Precast concrete components used in buildings or infrastructure are typically manufactured offsite in reusable moulds, resulting in precise and durable precast elements that greatly enhance a project’s sustainability and have limitless design possibilities.
Precast concrete manufacturing uses less raw material compared to in-situ concrete pours, which along with the use of recycled materials substantially reduces the volume of construction waste generated by a project.
Selection of building materials and choice of construction method are key ways of improving sustainability, according to the National Precast Concrete Association Australia, making precast concrete the obvious choice due to its inherent properties.
National Precast noted that manufacturers were always looking for opportunities to reuse, reduce and recycle, with grey and storm water runoff utilised, waste materials from other industries incorporated, the minimal production waste recycled, and moulds often reused hundreds of times.
The fast and cost-efficient construction process also leads to safer sites and minimal disturbance, while the precast elements themselves are long-lasting, maintenance-free, termite-proof, flood and fire safe, requires no chemical treatment, and does not emit any fumes.
National Precast said: “Longer lasting structures are more sustainable as they can be reused, extended or refitted internally rather than simply being demolished – precast is perfect for long life structures, being tough and durable and having a long life expectancy.
“Precast concrete actually gains strength as it ages – it won’t shrink, distort or move and will not deteriorate with exposure to climatic change.”
Importantly, the high thermal mass of precast concrete allows the material to absorb, store and radiate heat, enabling natural heating and cooling processes via passive solar energy.
This allows buildings constructed using precast components to substantially reduce energy costs as well as the associated carbon emissions and environmental impacts.
A study from 2022 which systematically analysed the construction methodology and sustainability performance of 38 construction projects in Hong Kong across two decades found significant positive correlations between the percentage of precast concrete applied onsite and a project’s sustainability attributes.
Further analysis suggested that the highest sustainability performance was found in projects that primarily used a modular integrated construction methodology.
The researchers added: “The analysis from a wide range of construction projects over a long period of time suggests that the findings are generally applicable, and not limited by the projects’ location, project size, project type, and project duration.”
A PRACTICAL AND SUSTAINABLE DESIGN AESTHETIC
Precast concrete is being extensively used in Perth’s first major elevated rail project, which entails the removal of six level crossings along the Armadale line by raising the rail over the road at the existing intersections.
Due for completion in 2025, the METRONET Victoria Park-Canning level crossing removal project will reduce traffic congestion and improve safety with nearly four kilometres of overhead rail, as well as creating a new public space.
Funded by both state and federal government, the project is using 260 prestressed L beams for the main viaduct, with the design of the 31-metre-long, 130-tonne beams a first for Western Australia.
Forty prestressed 29.9-metre T beams will become station platforms, while 480 reinforced headstocks and supporting column segments are being manufactured for below the viaduct – these components weigh between six and 120 tonnes.
Precast concrete was selected for the project due to its recognised durability and efficient onsite installation that met the tight construction schedule, with the main challenge in controlling the temperature of concrete elements as they cure.
This is being managed through extensive thermal modelling and the design and application of thermal controls, including internal and external cooling of the elements and their moulds, monitoring concrete supply temperatures, concrete mix trials, and dispensation from specific limits.
Another ongoing WA project utilising precast components is the 64-kilometre Bindoon Bypass along the Great Northern Highway, which is a vital transport link to the state’s northern region.
The $275-million project will improve freight productivity and safety and includes new bridge and causeway structures that cross the Brockman River and its tributaries.
A key requirement of the works is to minimise impacts on existing waterflow paths and regimes, as well as to maintain water quality in the waterways and wetlands within or adjacent to the development envelope.
National Precast Chief Executive Officer Sarah Bachmann explained that highly durable and long-lasting precast box culverts offered an ideal solution, with the causeway structures designed to span minor watercourse crossings and wetlands while maintaining water flows and minimising flooding.
Bachmann added: “The culvert causeways would be integral to ensuring proper water drainage while maintaining the integrity and functionality of the road.
“[This is] particularly important in WA, where variable weather conditions – including heavy rainfall and occasional flooding – can impact the stability of the road and compromise the safety of travellers.”
To enhance the sustainability of the development, innovative stormwater management systems were incorporated, recycled materials were used and erosion control measures were implemented.
A notable example of the versatility provided by precast elements is the complex diamond-embossed precast concrete façade panels used on the redesigned Coburg Station in Melbourne, which was completed in 2021.
Bachmann added that precast concrete was highly suited to precise, architectural-grade applications such as Coburg Station, as it was perfect.
