Building using soil isn’t new. Structures dating back 10,000 years to Mesopotamia and the Near East were created using techniques like adobe (sun-dried bricks) and rammed earth, including the Great Wall of China.
But for most modern-day uses, it’s undesirable. It is vulnerable to water damage, has high maintenance needs, and exhibits low structural strength, as well as high shrinkage/swelling rates that cause cracks with changing weather.
But engineers in Australia have combined it with cardboard and water and produced a new material that has the potential to revolutionise the construction of low-rise buildings across the world.
Inspired by such designs, the RMIT University team has, for the first time, combined the durability of rammed earth with the versatility of cardboard.
Called cardboard-confined rammed earth, it’s ideal for hot climates like Australia’s due to its natural temperature regulation, and it suits remote construction anywhere red soils are available.
“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, eliminates the need for cement.
“By simply using cardboard, soil and water, we can make walls robust enough to support low-rise buildings,” Ma said.
“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.”
Cardboard-confined rammed earth has a carbon footprint that’s about 75 percent lower than concrete and costs about a third as much to produce, while being reusable and recyclable, thus reducing the waste going to landfill.
In Australia alone, more than 2.2 million tonnes of cardboard and paper are sent to landfill each year. Meanwhile, cement and concrete production account for about 8 percent of annual global emissions.
The cardboard-confined rammed earth can be made on the construction site by compacting the soil and water mixture inside the cardboard formwork, either manually or with machines.
The ability to produce it on-site significantly reduces transport costs and logistics—no more truckloads of bricks or relays of cement mixers travelling from centralised building material suppliers to remote Australian towns.
The strength of the material can also be adjusted simply by varying the thickness of the cardboard tube.
Another author of the study, who’s a leading expert in the field of structural optimisation, Yi Min “Mike” Xie, said this advancement can spearhead a leaner, greener approach to construction.
“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.”
Ma said cardboard-confined rammed earth could be an effective solution for construction in remote areas, such as regional Australia, where red soils—ideal for rammed earth construction—are plentiful.
“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 mechanical strength of the new material varies based on the thickness of the cardboard tubes, and Ma said the team has developed a formula so they can tell how thick they need to be for a particular application.
“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.
He and the team say they are ready to partner with various industries to further develop this new material so it can be widely used.
