Rammed earth is considered one of the oldest and, at the same time, most sustainable building materials in construction history. In everyday language, it is often referred to as the soil excavated during building projects. For construction purposes, however, this soil must meet specific requirements in terms of consistency, grain size, and composition. That’s why the clay is often processed and supplemented with targeted additives such as sand, gravel, or clay modifiers to optimize its building quality.
Despite this processing, rammed earth remains an almost limitless, natural material. Moreover, its use generates significantly less CO₂ emissions than comparable products like cement, making rammed earth an increasingly relevant, climate-friendly alternative in the construction industry.
Research at the gbd Testing, Technology, and Training Center
Since 2018, the gbd Testing, Technology, and Training Center has been dedicated to the systematic study of the material properties of rammed earth. The goal is to further develop this building material and expand its applications in modern construction.
In over 2,000 tests, key performance indicators have been analyzed, including:
- Compressive strength and its influencing factors
- Shear strength
- Creep and shrinkage
- Sound insulation
- Thermal conductivity
- Screw withdrawal resistance
Special attention is given to compressive strength, which is crucial for the load-bearing capacity of rammed earth walls. Factors such as optimal moisture content during construction, the slenderness of structural elements, shape factors, the ideal manufacturing method, and grain size distribution are studied in detail.
This research allows for precise adaptation of material properties to different applications—whether in load-bearing or non-load-bearing components—while simultaneously meeting the building physics requirements for sound and thermal insulation.
Clay-Wood Composites – Synergies Between Natural Building Materials
In addition to pure clay research, the gbd Center focuses on combining rammed earth with wood. Clay and wood complement each other perfectly in their material properties: while wood provides structural strength, clay regulates humidity and temperature and enhances acoustic insulation.
A practical example is ceiling elements developed by Lehm Ton Erde Baukunst GmbH, where wooden beams carry the load while rammed clay arches are placed in between. Extensive testing has been conducted on these composite elements, including impact and airborne sound measurements as well as vibration analyses. Both fully manufactured elements and conventional floor constructions were examined to validate the performance of the clay-wood system in real-world applications.
The results of this research help establish rammed earth as a modern, sustainable building material while simultaneously highlighting the innovative capabilities of the gbd Testing, Technology, and Training Center in ecological construction.
