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New sustainable building material from cardboard, soil and water
Engineers at RMIT University in Australia have developed a cement-free construction material made only from cardboard, soil and water. Called cardboard-confined rammed earth, the material delivers roughly one quarter of the carbon footprint of conventional concrete while also diverting cardboard waste from landfill. According to the researchers, it is strong enough to form load-bearing walls for low-rise buildings and offers thermal benefits that reduce cooling needs in hot climates.
Why this matters for low-carbon construction
Cement and concrete production contribute about 8% of global CO2 emissions; at the same time, Australia sends more than 2.2 million tonnes of cardboard and paper to landfill annually. The RMIT team combined the long-established concept of rammed earth—compacted soil walls—with lightweight cardboard formwork to create a reusable, recyclable structural element that avoids cement altogether.
Lead author Dr Jiaming Ma explains the innovation's practical advantage: "Modern rammed earth construction compacts soil with added cement for strength. Cement use is excessive given the natural thickness of rammed earth walls." The RMIT design removes the cement requirement and, the team reports, achieves comparable structural performance for many low-rise applications at under one third of concrete's cost.
How it is made and its practical benefits
Cardboard-confined rammed earth is produced on site by placing a soil-and-water mix inside cardboard tubes or formwork and then compacting it manually or with machinery. The cardboard confines the compacted soil during curing and can be reused or recycled afterward. Emeritus Professor Yi Min "Mike" Xie, corresponding author and structural optimisation expert, notes: "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. This would significantly cut transport costs, simplify logistics and reduce upfront material demands."
Thermal mass and climate resilience
Rammed earth structures have high thermal mass—meaning they absorb and slowly release heat—so walls made with this method naturally moderate indoor temperatures and humidity. In hot climates, that reduces reliance on air-conditioning and associated emissions, making the approach attractive for remote or regional areas where suitable red soils are common.
Structural performance and design considerations
The mechanical strength of cardboard-confined rammed earth depends on cardboard form thickness and compaction quality. The RMIT team developed a design formula that links cardboard tube thickness to expected compressive strength, enabling engineers to specify forms for particular load conditions. In related work, Ma combined carbon fibre reinforcement with rammed earth and demonstrated performance comparable to high-performance concrete in some tests—suggesting pathways to extend applications beyond low-rise construction.
Manufacturing on site reduces embodied energy from transport and the lightweight nature of the supplied materials simplifies logistics, particularly in remote communities or post-disaster reconstruction scenarios. The material also supports circular economy goals by diverting cardboard from landfill and using locally sourced soils.
Expert Insight
Dr. Hannah Reyes, a materials scientist specializing in sustainable construction, comments: "This approach revives centuries-old earth-building techniques with a modern, pragmatic twist. By quantifying how cardboard formwork affects structural performance, RMIT bridges laboratory research and on-site practicality. For regions with limited supply chains, the carbon and cost savings could be significant—provided builders adopt standard testing and quality control."
Future prospects and industry uptake
The research team is open to industry partnerships to pilot the material in real projects and refine production methods. Widespread adoption will require building-code validation, durability testing over seasons and treatments or design adaptations to address moisture in exposed locations. If those steps succeed, cardboard-confined rammed earth could be incorporated into sustainable housing, community infrastructure and modular construction systems.
Conclusion
Cardboard-confined rammed earth is a low-cost, low-carbon alternative to conventional concrete for many low-rise applications. By using cardboard, soil and water, the technique reduces emissions, diverts waste from landfill, cuts transport needs and offers thermal benefits that improve occupant comfort. With design formulas linking formwork thickness to strength and preliminary reinforcement studies indicating higher-performance options, this innovation represents a practical step toward greener, more resilient architecture.
Source: sciencedaily
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