Brisbane-based global engineering and project management consultancy, Hatch, has found that using more green concrete could soon spearhead Australia’s action on climate change, if conservative construction industry attitudes shift.
The country would hit its climate targets much faster if the construction industry started using more of the green alternative which a Hatch report says is cheaper in the long term and comes with other benefits.
The report, by Hatch structural engineer Dr Ezgi Kaya, found that green concrete would save about 17 million tonnes of Australia’s annual 500 million tonnes of carbon emissions if we substituted it for half the traditional concrete we use.
“That’s equal to removing four million cars from our roads,” said Dr Kaya, whose calculations include the production of concrete — where most CO2 emissions occur — as well as installation costs including transport and use of other equipment.
The construction industry puts out 40% of world greenhouse gas emissions and 8% is from concrete production and installation.
Hatch specialises in big mining and minerals, infrastructure, and energy projects which use huge amounts of concrete and the consultancy was keen to investigate ways it could make its work more sustainable.
Dr Kaya’s report shows that, while versions of green concrete may be 5-20% more expensive to buy, the cost premium almost vanishes to 0.5 to 1.4% when the total installed cost is considered. Further, Dr Kaya and Hatch Consultant Process Engineer Scott Farquhar say the green alternative has many long-term benefits other than sustainability.
“Unlike conventional concrete which requires … considerable energy and resources to produce, green concrete often uses recycled materials and avoids or minimises use of Portland cement, a major contributor to carbon emissions,” says Dr Kaya.
Portland cement is the standard binder of ingredients for concrete and turning it into cement incurs significant greenhouse gas emissions. It’s hard to decarbonise concrete production because cement is produced in kilns where limestone is heated and carbon dioxide is released during calcination — so CO2 cannot be avoided by switching to using a different fuel.
One solution is partial replacement of cement content with naturally occurring materials such as volcanic ash and waste materials such as fly ash and slag. The other approach is to make a geopolymer concrete which uses different chemistry to avoid limestone and its emission of CO2.
Dr Kaya says Australia has high potential for using green concrete, because of an abundance of recycled aggregates, fly ash and slag which can be used instead of traditional aggregates and cement — thus making the production of green concrete here more environmentally friendly.
In Australia, all the major concrete suppliers provide low-carbon concretes. Hanson, Boral, and Holcim each offer a form of low-carbon concrete with reduced amounts of Portland cement which is supplemented with other ingredients. Wagners and Zeobond manufacture geopolymer concrete without any cement, achieving higher CO2 reduction of up to 80%.
As well as smaller carbon footprint for concrete production, additional benefits noted in the report are:
– Greater durability, less maintenance: green concrete has a longer life because it is shrink- and crack-resistant
– More fire resistant: green concrete often needs fewer coatings required by some conventional concretes to improve durability and fire resistance
– Better insulating properties: less energy is needed for heating and cooling a building made with green concrete
– Less waste: it uses recycled materials that could otherwise go to landfill
These qualities make green concrete especially suitable for demanding conditions, environments and the kinds of infrastructure projects on which Hatch works.
“Governments could … mandate use of green concrete in curbs and pavements.”
There are no real obstacles to a rapid rise in use of green concrete, according to Farquhar and Dr Kaya.
“Green concrete products cover a range of possibilities, depending on project needs and ingredients that need to be swapped in and out,” says Farquhar.
“The slow uptake is a cultural thing — people are reticent to be the first or early users of something new,” he says.
Dr Kaya believes the first priority is to incorporate new standards for green concrete into the general concrete standard AS3600.”
“I’m aware that Standards Australia intends to extend the current concrete standard to adopt green concrete options. And I’m hoping this is just a matter of time and we’ll soon have standards incorporating green concrete options soon including geopolymer concrete.
““To me this is just the beginning if we want to stay on this planetTo me this is just the beginning if we want to stay on this planet.”Secondly, she says governments could play a strong role to mandate use of green concrete in kerbs and pavements and other areas where governments use traditional concrete.
“Engineers are being conservative although the tech has been around for about two decades.”
“To me this is just the beginning if we want to stay on this planet.”
Initially, green concrete was more expensive but the price has been going down and will fall even further.
Airports from Toowoomba to Amsterdam to Dubai have used it, as have high-profile buildings such as the Louvre Abu Dhabi. The City of Gold Coast has built an artificial reef of geopolymer concrete as a diving attraction and the supplier, Wagners, reports that its use saved close to 100 tonnes of embodied carbon, equivalent to CO2 absorption by 95 acres of forest in a year. .
“As Australia pushes towards a sustainable future, adoption of green concrete is a crucial step in achieving decarbonisation goals. By embracing this innovative and environmentally friendly construction material, Australia can not only reduce its carbon footprint but also create a more sustainable and resilient built environment,” Dr Kaya says.
“To me this is just the beginning if we want to stay on this planet,” says Dr Kaya.
“I would like to see concrete not only become carbon neutral but carbon negative, because it could store carbon dioxide drawn down from the atmosphere.”
Although she says the technology is not quite ready, Canada is one country already experimenting with capturing and storing carbon in concrete.
Dr Kaya’s report is available on request to Hatch Australia.