With an increasing need for alternatives to traditional railway line track construction, Boral has introduced a new and durable asphalt rail pavement construction product to the Australian market – Railpave.
Deloitte Australia’s 2017 Value of Rail report, commissioned by the Australasian Railway Association, finds that the rail sector has made significant contributions to the national economy and will play a significant role in catering for Australia’s growing population, which is forecast to double to almost 45 million people by 2070.
With major rail projects underway including the Melbourne Metro Tunnel, Sydney Metro and Inland Rail – not to mention the myriad regional rail upgrades and projects – given the contribution of the industry to the national economy, how Australia’s rail infrastructure is being delivered is becoming more important than ever.
Increased traffic loads and volumes, combined with concern for the environment and the concept of sustainability, are elements that have resulted in new required approaches to rail design, according to the European Asphalt Pavement Association’s Asphalt in Railway Tracks report.
The different properties of bitumen and asphalt, the report finds, for instance, offer good opportunities in track construction, which it says has been proved for both heavy loaded and high-speed tracks.
Namely, the use of asphalt provides positive contribution to the bearing capacity of the structure, as well as its stability and durability. The report says it can be divided between use as sub-ballast layers and use as full-depth construction – or ballast-less track.
Ryan Jansz, National Pavement Manager, from construction materials and building products supplier Boral, says asphalt has many technical advantages compared with traditional railway line construction that make it an ideal application to help cater for Australia’s increasingly diverse rail requirements.
“Asphalt reduces the load transmitted to the subgrade – and subgrade deformation is one of the structural controls used in rail track design,” Mr. Jansz explains.
“Using asphalt also reduces track irregularities and retains this uniform composition over time because it is a bound and engineered construction material.”
It additionally helps to reduce damage and ground vibration in rail tracks by a combined effect of reducing acceleration and deceleration of peak load values, as well as reducing tensions and fatigue on the sub-ballast.
Mr. Jansz adds that asphalt also reduces the magnitude of seasonal variations in vertical displacement of the rail head, thereby helping reduce damage or wear on rolling stock.
With this in mind and growing demand for alternatives to traditional railway line construction, Boral has developed an Australia-first product – Railpave.
The firm’s development brings what it calls the first engineered asphalt rail pavement construction product purpose-designed for rail track construction to the national market.
“Railpave opens up possibilities for more highly engineered, optimised ballast-less track design for the Australian rail sector, which should deliver efficiencies compared to the centuries-old ballast track with links to days of the steam engine,” Mr. Jansz explains.
“We designed it to meet the overall track design produced by a rail contractor and rail asphalt performance requirements, as based on overseas experience, and relating to Australian Standards and measurements.”
The product is designed for use in ballast-less or part-ballasted track construction on a commercial scale, including freight and passenger lines and even fast rail pavements.
It’s also designed for use in specialised loading and construction situations, including approaches to railway stations, suburban rail track transitions and sidings and turnouts where changes in ground or structural profiles occur or there is weak subgrade.
“The structural benefits include an increased structural capacity, less vibration – which can be augmented by incorporating either rubber or polymer to assist – reduced erosion, offset ballast fatigue and no fouling or contamination, which happens with ballast that is affected by environmental and rolling stock dust,” Mr. Jansz says.
“Railpave is also bringing that flexibility of application, the potential for fast construction turnaround and the ability to regulate and reduce maintenance at changes between track profiles,” Mr. Jansz adds.
Boral advocated for the use of Railpave as part of a project in Branxton, New South Wales. The product was successfully used as a rail track structural element for a heavy-axle-load coal mine track on the project, exemplifying its suitability for freight and other heavy haul mine lines across the country. It was also applied as a sub-ballast in Marulan, New South Wales, to showcase the efficacy of the asphalt in a different type of track profile.
Mr. Jansz explains that the product is designed with durability to cater to future growth of Australia’s rail industry, particularly with environmental impacts, sustainable outcomes and preserving natural resources front of mind.
“As with all other asphalt products, Railpave provides the benefit of longevity and its contribution to whole-of-life costs of any infrastructure project it is applied to,” Mr. Jansz says.
“We’ve tailored the product so that it aligns with the rail industry’s fast rail ambitions, carrying the world’s heaviest axle loads in the mining sector and national freight infrastructure, such as the Inland Rail project.”