Research summary report of A10

Earth Additive Manufacturing (EAM) – Material and Process Combinations for AM with Earth-based Materials

[13.05.2026]

Machner, Alisa; Project Leader, alisa.machner@tum.de

Tsiotou, Sofia; Doctoral Researcher, sofia.tsiotou@tum.de

Technical University of Munich, TUM School of Engineering and Design, Professorship for Mineral Construction Materials

Project A10 aims to design and investigate two novel processes for Earth Additive Manufacturing (EAM), namely, Sprayed Earth Additive Manufacturing (SEAM) as a deposition-based EAM process, and Intrusion Earth Additive Manufacturing (IEAM) as a particle-bed-
based EAM process. Alongside the investigations on the two processes, earthen binder mixtures will be evaluated from a material’s perspective regarding the material-process interaction and their variability and suitability for large scale EAM applications. The assessment of both methods and materials will revolve around tackling issues commonly associated with Earthen Construction such as shrinkage, long drying times and strength development and additionally issues introduced with Additive Manufacturing such as maintaining pumpability while ensuring sufficient buildability during the construction of 3D-printed elements.

Summary

The sub-project summarized in this report highlights the significance of the origin of earthen raw materials used in earthen binders for EAM, as reflected in the quality and quantity of clay minerals as well as the presence of non-clay mineral phases. As earthen construction is re-emerging and gaining popularity in the industry, significant research and development efforts are underway to standardize
earthen raw materials for specific applications. The composition and origin of materials from different geographical locations in Germany and worldwide need to be further investigated in order to generate data that can eventually be used to predict the suitability of different soils for EAM.

The present study investigates the microstructure of a range of different earthen materials and focuses on identifying properties that can help assess the suitability of these materials for 3D printing. We distinguish between two main deposits of clay minerals, primary and secondary, with primary being a product of chemical weathering of silicate feldspathic host rocks in high energy environments [1] and secondary being formed from the physical weathering of minerals as they undergo transportation, erosion and sedimentation further away from the host rock setting [2].

In earthen construction raw materials are mostly sourced from secondary clay deposits, which causes clay minerals to exhibit a higher disorder degree (Figure 1) and to also include phases created through diagenesis (alteration of sediments during burial) such as illite (2:1) (K₀.₇₅Al₂(Si₄O₁₀)(OH)₂·nH₂O).

Weathered earthen materials also tend to have higher amounts of non-clay minerals such as feldspars and carbonates as well as iron oxides and hydroxides. The overall effect of weathering results in a higher Specific Surface Area (SSA) and a shift in the grain size distribution both of which are expected to affect the rheological behavior and strength gain during drying of earthen materials.

Current state of research
During the first part of the study in 2024 – 2025 we managed to establish a promising fundamental characterization protocol for a set of different clay products with variable clay mineral contents and qualities, which allows tracking the effects of mineralogical (clay minerals and bulk chemistry) and physicochemical properties (grain size and surface charges) directly to the rheological and mechanical properties of earthen binders.

The relationship between material mineralogy (microstructure), workability (fresh-state) and mechanical (hard-state) properties is currently being evaluated through analysis of X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR) and rheology and strength investigations, with the aim of determining the origin of the available SSA in each clay material and how it reflects on the particle-water interaction and therefore on the performance of the material as an earthen binder. Solid state NMR is currently being implemented in an attempt to more closely characterize the microstructure of clay minerals and H1 NMR (relaxometry) is tested for observing the saturation and drying mechanism, meaning the rate with which the water is entering and leaving the mineral structure, more closely.

Material rheology is currently tested by means of penetration measurements and flow table slump tests. The goal is to observe the material behavior for the first few hours after mixing and to correlate the results to mineral microstructural data. To further investigate the microstructure in the hardened state CT scanning is currently implemented for visual observations.