A new impact crusher is keeping a western Ontario aggregates producer in the black as it processes 1-in.-minus reclaimed asphalt pavement (RAP) particles from chunks as big as a coffee table, with the help of the right excavator.
AAROC Aggregates‘ processed RAP – originating from driveways and parking lots, in addition to cold milling machines – is destined for use as fill and for top dressings for low-volume pavements and parking lots. Asphalt millings from pavements are kept separately for use in spec asphalt mixes for local road agencies.
“The biggest challenge we have is uncertainty and variability of the product in our production environment,” says Jamie Martelle, sales and operations manager of AAROC, whose company selected an MR 130 ZS EVO impactor from Kleemann. “Not every site is the same. Not all feed materials are the same. One of the reasons we chose this mobile crusher was its versatility in being able to adapt to site conditions.
“For example, we get positive production in tight quarters.”
To maintain consistency of end product, AAROC separates incoming asphalt from commercial projects from incoming highway pavements.
“Asphalt is softer than concrete, so it doesn’t take much to break it down,” Martelle says. “Nonetheless, we will get better production from asphalt-milled product than slab product. That’s why we control the raw material as it comes in. We know the customers and what they provide. As long as we have the room to keep the stockpiles separate, we can maintain composition.”
Depending on the location, AAROC produces a 5/8-in.-minus RAP for spec asphalt mixes in addition to its 1-in.-minus RAP.
AAROC, which is a unit of the John Aarts Group of Ilderton, Ontario, Canada, moves the crusher from aggregates site to aggregates site. The company also has the option to move the crusher to construction sites where demolition concrete or asphalt sits to be recycled.
RAP was recently processed at the Westcliff Pit, one of five locations in Ontario that AAROC manages. AAROC crushed RAP pieces there at a rate of 330 to 358 tph.
Tom Ritchie, AAROC’s crusher foreman, says this is an adequate speed.
“Anything more than that will make it hard to keep up with the excavator,” he says.
Finding the right excavator to feed raw material proved to be a challenge, Ritchie adds.
AAROC has had its new Mobirex MR 130 ZS EVO impactor, which features a 52-in. crusher inlet width, since January 2014. But the company first tested the waters with an MR 110 ZS EVO that featured a 44-in. crusher inlet width.
“We fed the MR 110 with a smaller excavator,” Ritchie says. “We started off with the MR 130 using a like-sized excavator, but we were struggling to keep up with the asphalt.”
Breakout force was lacking, he says, because reclaimed asphalt gets packed in hard and melds together in the sun. Trucks and excavators run over the reclaimed asphalt, too.
AAROC now feeds the MR 130 ZS EVO with a 2.75-cu.-yd. bucket that’s 54 in. wide.
Prescreen for productivity
An integral, double-deck, independent prescreen below the receiving hopper improves RAP productivity and profitability for AAROC. The denotation “Z” in the nomenclature of the Kleemann MR 130 ZS EVO indicates the presence of the prescreen, which utilizes an elliptical motion instead of a vibratory linear motion.
The benefit is more product emerges from the prescreen much cleaner, with smaller material bypassing the crushing circuit or going to the side belt as a salable product, increasing total output and reducing long-term wear costs.
“It lessens the load on the crusher itself,” Ritchie says. “It lets the fines pass through so they are not fed into the crusher, causing needless wear. It lightens the load overall. The fines drop through, join the crushed material where they are sized in the attached final screen, and oversize is returned to the crusher circuit.”
With its continuous feed system (CFS), each step the material goes through in AAROC’s plant is wider than the width of the one before it, eliminating choke or wear points.
The crusher is diesel direct-driven via a fluid coupler, and feedback is provided from the engine to the controlling computer, allowing indications that the crusher may be getting overloaded. CFS manages a more equal loading of the crushing area, in which the conveying frequencies of the feeder trough and prescreen are adapted independently of each other to the level of the crusher, thus significantly boosting performance.
“It lets the system know when it’s getting overloaded and will slow down the feed so it doesn’t stall the crusher out,” Ritchie says. “It’s a very valuable feature that saves us a lot of digging.”
At the same time the exclusive CFS maintains a choke feed to the crusher, eliminating stops and starts of the feed system, improving production, material shape and wear.
Staying mobile
The MR 130 ZS EVO impactor from Kleemann is the largest crusher AAROC could obtain that would still fit on its flatbed trailers.
“Our machine is completely portable,” Ritchie says. “We move it as we need it around our pit locations. Any of them may have a need to crush concrete or asphalt, or a customer may request us to come and crush.”
Moving the crusher is the easy part, Ritchie adds.
“The worst part is cleaning it off. We take any stones off the machine and wipe it down, getting it as clean as we can.”
This varies from the existing plant it replaced – a primary crusher with a screen alongside it that would recirculate the oversize back to the primary crusher. Yet, on the new plant, the screen is self-contained, attached to the loading conveyor and completely eliminates the standalone screen.
“The attached final screen was a major factor in our selection,” Martelle says. “No matter what we are doing, every second we run that machine we are saving money.”
The impactor is easy to set up, Ritchie adds.
“With the old plant of crusher and screen, it would take three days to tear down and move, with a lot of labor,” he says. “But with this model, we can have it broken down and cleaned in four to five hours, and that’s from the time you stop feeding it to the time your are ready to load on the lowboy.”
The new mobile impact crusher’s attached final screen is the biggest screen AAROC could get to fit on its lowboy and still move it around, Ritchie says.
“That’s due to weight restrictions, height and width,” he says. “The final screen stays on, but we have to lower the side conveyor and fold the hydraulic hopper sides down, which is easy to do. You can’t beat it.”
AAROC is also accruing savings in fuel consumption, according to Martelle.
“We’re seeing a 30 to 35 percent reduction in fuel costs with the new impact crusher,” he says. “It has much to do with the diesel-electric direct drive, as opposed to a hydraulic drive.”
Ritchie’s handheld remote control allows him to operate the crusher from within the feeding excavator cab, or control its movement as he walks alongside it, guiding the impact crusher onto the flatbed trailer.
“The remote controls feeder speed, magnet belt and the tracks,” Ritchie says. “It also raises and lowers the jam door on top of the apron lid. If you get a big piece in the hopper, you can raise the door and keep the flow going.”
The versatility and quick mobilization of the impact crusher has allowed AAROC to service all of its locations’ market demands.
“If we had our old setup, we would be well behind on our production targets due to lost time of mobilization,” Martelle says. “Because we can move the Kleemann in the morning and be running it the same day across town or 30 miles away, we can crush another day and a half more than we could before.”
Tom Kuennen is a freelance writer specializing in the construction, energy and mining fields. Visit his website at www.expresswaysonline.com.