Engineers at RMIT University in Australia have introduced an innovative building material that boasts a carbon footprint roughly one-quarter that of traditional concrete. This new material, named “cardboard-confined rammed earth,” combines cardboard, soil, and water, thereby significantly reducing landfill waste.
The strength of this composite material makes it suitable for constructing low-rise buildings, and its capacity for on-site formation renders it particularly advantageous for remote locations. Additionally, the thermal characteristics of this material aid in naturally cooling structures.
By significantly enhancing the structural performance of cardboard, the rammed earth core improves its strength more than tenfold. The production process involves compacting a soil and water mixture within cardboard formwork, which can be accomplished either manually or through machinery. To prepare the soil, it is desiccated and sieved to achieve the desired moisture level and grain size.
The cardboard tubes serve as permanent formwork, enclosing the rammed earth core. The mechanical strength of this material varies depending on the thickness of the cardboard tubes used. An analytical model powered by artificial intelligence was developed to predict the compressive strength of cylinders made from this material, taking into account different dimensions.
The research utilized four thicknesses of cardboard tubes—1 mm, 2 mm, 3 mm, and 4 mm—to assess how varying thicknesses affect the mechanical performance of the cardboard-confined rammed earth cylinders. Each tube measured 200 mm in height and had a consistent inner diameter of 100 mm, with three specimens in each thickness category subjected to repeated testing.
Compression tests were performed using a hydraulic testing machine, applying a constant load of 500 Newtons. A Newton is defined as the force needed to accelerate a one-kilogram mass by one meter per second squared. The global strain measurement was calculated by taking the recorded displacement of the loading platen and dividing it by the initial height of the specimen.
In a separate study, researchers combined carbon fiber with rammed earth, achieving strength levels comparable to high-performance concrete. Structures built with rammed earth are particularly effective in hot climates, as their elevated thermal mass helps regulate indoor temperatures and humidity, thereby minimizing reliance on mechanical cooling and reducing carbon emissions.
The researchers envision that this groundbreaking material could pave the way for more sustainable and resilient architectural practices. By eliminating the need for cement, cardboard-confined rammed earth can be produced at less than one-third of the cost of concrete.
This innovative material is detailed in the journal Composite Structures, in a paper titled “CFRP-confined rammed earth towards high-performance earth construction.”
