Lower-emissions concrete mixes are getting bogged down in the wet cement of industry standards, preventing their wider use in construction.

A leading researcher has warned that industry codes and regulations, including the National Construction Code, are preventing lower-carbon concrete from being considered for major building projects.

The traditional manufacturing processes for Portland cement are highly polluting, contributing around 7 per cent of the world’s total carbon emissions each year. 

The Cement Industry Federation (CIF) claims the total emissions from cement in Australia during 2019-20 was 4.94 megatons, a 20 per cent reduction since 2010-11.

On Monday, a Materials and Embodied Carbon Leaders’ Alliance discussed the ways Australia’s concrete industry can reduce its carbon footprint in a webinar.

In his presentation, Professor Stephen Foster at the Faculty of Engineering at the University of New South Wales, highlighted some of the key innovations that can help reduce the overall carbon footprint of concrete structures.

The first is through the use of stronger concrete. This can be done by including a greater amount of cement in the concrete, or by including materials such as geopolymer plastics or high-strength reinforcing steel.

Professor Foster said efficiency gains from using these stronger mixes can mean less concrete needs to be used overall on a project. “By using twice as much cement per cubic metre, we use a third the amount of the total concrete. So we’re actually driving carbon down,” e told the webinar audience. 

Concrete manufacturers can also reduce their emissions by substituting high-carbon materials in their cement mixes with alternatives that give equal (or better) performance. These can include fly ash (a bi-product from burning coal) or blast furnace slag (from steelmaking).

The potential of these new forms of concrete has been demonstrated in a number of projects. These include Toowoomba’s Wellcamp Airport, Pinkenba Wharf in Brisbane, and a City of Sydney pavement trial.

Regulatory hurdles for cleaner concrete

Unfortunately, according to Professor Foster, industry design standards and building codes “can be a real roadblock” to their use in other construction projects.

“It can take 10 to 15 years to get [a new concrete technology] from research into enough demonstrations in industry to develop enough confidence that you can then put it into a standard and then implement it. [With the looming climate crisis], we don’t have 15 years in this space,” he said.

“Durability takes time for us to examine. We can’t wait 30 years for a new product or new material to be implemented because we don’t have all of the answers.”

Both industry standards and National Construction Code need to be more responsive to change.

“We need to speed up the pace of standardisation markedly. And if our aspiration is to get to net zero by 2050, we need to make sure we’ve got all of us – industry, researchers, and governments – defining those pathways.”

Scientific tests by universities, in partnership with industry and governments, can be used to speed up the pace that industry codes are updated.  

“What we can do is put scientific processes in place to provide the confidence that we need. We have a huge wealth of experience in concrete.”

“With new alternative binding concretes, whether they are a partial cement or a full cement replacement, we have to look to the science. If it’s carbonation that we’re interested in, [we need to] put processes in place, put the tests in place, put the performance criteria in place, so we can be confident with that aspect of the design.”

“The more trials we have, the more confidence we can have in the products. We’ve been arguing about this for too long. We have the technologies. It’s really time to start rolling them out.”

A seven-step plan for emissions reductions

In a separate presentation at the MECLA event, Cement Industry Foundation chief executive Margie Thomson highlighted the cement industry’s strategy for reducing its carbon emissions.

The strategy covers the full lifecycle of concrete buildings, from cement manufacturing through to the long-term use of buildings.

The plan was originally released in late 2021 in a report titled Decarbonisation Pathways for the Australian Cement and Concrete Sector, and was developed by the German cement industry research organisation VDZ.

According to the VDZ study, 55 per cent of emissions from the Australian cement and concrete sector come from calcination, which is the process of converting limestone into clinker and carbon dioxide. A further 26 per cent come from the fuel used to heat cement kilns, 12 per cent are from electrical energy use, and 7 per cent are from transport.

The report identifies eight main “pathways” that are needed for the sector to reach net zero emissions by 2050:

  • zero emission electricity and transport
  • innovation through design and construction
  • continuing to further innovate concrete
  • use of supplementary cement-like materials in concrete
  • new carbon-efficient cements
  • use alternative fuels and green hydrogen
  • account for concrete’s ability to absorb carbon dioxide
  • capture remaining carbon dioxide

However, Ms Thomson acknowledged that the full decarbonisation of the Australian concrete sector depends on the development of carbon capture and storage (or reuse) technologies. 

“When we’re looking at what technologies are available now, or likely to be available during the time period, we need to rely on CCS or CCU to fully decarbonise. However, there are many new technologies that are starting to come into play that could change that,” she said.

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