The Australian Bureau of Meteorology found that 2019 was Australia’s warmest year on record, with the national mean temperature for the year placed at 1.52 degrees Celsius above average.
Climate predictions, by the CSIRO and the Australian Government, show that this increasing trend will continue for the rest of the century. Across four major clusters, estimations show that later in the century if a high emissions scenario becomes reality, the country could see from 2.7 up to 5.3 degrees Celsius of warming.
Warming of this nature pose challenges to the road building industry. It must adapt to develop asphalt mixes that can perform under increasing temperature conditions and with increase of channelised loading expected on road surfaces with the concomitant evolution of autonomous vehicle technology.
Since its establishment more than 40 years ago, SAMI Bitumen Technologies has been continuously developing bituminous binders in order to cater to a wide range of traffic and climate conditions.
It’s latest new generation hybrid binder, SAMIfalt I-Brid, was developed as a result of substantial research work led by Kanjana Yindee, National Laboratory and R&D Manager SAMI Bitumen Technologies. This was in partnership with Royal Melbourne Institute of Technology (RMIT), one of the leading universities in Australia for asphalt and bitumen technology.
Iulian Man, SAMI Bitumen Technologies Technical Services Manager, says the binder displays excellent performance over a wide range of service temperatures.
“You can use this product in very hot climates, especially in northern Australia but also in cooler climates such as Victoria or Tasmania,” Mr. Man says.
He says under hot ambient conditions the wearing course of pavements tend to soften up and therefore there is a need for a bituminous binder that would impart deformation resistance under heavy traffic loading.
“In contrast, in cooler areas, as the pavement has a tendency to stiffen up under low temperature conditions, cracking may be a problem and therefore the binder used in the wearing course needs to be flexible and resilient” Mr. Man says.
“With I-Brid we are able to cover a very wide range of service conditions when it comes to ambient temperatures, with the binder imparting rutting resistance at high service temperatures and cracking resistance at low and intermediate temperatures.”
Essentially, the binder is a combination of innovative plastomeric and elastomeric polymers and the development team started working on the product concept around 18 months ago.
Filippo Giustozzi, Senior Lecturer, Civil and Infrastructure Engineering RMIT, worked alongside SAMI to test and create I-Brid.
He says at the very beginning the team had to identify innovative polymer groups that were also able to be mass produced, in order to cater to the large quantities needed for asphalt applications.
“In the beginning we looked at each single polymer, to determine their single actions. The second task was then to put them together and understand the compatibility of each of the polymers and their cross-linking abilities,” Dr. Giustozzi says.
“The four polymeric pillars in I-Brid are very specific because they need to get on well with bitumen, which is not easy to deal with because its behaviour varies a lot with temperature and with frequency of loading.”
The challenge when combining the polymers was to ensure the mix created was stable and could be easily handled by any section of the road construction chain without any significant change from current products.
“We overcame this with a lot of chemo-rheological testing using different temperatures and frequencies of loading. There was a really broad range of tests and the process took almost two years,” Dr. Giustozzi says.
He says once the correct polymers were found for the hybrid binder, each hybrid was tested alone, and the team tested around 60 different hybrid combinations.
“Rheological testing was performed on the hybrid binders, and this was good because we could easily change the temperature and frequency of loading. We tested from 0-5 degrees all the way up to 90-95 degrees Celsius,” Dr. Giustozzi says.
“That is the beauty of this binder because we didn’t want it to just be good at high temperatures, we wanted the binder to also be very good at a very high temperature while providing low stiffness at 25 degrees Celsius,” he explains.
In phase two the team also conducted significant performance testing on asphalt mixes produced with the I-Brid binder which included, fatigue tests, rutting tests with a wheel tracking machine to test for moisture damage and fuel resistance tests.
He says the team ensured that the asphalt was tested across the full spectrum of temperatures under which the asphalt was expected to perform in the field at each stage of the process.
Mr. Man says I-Brid was originally developed specifically for airport applications. As a result, the binder had to adhere to the strict requirements for these projects due to the liabilities and risks associated with airport operations and aircraft movement.
“We have to ensure that the mix containing SAMIfalt I-Brid fully conforms with the stringent airport specifications. Airports will usually have particular contract specifications that the contractor must abide by and we had to ensure those could be always met,” he says.
The first application of SAMIfalt I-Brid will be performed at the Bundaberg Airport in Queensland and laid by Colas Queensland. The binder will be laid on the airport’s apron which Mr. Man describes as a car park for aircraft.
“The binder displays a very high level of deformation resistance meaning it’s sturdy and should perform very well in terms of ability to take stationary loading,” he says.
“Bundaberg Airport’s apron is a starting point for this binder, and I’m convinced that due to its exceptional properties it will become well known in the industry and its use will significantly increase,” he says.
Dr. Giustozzi believes this binder could also have a huge impact on the road construction industry for use in high traffic areas, such as highways and busy intersections.
“Whenever you have a high demand road and you have fatigue and rutting, people are looking for both flexibility and high-temperature resistance at the same time, a ‘universal’ binder. In all of these applications I think the I-Brid is the right solution,” Dr. Giustozzi says.
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