A new building material made from cardboard, soil, and water could slash the carbon footprint of traditional concrete by more than 75%, all the while cutting the construction cost to one-third of current pricing. That is, according to researchers at Melbourne-based RMIT University, who have developed a fully reusable and recyclable “cardboard-confined rammed earth” that they claim could be an ideal material for low-rise buildings at remote construction sites with red soils.
“By simply using cardboard, soil and water, we can make walls robust enough to support low-rise buildings,” according to Dr Jiaming Ma, lead author of the RMIT study, who added that eliminating cement from the mix slashes emissions tied to concrete—which accounts for about 8% of global CO₂—without compromising structural integrity.
The new material utilises compacted local soil and water within lightweight cardboard tubes that serve as both formwork and containers: “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,” said Emeritus Professor Yi Min “Mike” Xie, an expert in structural optimisation, who added that the tubes can be assembled by hand or with standard ram-press machinery, enabling rapid and low-cost construction in urban and remote settings.
New material could be a game-changer for outback construction
As it stands, Australia sends about 2.2 million tonnes of cardboard and paper waste to landfill each year; however, by repurposing discarded cardboard as structural formwork, the RMIT approach tackles both landfill overflow and construction emissions. Once a building reaches the end of its service life, the cardboard casing can be removed, recycled or reused in new projects—completing a closed-loop lifecycle.
Beyond the environmental gains, rammed earth walls also harness high thermal mass to stabilise indoor conditions: “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,” said Ma, who added that passive climate control also translates into lower energy bills and a smaller operational carbon footprint over a building’s lifespan.
To guide applications, the team developed mathematical models that link cardboard thickness to compressive strength. This framework allows engineers to tailor wall dimensions and formwork specifications to meet local load-bearing requirements with confidence. In a supporting study, Ma’s team showed that weaving carbon fibre strands into the earth mix transforms its performance. Even a small fibre fraction enhances both compressive and flexural strength to levels comparable to those of high-performance concrete—opening the door to mid-rise buildings and heavier load-bearing structures without compromising sustainability.
Now seeking commercial partners, researchers want to pilot full-scale projects and establish on-site tube manufacturing pathways. The findings appear in the journal Structures under the title “Cardboard-confined rammed earth towards sustainable construction,” co-authored by Jiaming Ma, Hongru Zhang, Vahid Shobeiri, Ngoc San Ha, Srikanth Venkatesan, Dilan Robert and Yi Min “Mike” Xie.
