Airport pavement research ready for takeoff

By the early 1990s, the administration of Australia’s major airports was passing from government to the private sector, a move that has subsequently seen Australia’s airport infrastructure assets change in a variety of ways.

What hasn’t changed, argues Dr. Greg White from the University of the Sunshine Coast, is the research, design and practice behind the nation’s airport pavements.

“Airport privatisation has been great for a number of reasons in the airport industry, but research, design and innovation in technology has been overlooked,” he says.

“I think when the government privatised Australia’s major airports they must have simply forgotten about the technical aspects of the pavements.”

The lack of advancement within the airport pavement technology and innovation space, he says, has created a gap in knowledge, whereby Australia’s airport infrastructure is falling behind in the greater infrastructure sphere.

As each major Australian airport is now privately owned, Dr. White says there has been little coordinated advancement in runway construction and maintenance in recent decades, despite broad innovations in pavement design, materials and technologies, as well as significant changes in aircraft.

“Different engineers within the airport companies have been frustrated for more than 20 years, as we’re doing things the way they have been done since the 70s. There are advancements happening internationally that we can learn from and collaborate on,” Dr. White explains.

Coming from an airport pavement engineering background, Dr. White over the years has identified these limitations within this part of the airport sector as a result.

“I’ve worked for the RAAF as an airfield engineer, as well as for a number of consultants and most recently a construction company in this area. From practicing this kind of work for nearly 20 years, I’ve learnt about new technologies along the way, particularly in road construction, and thought: we could be doing these sorts of things in airport infrastructure,” Dr. White explains.

Not only were the opportunities there to transfer knowledge from roads to airports, but so was the proof – in many instances it wouldn’t be the case of reinventing the wheel.

“I started exploring this further out of interest, but I wasn’t able to take it further by myself,” he adds.

Dr. White commenced a PhD on aircraft-induced shear stresses and their impact on asphalt runway surfaces at the University of the Sunshine Coast, graduating in 2015.

During this time, Dr. White’s research caught the eye of industry, whereby the idea of reinvigorating the design and construction of Australia’s airport pavements began gaining further traction.

“Over the course of my PhD, both Australian Airports Association and Australian Asphalt Pavement Association came to us and ask how they were able to have access to the kind of information I was gathering, and that sowed the seeds,” he says.

With industry interest, Dr. White began seeking ways to undertake a collaborative and practical research program into airport pavements and advancing the sector.

“Pavements are a small part of the airport industry – it’s not that big, and airport pavements are really small part of pavement industry. Privately owned airports can do this kind of research themselves, but there are more benefits if they could all chip in to finance research collaboratively,” he says.

“Without industry support or validation, the university couldn’t support the research we wanted to do. They asked us to gather support from the airport operators in just under a year, which was probably one of our biggest challenges. People don’t want to support something without proof of it working, so it took a few leaps of faith.”

Those leaps of faith were enough, however.

With Dr. White successfully meeting the goals set by the university, it announced the launch of a $2.85 million collaborative five-year research program this past November, aimed at advancing airport pavement technologies and practices around Australia.

The program is a partnership between the university, Australian Airports Association, Department of Defence, Perth Airport and Sunshine Coast Council, which owns Sunshine Coast Airport. Dr. White is also the program’s Director.

“This is the first nationally funded, coordinated research program into airport pavements since Australia’s major airports were privatised in the 1990s,” Dr. White says.

“Our goal is to update technologies and practices to make runway surfaces last longer and incorporate global airport industry and national road engineering innovations into Australian airport pavements.”

He says the program team expects to see early outcomes in areas such as advanced test methods for bitumen and asphalt materials, non-destructive testing for runway strength rating, surface preservation material evaluation and methods for comparing the costs and benefits of concrete and asphalt runways.

“One of the first things we’ve recently completed is the design of a performance-based specification for runway surfaces,” Dr. White says.

“There are plans for the construction of five new runways across Australia in the next decade – including one on the Sunshine Coast – so it’s a great time to undertake this research and support its implementation at a number of major airport developments.”

Dr. White and the research team has already been involved in a number of airport projects where milestones have been achieved.

“We worked on the Whitsundays airport runway, which we call our ‘zero waste runway’,” he says. “In the normal scheme of things in airport pavement construction, we typically won’t reuse the pavement, but using reclaimed asphalt pavement or stabilisation and using existing pavement material generated virtually no waste. It made sense as it’s common in the road construction industry and the environmental benefits and cost savings were substantial.”

Dr. White estimates that using traditional runway design on the Whitsundays project would have sent around 11,280 tonnes of existing asphalt, 36,660 tonnes of existing natural gravel, 40,608 tonnes of excavated subgrade and 1354 tonnes of RAP to landfill. By utilising a design that fully recycled the content, the project sent zero tonnes of the above materials to landfill.

“The majority of the work isn’t inventing things from scratch, but looking around the world in Europe, the UK, the US and figuring out which of these things make sense for us and finding out where our industry can do it using our resources and in our environmental conditions,” Dr. White says.

He states that validated ideas – technology that has been successful implemented overseas and proved to be beneficial – are extremely valuable here too.

“Validated ideas are always translatable, and most of what we’re doing is adopted from what other people have done.”

Dr. White explains that technological developments in the road industry, for instance, have proved translatable to airports. However, there are still many aspects of airport pavements that complicate further advancement here.

“For airports, the pavement needs to be specifically made to deal with the impacts of aircraft, such as higher wheel loads and tyre pressures, not regular vehicular traffic,” he says.

“There are things common in design between roads and airport pavements, but airport pavements are designed for just planes, which are different to road vehicles and means some technical aspects are hard to transfer.

“Aeroplanes are top-heavy and have a close centre of gravity and runways are flat, which means they can pond water quite easily, so engineers need to be very careful around that. Planes can come in at 180 kilometres per hour, and when it rains the pavements have to be able to cope, and that’s an aspect of airport runways that cannot change.”

Dr. White says most airport runways, for instance, are grooved to prevent ponding, and cater for heavy aircraft landing at high velocity.

“Grooved pavement is something we don’t use anywhere else in a road environment. This prevents ponding and makes sure skid resistance is right for the aircraft. Aircraft also have low-hanging engines under the wings, which are very fragile, and loose material from the pavement can be ingested into the engine,” he adds.

The criteria to use grooved pavements on runways makes the transfer of knowledge from the road construction industry to the airport pavement sector tricky.

Dr. White says to even test a different methodology requires closing down a runway.

However, there are concepts out there already being employed internationally that the researchers want to investigate.

“We could look at alternative asphalt pavements that still achieve surface friction but aren’t grooved. There are some technologies established in Europe and China already, and we’re going through the process with Australian asphalt producers with the aim of trialing something in the second half of 2019,” he says.

“Removing the groove reduces airport runway costs significantly. Typically, resurfacing of an airport runway in Australia without grooves could save costs of $600,000. There are close to 100 major airports in Australia and not having to use grooved surfaces could result in significant cost savings – savings achieved without having to invent things from scratch.”

The obstacles ahead

The research program will employ several Masters and PhD students and postdoctoral researchers. However, this poses one of three major challenges ahead Dr. White identifies for the research program.

“A lot of the projects we’re involved in lend themselves to a post-graduate PhD or Masters students, but it can be hard to find people who are interested in this particular section of the pavement engineering sector,” he says.

Another major obstacle Dr. White says the program faces is obtaining real data and contributions from the industry, whether asphalt or concrete-related.

“Some parts of industry have embraced that and are being really supportive and doing their own testing on site and in their own labs. But, we need lots more aspects of industry to embrace it and help add to the information being gathered out there.”

Thirdly, he says “the proof is in the pudding” – industry and airport owners want to see real-world outcomes before committing to anything new.

“The big airports with frequent international flights don’t want to put something down that hasn’t been done anywhere else. Altering the groove in airport pavements, for instance, means they have to close down the runway,” he says.

“State road authorities can trial new pavement technologies and methodologies on their expansive road networks and can afford to get it wrong the first few times until they get it right.

“But, airport companies typically own one airport and one runway. If you don’t get it right first time, you don’t stand a chance.”

While the challenges are evident, Dr. White says the program team is aiming to address and overcome these obstacles through spreading the message and getting further airports, industry stakeholders and businesses on board.

“We’re using the Australian Airport Association’s forums as our primary vehicle to talk about the research in an industry context, and we’ve got a number of sessions next April and May to get the message out there.”