Researchers at the Royal Melbourne Institute of Technology (RMIT) in Australia have unveiled a groundbreaking building material that combines rammed earth with permanent cardboard formwork. This innovative approach eliminates the need for cement, traditionally used to strengthen rammed earth structures, thereby reducing the material’s carbon footprint.
Typically, rammed earth walls are constructed by compacting layers of soil mixed with 8 to 10 percent cement within temporary moulds. These moulds are removed once the earth stabilizes, leaving behind durable, dense walls. However, the RMIT team has discovered that by encasing the compacted earth in lightweight cardboard tubes, they can create a low-carbon, lightweight, and thermally insulating composite suitable for low-rise and modular buildings.
Revolutionizing Construction Materials
The findings of this research were recently published in the journal Structures, and the team estimates that this new material, known as CCRE (cardboard-confined rammed earth), could be ready for commercial testing within one to two years. The researchers believe that by combining rammed earth with cardboard, they can significantly reduce embodied carbon while providing a recycling pathway for waste cardboard.
In a world where buildings and construction materials such as concrete and steel contribute to 37 percent of annual CO2 emissions, with the cement industry alone responsible for 8 percent, there is a pressing need for sustainable alternatives. This development follows a growing trend among architects and engineers to explore low-carbon materials like mass timber, adobe, and rammed earth.
Environmental Challenges and Opportunities
The use of cardboard as a packaging material has surged alongside the e-commerce boom, leading to significant waste management challenges. In 2020 and 2021, cardboard and paper accounted for 7.7 percent of all waste generated in Australia, with 2.2 million tons ending up in landfills.
“This creates both an environmental challenge and an opportunity,” said Dr. Jiaming Liu, one of the study’s lead researchers. “Repurposing cardboard for construction not only diverts it from landfill but also transforms it into a valuable, ultra-low-carbon building resource.”
In conventional rammed earth construction, soil is compacted inside temporary formworks—usually made of plywood or steel—that shape the wall. Once the earth hardens, these formworks are removed. With CCRE, the cardboard acts as permanent formwork, providing continuous confinement to the rammed earth core.
Innovative Design Inspired by Shigeru Ban
The RMIT team drew inspiration from Japanese architect Shigeru Ban, renowned for his use of structural cardboard in temporary shelters and various structures. Ban’s Cardboard Cathedral in Christchurch, New Zealand, completed in 2013, sparked the idea of combining cardboard’s structural properties with rammed earth.
To date, the team has constructed small-scale CCRE prototypes to evaluate the material’s mechanical strength, carbon footprint, and lifecycle performance. Liu noted that the prototypes demonstrated CCRE’s compressive strength is comparable to cement-stabilized rammed earth, with roughly one-quarter of concrete’s embodied carbon.
Additionally, the team has developed a related version using carbon-fiber confinement, achieving strength levels comparable to high-performance concrete. Looking ahead, the researchers plan to construct full-scale CCRE columns and experiment with formworks that extend beyond simple cylindrical shapes.
Future Prospects and Potential Impact
The team envisions foldable, origami-inspired cardboard moulds that could be transported flat and quickly assembled on-site. This innovation could pave the way for custom, modular, and easily deployable construction systems.
The implications of this research are significant, offering a sustainable alternative to traditional construction materials and providing a new use for waste cardboard. As the world grapples with climate change and the need for sustainable development, innovations like CCRE could play a crucial role in reducing the environmental impact of the construction industry.
With commercial testing anticipated in the near future, the RMIT researchers’ work represents a promising step towards more sustainable building practices. The photography accompanying this article is courtesy of RMIT.
