Cardboard and earth are being reimagined as building blocks for low-carbon construction, thanks to new research from engineers in Australia.
Researchers at RMIT University have developed cardboard-confined rammed earth — a material that uses only cardboard, water and soil.
With about one quarter of the carbon footprint of concrete and under one third of the cost, the material has the potential to cut emissions and divert millions of tonnes of waste cardboard from landfill.
In Australia alone, more than 2.2 million tonnes of cardboard and paper are discarded annually, while cement and concrete production contributes roughly 8 per cent of global carbon emissions.
The RMIT team was inspired by past innovations, including Shigeru Ban’s Cardboard Cathedral in Christchurch, New Zealand, but for the first time has merged the strength of traditional rammed earth with the versatility of cardboard.
Lead author Dr Jiaming Ma said the breakthrough represents a step forward in making sustainable construction mainstream.
“Modern rammed earth construction compacts soil with added cement for strength. Cement use is excessive given the natural thickness of rammed earth walls,” he said.
“But cardboard-confined rammed earth, developed at RMIT University, eliminates the need for cement and boasts one quarter of the carbon footprint at under one third of the cost, compared to concrete.
Ma said the use of just cardboard, soil and water can create walls sturdy enough to support low-rise structures.
He added that the approach has the potential to transform building practices by drawing on recyclable, locally available materials, while also aligning with the broader resurgence of earth-based construction driven by net zero ambitions and the push for sustainable resources.
The method involves compacting soil and water inside cardboard formwork on site, either by hand or with machinery.
Emeritus Professor Yi Min ‘Mike’ Xie, the study’s corresponding author, said the approach can simplify building while cutting costs and emissions.
“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,” Xie said.
“This would significantly cut transport costs, simplify logistics and reduce upfront material demands.”
According to Ma, the solution is particularly suited to construction in regional Australia.
“Rammed earth buildings are ideal in hot climates because their high thermal mass naturally regulates indoor temperatures and humidity, reducing the need for mechanical cooling and cutting carbon emissions,” he said.
The strength of the material depends on the thickness of its cardboard casing.
“We’ve created a way to figure out how the thickness of the cardboard affects the strength of the rammed earth, allowing us to measure strength based on cardboard thickness,” Ma said.
The research adds to a growing body of studies into alternative earth-based construction.
In a separate project led by Ma, carbon fibre was combined with rammed earth, demonstrating a strength comparable to high-performance concrete.
Ma and his team are now seeking industry partners to advance cardboard-confined rammed earth for commercial use.
The study, Cardboard-confined rammed earth towards sustainable construction, by Jiaming Ma, Hongru Zhang, Vahid Shobeiri, Ngoc San Ha, Srikanth Venkatesan, Dilan Robert and Yi Min ‘Mike’ Xie, is published in Structures.
Related research, CFRP-confined rammed earth towards high-performance earth construction, appears in Composite Structures.
