Kaumera as a bio-based stabiliser for earth-based construction

Can Kaumera help make earth based construction materials stronger and more resistant to water? A TU Delft master’s thesis explored the use of Kaumera as a bio-based stabiliser for earth construction with promising results.

Earth is one of the oldest construction materials in the world and is attracting renewed interest because of its low embodied impact, local availability and potential for reuse. One of its main limitations, however, is its sensitivity to water. To meet modern performance requirements, earth materials are therefore often stabilised with cement or lime. These additions improve durability, but also increase the environmental impact of the material and can limit its recyclability.

This research investigated whether Kaumera, could provide an alternative stabilisation route. Kaumera (in both gel and dry powder form) was incorporated into compressed earth samples and tested for compressive strength, water resistance and other material properties. 

Gel Kaumera shows the most promising performance

One of the clearest findings was the difference between Kaumera gel and dry Kaumera powder. Under the conditions tested, products made with standard Kaumera gel performed better than those made with dry powder.

The gel formulations showed particularly strong results in water resistance testing. Increasing the amount of Kaumera generally improved durability, and several samples remained intact after prolonged exposure to water. In one test series, gel based samples showed almost no mass loss during immersion, while the untreated samples disintegrated within the same testing period. 

This effect was consistent throughout the research. The thesis concludes that improved water resistance is the clearest and most reproducible benefit of adding Kaumera to earth based materials. 

Researching the strength

The research also investigated whether Kaumera stabilised earth could achieve the mechanical performance required for construction.

The mechanical results were less consistent than the water resistance results. Later experiments showed that strength is strongly influenced by factors such as soil composition, Kaumera concentration, water content, curing and manufacturing conditions. Further testing is therefore needed before the effect of Kaumera on compressive strength can be fully understood. 

Appearance and behaviour 

The addition of Kaumera gel also influenced the appearance and behaviour of the earth material. Higher gel concentrations generally resulted in better cohesion, smoother surfaces, more defined edges and fewer drying cracks. 

These characteristics could make Kaumera particularly interesting for applications where resistance to weathering and surface quality are important. The research identifies potential directions including compressed earth products, exterior earth plasters, erosion control elements and infrastructure applications. 

A new direction for circular construction and biobased building

The project demonstrates a new potential use for Kaumera within the built environment. By combining an earth-based construction material with a functional biopolymer recovered from wastewater, the research connects two important developments in circular construction: the use of secondary raw materials and the transition towards bio-based alternatives to conventional binders.

The results provide a strong basis for further development. The next step is to produce additional samples and investigate how formulation, processing and curing can be optimised to achieve consistent performance. Further research is also needed into long-term durability, recyclability and environmental performance. 

While the technology is still at a research stage, the combination of strong water resistance, promising mechanical performance and circular material use makes Kaumera stabilised earth an interesting direction for future construction applications.