’ x10’ Screenbox features McCloskey “High Energy” technology, with adjustable speed. Rugged and versatile, both models have undergone rigorous field-testing to ensure the reliability required for the toughest projects around the globe.

Read More

Tags
Aggregates Equipment

New Terex Cedarapids CRS620S Screen Plant Handles Wider Range of Applications and More Capacity

Terex Minerals Processing Systems (Terex MPS) has expanded their CR Series portable plant line with the addition of the Terex Cedarapids CRS620S screen plant.

The revolutionary plant features the next generation, patent pending LJ-TSV screen. The new screen increases production and handles applications not possible with traditional horizontal screens because it combines the legendary El-Jay high g-force oval stroke motion with adjustable slope operation. This plant can handle larger deck loads and larger screen openings. Hydraulics quickly change the screen slope in 2.5° increments up to a maximum of 7.5° to best fit the application. Screen openings up to 6” (152mm) are possible. Patent pending “slant spring” screen suspension provides stability at all slopes. The plant utilizes large capacity conveyors to handle the high production capabilities of the new LJ-TSV screen. The 48” (1219mm) wide fines conveyor with its elevated discharge and the two 30” (762mm) wide reversible cross conveyors which extend up to 42” (1067mm) beyond the main frame, easily feed off-plant conveyors. Roll-away blending chutes and extended walkways allow easy access to screen cloth. The patented low-maintenance flex shaft screen drive eliminates drive belt influence on the screen motion, belt whip, belt slippage, and spring loaded belt tensioners. There are no drive adjustments necessary when the screen slope is altered. In addition, the new flex shaft drive folds for travel, without shaft disassembly, to minimize plant transport width.

Read More

Tags
Aggregates Equipment

Reducing Costs, Improving Economic Sustainability and Process in the Quarry Industry

Dyno Nobel, a global leader in commercial explosives, along with Sandvik Construction, a business area within the Sandvik Group providing solutions for virtually any construction industry application, once again teamed up to put on the 9th annual Quarry Academy in San Antonio, Texas. Demand for the academy surpassed any previous year with classes filling up in just a few weeks of registration. Those who were able to attend experienced another highly successful educational seminar.

Over 125 people participated in workshops to learn the latest developments in quarrying, safety, lean processes and total value in cost reduction and economic sustainability. This three-day event took place over November 18–20 and included a tour of the CEMEX Balcones Quarry, the biggest quarry in the US (according to USGS data). The tour included a visit to the water treatment plant, an electronic initiation system demonstration, a production blast, seismic and post blast overview and ended with a field survey control including instruments, tools and methods.

Read More