
Researchers at the Royal Melbourne Institute of Technology (RMIT) in Australia have unveiled an innovative building material that could revolutionize sustainable construction. By encasing rammed earth in permanent cardboard formwork, they have eliminated the need for cement, creating a low-carbon alternative suitable for low-rise and modular buildings.
Traditionally, rammed earth walls are constructed by compacting layers of soil mixed with about 8 to 10 percent cement within temporary molds. These molds are removed once the earth stabilizes, resulting in a dense, durable wall. However, the RMIT team proposes a novel approach by confining the compacted earth within lightweight cardboard tubes, thereby removing the need for cement altogether.
Recycling Cardboard for Construction
The research, published in the journal Structures, suggests that this new material, dubbed cardboard-confined rammed earth (CCRE), could be ready for commercial testing within one to two years. The innovation not only reduces embodied carbon but also offers a recycling pathway for waste cardboard, addressing two significant environmental challenges simultaneously.
Buildings and construction materials, such as concrete and steel, account for 37 percent of the world’s annual CO2 emissions, with the cement industry alone responsible for 8 percent. This has prompted architects and engineers to seek low-carbon alternatives like mass timber, adobe, or rammed earth. The use of cardboard as a packaging material has also surged with the e-commerce boom, leading to increased waste management challenges. In 2020 and 2021, cardboard and paper made up 7.7 percent of all waste generated in Australia, with 2.2 million tons sent to landfill.
“This creates both an environmental challenge and an opportunity,” Dr. Jiaming Liu, one of the study’s lead researchers, told Dezeen. “Repurposing cardboard for construction not only diverts it from landfill but also transforms it into a valuable, ultra-low-carbon building resource.”
Structural Innovation and Inspiration
In conventional rammed earth construction, soil is compacted inside temporary formworks, usually made of plywood or steel, which are removed after the earth hardens. With CCRE, the cardboard serves as permanent formwork, performing the same shaping role during construction while providing continuous confinement to the rammed earth core.
“It not only performs the same shaping role during construction but also provides continuous confinement to the rammed earth core,” said Liu. The synergy between the two materials is evident: the cardboard enhances the rammed earth’s strength and resistance to cracking or seismic forces, while the earth reinforces the cardboard’s compressive performance by more than tenfold.
The team drew inspiration from Japanese architect Shigeru Ban, known for his pioneering use of structural cardboard in temporary shelters and other structures. Ban’s Cardboard Cathedral in Christchurch, New Zealand, completed in 2013, sparked the idea of combining cardboard’s structural properties with rammed earth.
Prototypes and Future Prospects
So far, the team has built small-scale CCRE prototypes to evaluate the material’s mechanical strength, carbon footprint, and life-cycle performance. Liu reported that these prototypes demonstrated compressive strength comparable to cement-stabilized rammed earth, with roughly one-quarter of concrete’s embodied carbon.
The researchers have also developed a related version using carbon-fiber confinement, achieving strength levels comparable to high-performance concrete. Moving forward, they plan to construct full-scale CCRE columns and experiment with formworks that extend beyond simple cylindrical shapes.
The team envisions foldable, origami-inspired cardboard molds that could be transported flat and quickly assembled on-site, paving the way for custom, modular, and easily deployable construction systems.
The photography is courtesy of RMIT.