3D concrete printing – numerical and experimental description of the sub- processes extrusion, material deposition and layer-by-layer build-up

• Applicants: Professor Dr.-Ing. Viktor Mechtcherine; Professor Dr. Günther Meschke
• Subject Area: Applied Mechanics, Statics and Dynamics ; Construction Material Sciences, Chemistry, Building Physics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 545131259

3D printing with concrete has a high potential to substantially increase productivity and sustainability in the construction industry and to counteract the increasing shortage of skilled labor. The research project focuses on the experimental and numerical investigation of the flow and deformation processes of concrete during the sub-processes of 3D concrete printing, namely, extrusion, material deposition, and layer-by-layer build-up. The results from the project should, on the one hand, enable a significantly more precise and reliable design of the production processes in comparison to the current state-of-the-art, and, on the other hand, allow a better prediction of the quality of additively manufactured concrete structures. The research work focuses on the development of a numerical model to describe the printed concrete structures during and after material deposition. This requires the experimental investigation and model-based characterization of elasto-viscoplastic deformations in the fresh state as well as plastic deformations due to hydration, shrinkage and creep in the hardening state, including hygrothermal interactions. For this purpose, experimental methods for the characterization of fresh concrete during and after the printing process are explored and complemented by photogrammetric methods for non-contact deformation analysis. Novelty of the developed multi-level simulation strategy is associated with the seamless description of the concrete in the fresh and hardening state in a single numerical model and the consistent connection of simulations on the filament and the scale of complete structures encompassing the material extrusion, deposition, and layer-by-layer build-up. The numerical model is calibrated with data from the experimental studies and is systematically validated by means of various experimental benchmark studies at the filament and component scale. At the filament scale during material extrusion and deposition, comparative studies are carried out for analyzing deformations and filament geometries and their changes after deposition. At the scale of structural components, stress states, forces, and deformations during layer-by-layer build-up are comparatively examined. As an application example, the penetration and enclosure of reinforcing grids is investigated in detail experimentally and numerically when they are covered with concrete by means of 3D printing. Thus, the project also contributes to the integration of reinforcement into 3D concrete printing technologies.

• DFG Programme: Research Grants