As regional airports across Australia undergo capacity upgrades, SAMI Bitumen’s Iulian Man talks to Roads & Infrastructure about the structural requirements of airport-grade asphalt.
In recent decades, the “airport” has shifted from a functional government asset into something more consumer-facing, sophisticated and business-orientated.
Highly trafficked international airports located in economic hubs such as Heathrow in London and Changi in Singapore are leading this charge. That said, as populations and economic centres shift, and concepts of multi-city metropolises gain traction, airports in regional centres are adapting as well.
In parallel, the Federal Government’s Regional Airport Program outlaid $100 million over four years in 2019 to support essential works, aviation safety and community access in growing regional towns.
lulian Man, SAMI Bitumen Technologies Technical Services Manager, has noticed a significant uptake in regional airport projects over the past five years.
He notes that in 2019 alone, SAMI’s SAMIfalt B380 binder was applied at three regional Western Australian airports: Wodgina’s Mineral Resources Limited Aerodrome, Duketon Airport and Port Hedland International Airport.
The Port Hedland upgrade was particularly notable, he says, with the upgrade playing a central role in Port Hedland’s strategic 2018-28 growth plan. As the second largest town in the Pilbara region, Port Hedland has an urban population of 14,320. While minuscule compared to Perth’s 2.14 million, the region is growing: its port, Pilbara Ports Authority, now functions as the largest bulk export port in the country.
“In line with expected population growth and increased air traffic volume, works on Port Hedland’s $40 million airport upgrade included a high-strength asphalt overlay and the construction of a new taxiway and terminal building,” Mr. Man says.
He adds that airport officials wanted to ensure large freight aircraft could continue to touch down at the site.
“While the terminal building was left to suitable ‘building’ contractors, Port Hedland engaged Boral to supply asphalt for the overlay and new taxiway. Boral then engaged SAMI to supply the binders.”
The project was a success, says Boral’s Technical Manager Asphalt & Quarries Emanuel Popescu, with SAMI’s polymer-modified binder (PMB) indicating significant deformation and groove closure resistance.
“Runways need to be grooved for improved surface texture when landing in wet weather to avoid the aquaplaning. Over time, those grooves are susceptible to close due to high stress aircraft traffic. It’s important to prevent those closures with high-quality binders like SAMIfalt B380.”
Mr. Popescu adds that Port Hedland is situated more than 1600 kilometres from Perth, which requires two days of transport.
“SAMI advised that we could store B380 for longer than other products if the temperature of the binder is reduced during the transport, which is an added time and cost benefit,” he says.
“SAMI are our principal supplier for all types of PMB in Western Australia. Specifically for this project, SAMI provided permanent technical assistance, with one of their lab technicians relocated to our mobile lab at Port Hedland.”
Mr. Man highlights a company-wide understanding of the engineering properties required to support intense aircraft traffic and the significance of high rutting and fatigue resistance.
“Historically, high-performance binders for airports were elastomeric, with a high level of polymer modification such as A10E,” he explains.
“While these generally performed well, the binder characteristics were not optimised to simultaneously address performance, cost-effectiveness, handling, logistical and ease of workability issues. So, we endeavoured to develop a binder that would.”
After several years of research, and a trial at Sydney Airport – concluding with an asphalt overlay at Broome International Airport in 2013 – SAMI developed the SAMIfalt B380.
“The newly developed binder was required to deliver good asphalt mixture stiffness, and higher resistance to viscous deformation such as groove closure,” Mr Man says.
“Given airport works are generally conducted at night, the asphalt was also required to mix without excessively high temperatures, and at moderately thin 50-to-60 millimetres layers.”
To meet these application requirements, SAMI designed SAMIfalt B380 via a composite polymer system that ensures stiffness and fatigue properties are managed.
Mr. Man says SAMIfalt B380 is recommended for use in all dense grade asphalt, stone mastic asphalt and open grade asphalt mixes.
“SAMIfalt B380 was developed by blending specialty polymers with harder grade bitumen, meaning it provides a combination of durability benefits to the asphalt. These significantly improve the performance and life expectancy of the mix,” he adds.
Another factor taken into account when developing SAMIfalt B380, Mr. Man says, is that airports are situated all over Australia – often at considerable distances from binder manufacturing plants.
“There have been problems with airports and the stability of PMB during transportation and storage in the past. A 2012 Austroads study on segregation and degradation in commercial styrene-butadiene-styrene binders, for example, found five out of 12 randomly selected binders segregated or degraded during transport. This raised concerns as those properties could lead to field and specification difficulties,” Mr. Man says.
SAMIfalt B380’s composite polymer characteristics circumnavigate this problem, he says, allowing the binder to be transported and stored for lengthy periods at its utilisation temperature, without any risk to the binder properties.
“Additionally, unlike other PMBs, SAMIfalt B380 is not susceptible to phase separation during storage. It also doesn’t fume during manufacturing, laying or compaction, offering an environmentally sound alternative to traditional asphalt binders,” Mr. Man says.
Furthermore, Mr. Man says the base course of airport asphalt has to be stiff enough to withstand high loading stresses, while the wearing course needs to resist plastic deformation. He adds that as such, a high-modulus asphalt containing SAMIfalt EME bitumen is recommended.
“Having already established itself in the airport market with a series of projects, such as Sydney Airport, Broome Airport, Kununurra, Coffs Harbour, and the three recent projects in WA, SAMIfalt B380 is increasingly becoming a binder of choice for airport projects around Australia.”