Precast concrete, produced by casting concrete in a reusable mould, is a method of construction that has existed for a long time, dating back to ancient Roman buildings.
Manufactured in controlled factory environments, precast concrete is usually transported to site and lifted to place during construction.
According to the National Precast Concrete Association of Australia, precast concrete provides significant benefits in terms of quality, construction, strength, safety and even sustainability. The product goes up quickly, is long lasting (structures can last for hundreds and even thousands of years) and fire safe, and has energy saving benefits from high thermal mass.
Precast concrete is furthermore a highly versatile product, as the use of moulds coupled with specialised manufacturing and high tech materials have allowed architects to design and specify different shapes and forms of precast concrete, often with varying colours, patterns and textures. The way the material is produced also makes sharp detailing and, if desired, more intricate finishes possible.
Modern precast concrete remains a common material in many building and architecture industries around the world, Australia notwithstanding. Here, we look at five modern Australian buildings that have made the most out of this age-old construction method.
Stamp House by Charles Wright Architects
Designed for clients who wanted an estate that withstands intense weather while enhancing its natural wetland environment, Stamp House is essentially a cyclone proof structure that sits over an engineered water eco-system. Its massive cantilevers mitigate the impact of potential flooding and king tide inundation associated with cyclone activity in the area.
The structure, a combination of precast and in-situ concrete, is ideal for its location due to its inherent long life cycle efficiency and material properties, which allows it to deal with the harsh, corrosive wet tropical environment. The concrete was engineered and insulated, and incorporates a total solar panelled roof.
Image: Patrick Bingham Hall. Source: Charles Wright Architects
Described by the architects an “enigmatic bunker”, the concrete is also expected to age over time and feature a ‘patina’, which will further enhance the house’s sense of place in the environment.
Oracle by DBI Design
Image: Frazer East
Oracle is a luxury mixed-use development in Broadbeach, Queensland consisting of two apartment towers set 180 degrees from each other. Over 1,540 exterior precast panels, featuring both convex and concave curves, were used to create the unique ‘S’ shape design of the project.
Interestingly, many of the panels have subtly different shapes for each floor, so that just over 500 different panel forms were utilised for the project. To meet the program schedule, Precast Concrete Products had to cast 10 panels a day.
Image: Matthew Hofmann. Source: world-architects
Apart from the curved façade, precast panels were also used for the edge of the structural formwork. They contain cast-in starter bars which were used to attach the panels, and create the structural balcony elements and perimeter of the building.
Edithvale Wetlands Discovery Centre by Minifie van Schaik (MVS) Architects
Image: Peter Bennetts. Source: archello
Completed in 2012 for Melbourne Water, the centre perches over the Edithvale wetlands, a place for visitors to explore and understand the history and workings of the urban wetland and its role in the water-cycle.
The building features a glass reinforced concrete (GRC) shell, which was supplied and erected by Asurco Contracting. Weighing only 10 per cent of conventional precast, a lighter custom timber moulding was used to create the elaborate and detailed valley-and-ridge pattern.
"Using GRC meant we could make moulds from laminated MDF boards direct from the architect’s 3D drawings using a 5-axis CNC router,” Aurco’s managing director Des Pawelski explained.
“We coated the custom wood with epoxy and a skin of tooling resin which worked very well for limited-use moulds. As well as giving us a precision finish, we also had to use four different moulds. If the panels were cast as conventional precast panels, then the moulds would have been far more costly.”
Source: Fabulously Fabricated
Altogether, 40 wall panels of various sizes were used for the project. The concrete was also impregnated with a charcoal pigment that takes on different hues depending on the play of light.
Hawke Building by John Wardle Architects and Hassell
The Hawke Building at the University of South Australia is named after former Prime Minister Bob Hawke, and defined as the gateway to the civic expression of the campus. Its façade is made up of misaligned precast concrete panels, each one different to the next. This complexity presented challenges for SA Precast, which needed to not only ensure the 68 panels were consistent in colour, but also that the geometry of their features remained accurate and in line with the architects’ intent.
Image source: John Wardle Architects
Modelled first in 3D by a specialist façade engineer, the panels were cast face down on complex moulds of concrete, steel and timber. The off-white finish was achieved using 45 MPa concrete comprising Salisbury aggregate, white sand and Brighton Lite Cement.
Coated with an anti-graffiti and anti-pollution treatment, inserted copper accents have allowed the façade to weather gracefully.
Melbourne Recital Centre by ARM
GRC is once again the highlight of another building, this time the Melbourne Recital Centre in Victoria. The architects were tasked to design a building that, as the pinnacle for musical appreciation and performance, would feature both excellent acoustic quality and amenity. Employing cost-effective and environmentally sustainable methods were also important for the clients.
Meeting the requirements presented in the brief, GRC was used in conjunction with glass, and bluestone brickwork for the façade. The pattern of the concrete had to be defined, with all individual pieces interlinked. Steel framework was fixed into the rear of each panel for structural strength, while acting as a connection medium for fixing the panels to the building structure.
Image source: ARM
The ‘bubble’ effect of the GRC panels, likened to the polystyrene insulation used in gift packaging, was created using specialised moulds. According to the National Precast Association, these were created by stapling a polyurethane moulding onto melamine-coated particleboard, which was in turn placed inside each steel mould. When the mould was removed, the moulding stripped away cleanly to reveal the pattern.
