Concrete is the world’s second most used material after water. Its binder, cement, produces about 8% of global carbon emissions and accounts for 90% of concrete’s footprint. Reducing this impact is key to meeting the Paris Agreement’s 2030 and 2050 targets, especially in the Netherlands where low-emission housing solutions are urgently needed. Previous work on CoRncrete, a cornstarch-based concrete, demonstrated the potential of cement-free binders but was limited by poor water resistance.

This research builds on that foundation through a four-phase Material Driven Design approach. Context and material research included bench-marking, interviews, and desk study. In the tinkering phase, recipe adjustments, sealers, and surface treatments were explored, with preliminary submersion tests leading to a revised process of wet pressing and post-curing (minimizing manufacture steps), and the addition of eggshell powder as partial sand replacement. Technical characterization then tested mixes with 7.5%, 10%, and 12.5% sand replacement with eggshell powder under varied curing times, climates (5 °C/60% RH, 30 °C/60% RH, 30 °C/80% RH), and submersion conditions, using triplicate samples. Results showed a improvement in water resistance: all recipes withstood at least 24 hours of immersion compared to 10 minutes for the original mix, while the 12.5% eggshell variant achieved the highest compressive strength (14 MPa after 21 days). Experiential characterization with nine participants found a preference for eggshell-based samples, with plain, marbled, and pigmented finishes each valued for different architectural applications, as assessed with the MDD toolkit.

The final material, named Agristone, is produced as a pre-cast block (300 × 100 × 200 mm), aligning with standard concrete block dimensions for straightforward adoption in low-rise inner-leaf or partition walls. With a compressive strength of 14 MPa, Agristone falls within the range of structural lightweight concrete (11.8–21 MPa) (Ansys Granta Edupack), ensuring its technical viability. It is available in a palette of natural oxide colors, reducing finishing needs and adding design flexibility. Life cycle comparisons indicate ~45% lower CO₂ eq emissions and 60% lower embodied energy than conventional lightweight concrete. Costs of Agristone are estimated to be higher than concrete blocks (€1.55/block vs. €0.89/block), but these may be offset by the material’s sustainability, reduced construction steps, and aesthetic added value.

This work demonstrates that a cornstarch-based concrete with eggshell additive and simplified manufacture method can achieve both structural performance and moisture resistance, establishing Agristone as a promising step toward bio-based, cement-free construction materials.