Old cardboard as a building material can save CO₂

Scientists at Australia's Royal Melbourne Institute of Technology (RMIT) have combined old cardboard, water, and soil to create a building material that has similar properties to concrete. This is essentially an ancient building technique using rammed earth, which is now coated with cardboard to give it greater strength. The material is said to be particularly suitable for low-rise buildings.

In their studies “Cardboard-confined rammed earth towards sustainable construction” and “CFRP-confined rammed earth towards high-performance earth construction,” which were published in Structures and Composite Structures, the researchers call the building material “cardboard-confined rammed earth,” which is also intended to be particularly sustainable. With their approach, the scientists want to kill two birds with one stone: eliminate the masses of cardboard waste and reduce the CO₂ emissions caused by cement and concrete production. Around 8 percent of CO₂ emissions worldwide are caused by cement and concrete production. In Australia alone, more than 2.2 million tonnes of cardboard and paper are produced every year, which are disposed of in landfills there, according to the researchers.

Using rammed earth and cardboard to combat CO₂ emissions

The construction technique designed by the scientists uses rammed earth, in which moist soil, sand, and layers of clay are compacted to achieve a certain degree of strength. As the base material is naturally occurring, it is sustainable. The use of cement is then not necessary.

Buildings made of rammed earth are ideal for hot climates. Their high thermal mass naturally regulates the indoor temperatures and humidity in the rooms. As a result, less energy-intensive cooling is required. This saves further CO₂ emissions, the scientists explain.

To increase the strength, the rammed earth is encased in cardboard tubes. The researchers can calculate exactly how thick the cardboard sheathing needs to be to achieve the desired strength. The scientists have also investigated how the strength of the material can be increased even further. They combined rammed earth and carbon fibre. Although the strength is then almost as high as that of high-performance concrete, this comes at the expense of the carbon footprint due to the carbon fibre used.

The production of “Cardboard-Confined Rammed Earth” is simple and can be produced directly on site. Soil and water are compacted manually or mechanically in a cardboard casing. On-site production eliminates the need to transport heavy building materials such as prefabricated concrete, steel, or bricks. This reduces transport expenses.

(olb)