CASE STUDY
Greener Concrete Reinforcement for Improved Concrete Sleeper Applications by Associate Professor Olivia Mirza Nowadays, Australia’s population is over 25 million having increased by almost five times over the last century. As such, huge planning and investment are being made in the infrastructure to further overcome congestion and capacity issues. Accordingly, the railway connectivity will be an important factor towards the integration of regional and metropolitan economies for their mutual benefit. By 2075, the population is forecast to double putting huge constraints on the railway network which will be required to keep pace with such growing demand. For instance, by 2026 there is already a forecast growth of 19% and 26% in the passenger and freight operations respectively [1]. Therefore, increasingly railway operational conditions characterise faster average speeds and frequency of services requiring the Australian railway infrastructure to be properly maintained towards ensuring
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Waste + Water Management Australia | June/July 2020
the safety, reliability and efficiency in connecting regions and cities. One solution to this challenging task was to assess essential track components to ensure they could satisfy the line upgrades. According to researchers [2, 3], one of the critical track components is the sleeper which main function is to maintain the track gauge and redistribute the axle loads to the ballast. Typically, railway sleepers are made from timber, steel and prestressed concrete despite recent concerns associated to the degradation, durability and high-cost of such conventional materials. For instance, wooden sleepers offer a comparatively cheap, lightweight and easy to install option despite being far more prone to wear and tear particularly with the shortage of highquality timber. On the other hand, steel sleepers were often seen as a middle ground between
the wooden and concrete alternatives, offering better load-bearing capacities with reduced dependence on the ballast bed. However, steel sleeper implementation remained fairly limited due to major drawbacks such as susceptibility to corrode and fatigue cracking at the rail seat. In comparison, the modern prestressed concrete sleeper embodies superior load capacity, track stability and a longer service life requiring on average less maintenance. Other concerns related to the sleeper’s material have long been acknowledged, resulting in premature failure of conventional sleepers and their associated replacement cost incurred as shown in Figure 2. In other words, prestressed concrete sleeper is being the preferred option nowadays despite timber historically dominating as a railway sleeper material.
