In the summer semester of 2025, a pioneering research and development project in the field of 3D concrete printing (3D Concrete Printing, 3DCP) was launched at the Institute for Structural Design and Building Construction (KGBauko) at TU Darmstadt. Conducted in close cooperation with Sika Germany, the Riedel Bau Group, and Staikos 3D, the project exemplifies the growing integration of digital design, additive manufacturing, and sustainable building culture.

The goal of the project is the development and realization of a topology-optimized concrete slab with a span of 5 × 5 meters, designed as a free-spanning slab supported by a single mushroom-shaped central column. This slab is intended not only as a technical demonstrator but also as a basis for studying innovative construction methods and material-efficient structural systems. A key feature is the fully 3D-printed concrete formwork, which enables the slab’s complex geometry and ensures precise realization of the topology-optimized structure.

The construction industry is currently undergoing a profound transformation. Issues such as resource efficiency, sustainability, digitalization, and automation are gaining increasing importance. In this context, 3D concrete printing is considered one of the most promising technologies for reducing material consumption, shortening construction times, and increasing design freedom.

One of the greatest challenges for implementing additive manufacturing in construction practice, however, is the lack of standardized norms, testing procedures, and legal frameworks. To address these challenges, the project follows an innovative hybrid approach. The 3D-printed formwork is used as an integral formwork system, reinforced with conventional steel reinforcement, and subsequently filled with cast-in-place concrete. The result is a load-bearing structural component that meets building regulations while also being technologically advanced.

The printed formwork serves multiple functions at once. First, it precisely reproduces the complex rib geometry of the slab and visually reveals the internal flow of forces. Second, additive manufacturing enables the creation of geometrically demanding shapes that would be neither economically nor technically feasible with traditional formwork methods.

By strategically placing material only where forces actually occur, the structure achieves high load-bearing capacity with minimal material use and the lowest possible self-weight—an essential principle of topology-optimized construction. In doing so, the project makes an important contribution to conserving resources and reducing the CO₂ footprint in the construction sector.

This close integration of digital design, manufacturing technology, and practical construction highlights the potential of an integral planning process in which design, structural engineering, and production are deeply interconnected.

The full-scale 1:1 demonstrator was produced at the Riedel Bau Talentfabrik in Schweinfurt. After intensive planning and testing, the reinforcement work was successfully completed. The 3D-printed formwork elements were assembled with precise fit, and the system was then monolithically cast with in-situ concrete.

During the planning phase, load tests and material analyses were conducted to evaluate the component’s load-bearing capacity, deformation behavior, and durability. The insights gained will contribute to future research projects as well as potential standardization processes for additive construction methods.

The accompanying illustrations and drawings document each step of the project—from the 3D printing of the formwork to the integration of reinforcement, concreting, and completion. They provide a fascinating insight into the emergence of a new generation of concrete structures that combine design freedom, technical precision, and ecological responsibility. The project exemplifies KGBauko’s commitment to linking research, teaching, and practice in construction and shaping the building culture of tomorrow.

Institute KGBauko, TU Darmstadt:
Prof. Dipl.-Ing. Architect Stefan Schäfer, Nikola Bisevac
SIKA Germany: Dr.-Ing. Slava Markin, Dr.-Ing. Shifan Zhang
Riedel Bau Group: Dr.-Ing. Rebecca Wolff, Thomas Bauer, Christian Seuling, Timo Helemann
Staikos 3D: Georgios Staikos, Yannik Berkensträter
Participating students: Alessandro Garruto, Ahmet-Münir Telci, Max Rösner, Summer Wazy