Soil-ed
Sewage derived bio-stabilisers for earth construction
A.A.Z. Goldsmith Ganzerli (TU Delft - Architecture and the Built Environment)
Olga Ioannou – Mentor (TU Delft - Architecture and the Built Environment)
M. Overend – Mentor (TU Delft - Architecture and the Built Environment)
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Abstract
This research investigates the potential of wastewater-derived extracellular polymeric substances (EPS), commercially recovered as Kaumera, as a bio-based stabiliser for earth construction. The study addresses a gap in existing literature concerning the use of secondary biopolymers recovered from wastewater treatment as alternatives to conventional cementitious stabilisers.
A research-through-making methodology was adopted. Compressed earth block specimens incorporating EPS in both dry powder and gel form were produced and evaluated through compressive strength testing, water resistance testing, and qualitative assessment of aesthetic and sensory characteristics. Multiple experimental series were undertaken to investigate the influence of binder format, concentration, curing procedures, and soil composition.
The results demonstrate a consistent positive relationship between EPS content and water resistance. Gel-based formulations were particularly effective, with specimens remaining intact after prolonged submersion and significantly outperforming unstabilised controls. Increased EPS content also improved surface quality, reduced drying cracks, and enhanced edge definition. In contrast, compressive strength results were highly variable. While certain gel formulations achieved strength increases of 30-48% relative to baseline samples, subsequent test series produced contradictory outcomes. Dry EPS formulations consistently reduced compressive strength and were therefore considered unsuitable under the tested conditions.
The findings suggest that EPS has considerable potential as a durability-enhancing stabiliser for earthen materials. Proposed applications include erosion protection elements, exterior earth plasters, and earth-based acoustic barriers. Although further investigation is required to understand the underlying stabilisation mechanisms and long-term performance, the research establishes a promising foundation for the use of wastewater-derived biopolymers in circular construction systems.