The Elgip-Symposium on Innovative and Sustainable Materials for Geotechnical Applications was hosted at Technische Universität Darmstadt on 11th of March 2026.

The event brought together speakers, participants, and contributors for an engaging and insightful exchange. The symposium was characterized by scientific rigor, practical relevance, and honest discussions on the opportunities and challenges of sustainable innovation in geotechnics.

• Jürgen Rödelopened the symposium by emphasizing the urgency of sustainable action and the important role of science in this context. His thought-provoking question – whether we behave like humans, sheep, or frogs – set the tone for the day.

• Eddie Koenders presented the latest research on carbon-neutral concrete and alternative binders in concrete. Given the high consumption of cement and concrete also in geotechnical engineering, this is clearly a key topic for the future.

• Michael Harbottle took us into the world of programmable materials and nature-based solutions. It was fascinating to see, for example, how small amounts of energy can be stored underground using bacteria.

• Stefan Ritter shared results from a major research project on alternative binders for dry deep mixing, covering the full range from laboratory testing to field application. Particularly valuable was his honest view on implementation: some materials perform very well technically, but feasibility also depends on availability and scalability. A good example is paper sludge ash – promising as a binder, but produced in quantities too small to support broad practical use in ground improvement.

• Maren Katterbach and Dimitrios Terzis showed the commercial application of bio-cementation in geotechnical projects, while also addressing its current limitations in practice.

• Looking back on almost two decades of research and practice, Leon van Paassen gave impressive insights into bio-cemented soils, supported by both laboratory and field results. One key takeaway was that the method is especially suitable where moderate strength increases or limited cementation are needed. Its real sustainability potential lies not in copying conventional cement performance, but in replacing cement in cases where its properties would actually exceed what is required – for example in erosion control.

The symposium demonstrated that sustainable geotechnics extends beyond new materials and methods. It requires a comprehensive understanding of where innovations create genuine value, what obstacles need to be addressed, and how to implement advances responsibly in practice.

A special thank you to Tone Ratcliffe Smaavik and Jan Machaček for the great co-organization and moderation.

And many thanks to Julia-Isabelle Ruopp for the smooth and seamless organization throughout the event!