Concrete is polarising. For many, there is endless beauty in its solidity and purity, while for others, its reductive qualities are offensive. Add its reliability as a building material and its problematic environmental impact to the mix and, simply put, the topic of concrete is divisive. As the most resilient, robust and cost-effective material known to us, it’s favoured by architects, designers and builders around the world – even by those for whom sustainability is paramount. So does concrete have a place in the realm of responsible design and construction, or does its sizeable contribution to atmospheric carbon dioxide outweigh its benefits?
Modernism, and brutalism in particular, put concrete on the map as a material with not only structural but aesthetic value. The work of iconic 20th century architects such as Paulo Mendes da Rocha and Le Corbusier, with their extraordinary use of the material, is highly persuasive in recognising concrete’s virtuosity. Closer to home, significant late-modern brutalist buildings such as the National Gallery of Australia and the High Court in Canberra are widely regarded for their sensitive use of concrete. Most renowned of all, the engineering feat that is the Sydney Opera House was made possible thanks to the epic proportions of its precast concrete shells. As contemporary architecture continues to explore the potential of concrete, today, it is the most widely-used construction material in the world. Alarmingly, due to the limestone heated to make cement – a key component of concrete – it’s responsible for around eight per cent of global annual carbon emissions, and this fact has the industry seeking out alternatives and striving for more efficient solutions.
“‘Ethics over aesthetics’ is a mantra often repeated in our studio and is a filter of scrutiny for all materials we specify,” explains Bonnie Herring, Director of Architecture and Head of Sustainability at Breathe. “The use of concrete is a decision made on balance between the environmental impact of its sourcing and manufacture, and the ongoing benefit to the comfort and quality of the building.” This sentiment seems to be widely understood. The damaging environmental effects linked to the production of concrete can’t be denied, but its benefits around thermal productivity and durability also hold weight. Scott Burchell, Founder of COMB Construction, says “in the past, we’ve been lazy about the way we use concrete – pouring mass concrete footings and using it in excess. We need to be smarter, and it’s slowly changing.” Scott believes in harnessing concrete’s permanence and taking advantage of its unrivalled longevity to “futureproof” the built environment, designing and building structures that will endure for generations to come.
Andrew Maynard, Principal at Austin Maynard Architects, agrees, saying “we need to consider the longevity of a building – that’s the real sustainability argument.” He believes architects and designers must be conscientious in their use of concrete. “It’s all about getting the fundamentals right,” he says, adding, “if you’re going to use concrete, you’ve got a responsibility to think about the buildability of that material.” The practice’s recently completed multi-residential project in Brunswick, Terrace House, demonstrates this idea through the concrete boundary walls, where the architects “went to great lengths to create a thermal break.” What’s more, the ground floor slab utilises 50 per cent recycled and reclaimed aggregate and 50 per cent fly ash in the concrete. As a result, the concrete makes a positive contribution to this building’s status as passive and sustainable, and true to the architects’ wishes, it’ll stand as part of this community for a few hundred years thanks to its structural integrity.
Alongside adopting more intelligent methods, the industry can specify greener products, too, with some of Australia’s largest concrete producers including Boral, Holcim and Hanson introducing low carbon concrete. Nermine Zahran, Senior Associate and Sustainability Manager at Koichi Takada Architects, says the practice hasn’t ruled out concrete altogether, instead it carefully considers embodied carbon and smarter alternatives. “We acknowledge that concrete is still the dominant material for construction and, therefore, we specify low-carbon concrete that reduces the carbon intensity by 30-60 per cent.”
As cement is the root of the problem, reducing the cement content is the most explored technique in improving the material’s environmental impact, with fly ash, wood ash, silica fume and granulated slag stepping in as partial replacements. Bonnie says that Breathe is using “an increased quantum of recycled content in the mix,” such as recycled water and organic and recycled aggregate. Carbon sequestration in concrete is also gaining legs, as companies around the world look to produce concrete that captures more carbon than it omits. The challenge here, Andrew explains, is that these products often come at a financial cost, and some feature a longer cure time due to the reduced cement content. Yet factoring these considerations into a project’s budget and timeline could have a profound effect on the industry’s hefty CO2 emissions.
Ignorance surrounding unsustainable materials simply doesn’t fly in 2022. The industry is coming to recognise it has a responsibility to challenge traditional methods of design and construction, and to explore, prototype and specify environmentally conscious concrete options. Encouragingly, an awareness of concrete’s chequered reputation and an informed approach to its consumption are on the rise as we navigate its challenges and opportunities.