It’s been a mainstay of the Australian pavement and aggregate recycling sector for over a decade. Now, Astec’s portable crushing and screening plant has gone through a makeover for Australian conditions, with benefits for both owners and the environment.
The portable ProSizer plant by Astec is no stranger to the Australian construction landscape. It has been recycling aggregates and asphalt solutions here for more than a decade. The ProSizer has also been applied in the pavement recycling sector, where it is used by road profilers and asphalt producers to process reclaimed asphalt pavements (RAP).
The ProSizer – named for its “product sizer” application – incorporates a horizontal shaft impact crusher and screen on a portable chassis and trailer. Traditionally, the ProSizer has been available in three models – the ProSizer 3100, 3600 and 4200. The average dimensions of each of these models is around 20.4m x 3.4m.
Last year, Astec Australia launched a compact version, the ProSizer 2514MF. At only 17.56 metres, the 2514MF is almost three metres shorter than its predecessors. As Astec Australia Business Line Manager – Materials Solutions Adam Gordon explains, the redesign was part of Astec’s strategy to make the plant more easily transportable across every state and territory.
“The new Astec ProSizer is a result of collaboration between the Astec Australia team and the manufacturing team in the US, taking in feedback from our clients and also factoring in considerations for Australia’s road transport regulations,” Gordon tells Roads & Infrastructure.
“The original ProSizer was a good machine and is still suitable for the US market. But over the years, there have been more regulations imposed by different states in Australia, which made it difficult to tow the plant cross-country. With many kilometres of spray sealed roads in Australia, we identified an additional benefit by minimising the overall trailer length to reduce any potential risk of damaging the sprayed seal surface when turning sharply. For all these reasons, we knew it was time for a redesign,” he adds.
Higher productivity
For the pavement recycling industry, in particular, the 2514MF delivers benefits. As Jorge Boil, Astec Australia’s Business Line Manager – Infrastructure points out, the more compact design allows smaller asphalt producers to increase their economic returns by transporting the ProSizer from one project site to another.
“A big problem with having a fixed plant is volume. Because the 2514MF is easily relocated, it can work across multiple sites, producing the required volumes at each location. For producers, that flexibility means a much better financial return on their investment,” Boil explains.
This control over processing capacity becomes more critical when considering the nature of recycled asphalt, Boil adds.
“With RAP material, particularly in summer, if you process and screen the asphalt-coated aggregate and store it outdoors, it can harden due to heat and a crust forms on the outside. To avoid creating a lumped stockpile, producers need just enough material processed so they don’t run out, but not so much that they have to re-process it. The ProSizer 2514MF gives them that control.”
With the ProSizer, the reclaimed asphalt is put through an optimum amount of impact to break the asphalt matrix, leaving the asphalt coating on the aggregate intact. This in turn reduces the need for introducing virgin asphalt to the mix, ensuring the recycled material delivers maximum value, Gordon explains.
“When you dig up road material, there’s a lot of variable materials present. The goal for us in designing the ProSizer has been to maximise the quality of the recycled material, by retaining the asphalt component as binder, and also by removing unwanted components such as metal and geofabrics from the mix.”
As well as benefits in efficiency and transportability, the ProSizer 2514MF delivers other features in terms of efficiency, ease of maintenance and environmental impact.
ProSizer 2514MF benefits
The first design change is the rotated feed bin. On the new model, the feeder bin has been rotated 90-degrees. This means the feeder retains the same five cubic metres capacity while the overall length of the bin and the conveyor is reduced by about two metres. Replacing the standard, high frequency screen with a 2514 multi-frequency inclined screen – which is where the model also takes its name from – is another key innovation. Gordon says the new screen design also saved on overall length.
“The original plant had a high frequency screen where we exited the screen media by introducing a vibration. But for that vibration to happen, the box had to be at a very steep 43-degree angle so gravity would cause the material to run down. By lowering the discharge point, we were able to reduce the conveyor’s angle to 22 degrees which, in turn, helped reduce the gap between the screen and the feeder.
“Also, in the multi-frequency model, the whole screen box is moving, and we have introduced another vibration into the bottom deck,” he says.
In addition, the preferred screen media is stainless steel to minimise adhesion between warm asphalt and the screen media surface.
“When you are crushing and processing asphalt, it gets warm and as a result it gets tacky and sticky. By introducing the extra vibration, and also using stainless-steel screen media, which has very low coefficient of friction, asphalt-coated aggregates can slide through more easily.”
The 2514MF ProSizer is also better equipped to filter out unwanted material such as geofabrics and metal particles from the recycled material, Gordon explains.
“A lot of the roads that were spray sealed in the 70s and the 80s have a layer of geofabric to improve adhesion between the road base and the sprayed seal. That’s good for the road, but not so much for the recycling. We have added a hydraulic valve, which can also be controlled remotely as an option. The valve can move the returns conveyor away from the closed circuit, discharging the geofabric and petromatt out of the system and into a bin,” he says. “Also, when you recycle roads, there are always steel wires and cast-iron bits and pieces that get mixed into it. No crusher likes steel going through it. That’s where the self-cleaning magnet on the conveyor comes in and helps get rid of the unwanted material.”
The new Astec ProSizer features a Cummins Tier IV diesel/hydraulic engine – an upgrade on the previously Tier III engine – resulting in reduced emissions from the plant.
From a maintenance perspective, the addition of an auto-greasing system for all lube points, and a radiator pre-filter system to minimise build-up on the cooling system, helps keep maintenance down. Also, the radiator package has been designed so it can be swung open perpendicular to the chassis for easier access to the engine and more convenient cleaning of the radiators.
Gordon says the first Astec 2514MF ProSizer has arrived in Australia, and he sees scope for the new model to be adopted in other countries such as in New Zealand, which has similar road conditions to Australia.
“If you have a machine that helps you maximise your recycling and screening output, minimise use of virgin material for asphalt production, reduce emissions and also saves on disposal costs, that’s a win-win-win-win scenario,” he says.
“We are very proud of the work done by the Astec Australia team in incorporating feedback from our clients and working in close collaboration with the global manufacturing team. With the compact design of the mobile screening plant, the unit can fit into a single-load trailer and be easily moved around anywhere in Australia, with the result being greater efficiencies and economic outcomes for our clients.”
This article was originally published in the April edition of our magazine. To read the magazine, click here.
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