Researchers at RMIT University have developed a groundbreaking building material called cardboard-confined rammed earth made from cardboard, soil and water that not only reduces carbon emissions and cost but also minimises waste destined for landfill.

Australia alone sends more than 2.2 million tonnes of cardboard and paper to landfill each year, while cement and concrete production contributes roughly 8% of annual global emissions. The RMIT team’s cardboard-confined rammed earth eliminates cement entirely, achieving just one quarter of the carbon footprint of concrete at less than one third of the cost. The new material is both reusable and recyclable, making it an important development for sustainable construction.

Cardboard has previously been used to build temporary structures and disaster shelters, inspiring the RMIT team to combine the durability of rammed earth with the versatility of cardboard, while removing cement from the process.

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“Modern rammed earth construction compacts soil with added cement for strength. Cement use is excessive given the natural thickness of rammed earth walls,” explains lead author Dr Jiaming Ma.

“By simply using cardboard, soil and water, we can make walls robust enough to support low-rise buildings,” Ma says. “This innovation could revolutionise building design and construction, using locally sourced materials that are easier to recycle.”

“It also reflects the global revival of earth-based construction fuelled by net zero goals and interest in local sustainable materials.”

The material can be produced directly onsite by compacting the soil and water mixture inside the cardboard formwork, either manually or with machines.

Observing that the innovation can spearhead a leaner, greener approach to construction, study corresponding author and leading expert in the field of structural optimisation, Emeritus Professor Yi Min ‘Mike’ Xie says, “Instead of hauling in tonnes of bricks, steel and concrete, builders would only need to bring lightweight cardboard, as nearly all material can be obtained on site. This would significantly cut transport costs, simplify logistics and reduce upfront material demands.”

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Cardboard-confined rammed earth is particularly suited to remote areas such as regional Australia, where red soils ideal for rammed earth construction are abundant. Ma adds that rammed earth buildings are ideal for hot climates because their high thermal mass naturally regulates indoor temperatures and humidity, reducing the need for mechanical cooling and cutting carbon emissions.

The mechanical strength of the material can be adjusted according to the thickness of the cardboard tubes, the researchers say.

Ma has also led another study where carbon fibre-reinforced polymer (CFRP) was combined with rammed earth, proving it had a comparable strength to high-performance concrete.

The researchers are now seeking industry partners to scale and commercialise their cardboard-confined rammed earth innovation for broader use.

‘Cardboard-confined rammed earth towards sustainable construction’, with RMIT co-authors Jiaming Ma, Hongru Zhang, Vahid Shobeiri, Ngoc San Ha, Srikanth Venkatesan, Dilan Robert and Yi Min ‘Mike’ Xie, is published in Structures. (DOI: 10.1016/j.istruc.2025.110117)

Main image: Cardboard-confined rammed earth column and CFRP-confined rammed earth column

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