RMIT Cardboard-Confined Rammed Earth (CCRE)

Product · Structural Systems

Product · InnDex 15 · Evidence provided · High specification risk

Cardboard-wrapped uncemented rammed earth columns eliminating Portland cement and embodied carbon.

CCRE addresses high-carbon concrete and cement in structural framing by confining raw rammed earth in thin cardboard tubes to create load-bearing columns. Lab testing at RMIT shows compressive strength exceeding cement-stabilised rammed earth with embodied carbon of 17.41 kgCO₂e/column. No full-scale prototype, field pilot, or long-term durability data exist.

RMIT's CCRE research confines uncemented rammed earth within thin cardboard tubes to produce structural columns that lab testing shows exceeding the compressive strength of cement-stabilised rammed earth — at an embodied carbon of 17.41 kgCO₂e per column. For designers seeking low-carbon structural systems without Portland cement, those headline numbers are notable enough to warrant attention, and one provided evidence point reflects the published lab result. The critical qualification is that everything beyond compressive strength in controlled lab conditions is unknown: cardboard durability under any real moisture exposure — rain, rising damp, high humidity — is the most serious concern, since softening or delamination of the confinement tube under sustained load could lead to sudden column failure with no prior deflection warning. There are no full-scale prototypes, no field pilots, no long-term durability data and no established regulatory pathway under any building code that currently recognises this structural typology. Uncemented rammed earth is also inherently more susceptible to water ingress than cement-stabilised material, compounding the moisture vulnerability. The building environments that tend to favour low-carbon structural systems — coastal, humid, temperate with freeze-thaw — are precisely those where cardboard confinement is least defensible. This research is worth following as full-scale testing begins; it should not move out of the research-tracking category until field performance data are published.

Strengths

• Dramatic embodied carbon reduction vs. cement-stabilised rammed earth and conventional concrete columns
• Maintains or exceeds compressive strength of stabilised alternatives in lab conditions
• Eliminates Portland cement, reducing operational and supply-chain carbon
• Uses abundant, recyclable cardboard as structural confinement material

Considerations

• Cardboard durability and moisture resistance unvalidated in field; risk of delamination, softening, or biological degradation in wet/humid exposure (critical)
• No reuse pathway demonstrated; cardboard confinement likely single-use, limiting circular economy claims (moderate)
• Uncemented rammed earth has higher sensitivity to water ingress and capillary wicking without cement binder protection (high)

Risks

• No full-scale prototype or field pilot data; compressive strength claims based on lab testing only; real-world load and settlement behaviour unknown (critical)
• Long-term durability and moisture performance in coastal, high-humidity, or freeze–thaw climates not evidenced (critical)
• Regulatory acceptance and building code compliance pathway unclear; may require extensive testing before adoption (high)
• Manufacturing quality control and consistency of cardboard confinement unclear at scale (moderate)
• Interaction between uncemented earth and cardboard under sustained load, thermal cycling, or shrinkage not characterised (moderate)

Performance

• Embodied carbon vs concrete: -77.7% (17.41 kgCO₂e per column, paper LCA)
• Embodied carbon vs cement-stabilised RE: -38.6%
• Cardboard tube thickness tested: 1–4 mm
• Deployment stage: Lab only — no full-scale or field build

Reality check

Lab cylinder compression tests documented in peer publication; LCA modelling completed at lab scale only. No evidence of: full-scale column fabrication, field deployment, durability trials (water ingress, cardboard degradation under load/moisture), long-term structural performance, constructability assessment, cost analysis, or reusability validation. Source is RMIT press release, not peer-reviewed journal. Cardboard tube specification (1–4 mm wall, type, wet/dry behaviour, fire rating) not detailed in available excerpt.

#rammed_earth #low_carbon #cardboard_confinement #embodied_carbon #cement_reduction

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