New building material is strong, cheap, and sustainable

ByDr. Tim Sandle
SCIENCE EDITOR

DIGITAL JOURNAL
October 23, 2025


Construction site (London, UK). Image by Tim Sandle.

Engineers in Australia (RMIT University) have developed a new building material with about one-quarter of concrete’s carbon footprint, while reducing the level of waste going to landfill.

The development is a cement-free construction material made by using only cardboard, soil, and water (hence the name for the aterial, which is ‘cardboard-confined rammed earth’). The material is strong enough for low-rise buildings and it can be formed on-site, making it ideal for remote areas. In addition, the thermal properties naturally cool buildings.

Overall, the rammed earth core significantly enhances the structural performance of cardboard by more than tenfold.

Process

The cardboard-confined rammed earth can be made on the construction site by compacting the soil and water mixture inside the cardboard formwork, either manually or with machines. With the soil, earth is pre-processed through desiccation and sieving to regulate moisture content and grain size distribution for sample preparation. The cardboard tubes serve as permanent formwork, confining the rammed earth core.

The mechanical strength of the novel material varies based on the thickness of the cardboard tubes. To enhance the process, an AI an analytical model was developed to predict the compressive strength of the material cylinders with varying dimensions.

For the study, four cardboard tube thicknesses—1 mm, 2 mm, 3 mm, and 4 mm—were used to examine how varying tube thickness impacts the mechanical performance of the CCRE cylinders. The tubes had a consistent height of 200 mm and an inner diameter of 100 mm across all samples, with each thickness category having three specimens for a series of repetitive tests.

The compression tests are conducted using a hydraulic testing machine with a constant loading rate of 500 Newtons. A Newton is a measure of pressure, where a Newton equates to the force that accelerates a mass of one kilogram at one metre per second squared. The measurement of global strain was obtained by dividing the recorded displacement of the loading platen by the initial specimen height.

In a second study, carbon fibre was combined with rammed earth, proving it had a comparable strength to high-performance concrete.

Application

Rammed earth buildings are ideal in hot climates because their high thermal mass naturally regulates indoor temperatures and humidity, reducing the need for mechanical cooling and cutting carbon emissions.

Sustainable

The researchers hope the material will provide a step toward greener, more resilient architecture. Cardboard-confined rammed earth eliminates the need for cement and it can be produced at under one third of the cost, compared to concrete.

The material is described in the journal Composite Structures, with the paper titled “CFRP-confined rammed earth towards high-performance earth construction.”