By mixing cardboard, soil, and water researchers have made a strong construction material that has one quarter of cement’s carbon footprint.
The low-tech material is strong and stable enough to make walls for low-rise structures. And builders could make it with easily available locally sourced materials, according to the research published in the journal Structures.
“The construction industry is a major contributor to global carbon emissions, accounting for approximately 39 % of energy-related carbon dioxide emissions worldwide,” Yi Min Xie, a structures and materials researcher at RMIT University and colleagues write in the paper. About 11% of those emissions come from the production, transportation, installation, and disposal of building materials.
The cement industry alone is responsible for 8% of global carbon emissions. Researchers and companies are trying to reduce this carbon footprint by using low-carbon or natural building materials, and by recycling construction materials, among other things.
Xie and his team turned to cardboard, which can be a sustainable material and is produced in vast quantities. In Australia alone, more than 2.2 million tons of cardboard and paper are sent to landfill each year.
The researchers chose cardboard as the central material in rammed earth construction. Rammed earth is an old building method that involves compacting damp soil, sand, and clay layers into a wall. In modern rammed earth construction, buildings add cement to compacted soil for strength. And typically, too much cement is used given the natural thickness of rammed earth walls.
So the researchers came up with an innovative cardboard-confined rammed earth technique. They made 20 cm tall cardboard cylinders with walls ranging from 1-4 mm in thickness. Then they packed moistened locally sourced soil into the tubes using industrial hammer-like equipment.
The new cardboard-confined rammed earth eliminates the need for cement. Strength tests show that the rammed earth core “significantly enhances the structural performance of cardboard by more than tenfold, surpassing the strength of widely used cement-stabilized rammed earth,” the authors write.
In addition, the material would result in one quarter of the carbon footprint at under one third of the cost compared to cement, the researchers calculate. These reductions in carbon emissions and competitive life cycle costs make it “an appealing solution for sustainable low-rise building applications.”
Source: Jiaming Ma et al. Cardboard-confined rammed earth towards sustainable construction. Structures, 2025.
