Bridges

Ultra-High-Performance Concrete (UHPC) has been in use internationally since around the year 2000, with numerous bridges constructed using this advanced material – including a notable example in New South Wales. UHPC is characterized by its exceptionally high mechanical performance, with a minimum compressive strength of 150 MPa and tensile strengths (both pre- and post-cracking) exceeding 5 MPa. Its dense matrix, combined with the inclusion of short, discontinuous steel fibers, significantly reduces capillary porosity, enhancing durability and resistance to environmental degradation.

To support the broader adoption of UHPC in Australia, a local material specification is currently under development to address the sensitivity and variability of its constituents. Additionally, the AS 5100 code committee is working on design guidance to provide engineers, contractors, and asset owners with the confidence needed to specify UHPC in infrastructure projects. The adoption of UHPC offers several advantages over conventional concrete, including superior compressive and tensile strength (relative to conventional concrete), minimal shrinkage and creep, enhanced resistance to carbonation, chloride ingress, and water penetration – all contributing to an extended service life and reduced maintenance demands.

In the context of rail bridges carrying 245LA rail loading, the current standard solution for simply supported spans up to 36 metres is the use of multiple Super T girders with an in-situ concrete deck. For spans exceeding 36 metres, steel trough girders made composite with concrete decking are commonly used in both simply supported and continuous span arrangements. However, this steel-based solution is significantly more expensive and has a much higher embodied carbon footprint compared to concrete alternatives. Replacing steel trough girders with UHPC Super T girders for spans up to 50 metres presents a compelling opportunity. This approach not only lowers construction construction costs and carbon emissions but also aligns with sustainable infrastructure goals, without compromising on performance or durability.