It’s been a rocky road for an unusual asphalt compactor design that once showed clear signs of outperforming traditional compactors. The Ministry of Transportation Ontario had been very keen on the new compaction method, which uses a rubber track instead of a steel drum roller. But poor performance during official tests have derailed the initiative.
The compactor, called AMIR TRAK, is the creation of Abd El Halim, former professor at the Dept. of Civil and Environmental Engineering at Carleton University. The ministry (MTO) has worked with Halim, along with general contractor Tomlinson Group, to test the machine alongside traditional compactors. In trials each year since 2011, AMIR TRAK had consistently provided slightly better compaction results and much better permeability results than a traditional compactor.
“When I review asphalt compacted by the AMIR TRAK five, six or even seven years ago, it shows much less degradation then the side compacted with traditional compactors,” says Frank Pinder, area construction manager at MTO. “Less permeability leads to less road degradation.”
In August 2019, the MTO, along with Canadian industry associations, organized a demostration day to introduce the machine to contractors. Aside from a few small trials, it was the first public test of the AMIR TRAK’s rubber-tracked method.
“The current philosophy of compacting is a very high load over a small footprint; the drum comes into contact with the asphalt for just milliseconds,” explained Halim at the demo. “AMIR TRAK works the opposite; it uses a very low type of contact for a long time.”
Because the machine does not use vibration to achieve compaction, it can work on asphalt that is at lower temperatures than normal. And while a typical highway paving train includes three compactors and each compactor makes six to eight passes, AMIR TRAK has been shown to be able to achieve the same compaction results with just one machine in six to eight passes.
Halim had explored the rubber-tracked compaction method in academia for years before moving forward, partnering with Canada’s National Research Council to design a machine based on his technology. He published results of his machine and in 2011 the MTO tested it for the first time.
During the 2019 demo, Tomlinson Group used the AMIR TRAK to compact asphalt placed on a bridge, as well as a few hundred feet of the bridge’s approaches. But this time, the AMIR TRAK didn’t outperform the other compaction train—it didn’t even meet industry standards.
The poor results had experts familiar with the machine scratching their heads, since it had shown slightly higher compaction results and significantly higher permeability results in side-by-side trials in the past. A test strip had been successfully completed, with an average density and permeability of 94.2% and 0.39x10-3 cm/s, so there was disappointment with new compaction and permeability results of 89.5% and 2.04x10-3 cm/s on demo day. A review said possible reasons for the poor performance were insufficient tension on roller belts and roller speeds set too high.
Since then, momentum behind AMIR TRAK has flagged. Halim, who had been dealing with ongoing health issues, died unexpectedly in Sept. 2019. In May 2020, two AMIR TRAK rollers were tested again, but despite increased attention, the results—though improved—again fell short. The average compaction and permeability achieved was 91.5% and 0.186x10-3. Permeability improved, but compaction was only marginally acceptable, according to the MTO standard.
Today, the future of the rubber-tracked asphalt rollers is cloudy. Tomlinson Group owns the only two AMIR TRAK machines in existence, but to date it has slowed work with MTO to develop them further. The machine’s design is owned by the Halim family, and it is unlikely any new machines will be made soon. But for MTO’s Pinder, these mixed results only show that more work is needed, and MTO is still interested in developing the technology for full-scale deployments some day.