The research project "MaBo – Material Savings in bored piles" demonstrates in an exemplary and practice-oriented manner how the use of 3D-printed recess formers (hollow bodies) in bored piles can save substantial amounts of concrete, thereby reducing resource consumption and CO2 emissions in geotechnics. The innovation lies in targeted optimization of the pile cross-section and the substitution of low-utilized regions without impairing the load transfer behaviour via end bearing and shaft friction. This addresses a previously underexplored application field that directly aims at sustainable building, remains compliant with existing codes, and bridges research and construction practice.

To develop the solution, conventional bored piles were first modelled and analysed using finite element methods to derive robust criteria for identifying cross-section segments suitable for optimization. On this basis, practice-ready hollow-body geometries were created whose positioning, dimensions, and transition zones were chosen so that they do not negatively affect the actions governing loadbearing capacity. The designs were iteratively verified numerically and then manufactured as prototypes using concrete 3D printing, with particular attention to material properties, manufacturing tolerances, and integration in reinforcement cages. Laboratory verification included compression and tension tests to establish resistance parameters, as well as investigations into friction between 3D-printed surfaces and fresh concrete, to reliably quantify buoyancy safety during concreting. These findings supplement classical Archimedean considerations by showing that frictional forces at the contact surfaces make a significant counter-contribution to buoyancy and must therefore be considered methodologically. Finally, the optimized bored pile was produced in the field. The entire process chain—from design and manufacturing to installing the hollow bodies in the reinforcement cage, concreting, and near-component testing—was documented, proving practical feasibility under real boundary conditions.

The results show that hollow bodies can be positioned and dimensioned so that structural safety and stiffness are preserved while material demand is significantly reduced. Manufacturability was demonstrated under practice-relevant conditions, including the specific requirements of transport robustness, positional stability in fresh concrete, and concreting with restricted insertion of the concreting pipe. The tightness and bond of the 3D-printed components in the pile cross-section were confirmed in the field. For transfer to application, the findings on design, fabrication, and verification were structured and accompanied by an initiated design approach based on numerical calculations and component tests. This approach forms the starting point for an analytical design concept and a construction guideline enabling designers to apply the technology in practice with-out exclusive reliance on FEM software.

For users, technical and economic advantages arise: more efficient construction procedures with unchanged loadbearing capacity and serviceability, a measurably improved sustainability profile, and a competitive edge by positioning as a pioneer in sustainable building. Looking ahead, consistent implementation can unlock considerable savings, with annual potentials on the order of several thousand tonnes of CO2 and clear reductions in material consumption. The consortium-based cooperation between research and industry, field-near demonstration, and planned exploitation activities—from publications and guidelines to training—ensure reach and impact of the project results in science and practice and facilitate transfer into teaching and execution.

The outlook focuses on standardization and scaling of the method. Required steps include an expanded data basis, additional laboratory and field tests to calibrate interaction effects, normative embedding of verifications, and the development of a consistent construction and design guideline with execution rules, tolerances, and test criteria. With these steps, the technology can be routinely incorporated into planning practice, increase application safety, and broadly scale the sustainability contribution in geotechnics.

Project management

Graz University of Technology - Institute of Structural Design

Project or cooperation partners

• Carinthia University of Applied Sciences
• Keller Grundbau Ges.mbH

Technische Universität Graz – Institut für Tragwerksentwurf
Univ.Prof. Dr.-Ing. Stefan Peters
Technikerstraße 4/4
A-8010 Graz
Tel.: +43 (316) 873 6211
E-mail: stefan.peters@tugraz.at
Web: ITE - Home (tugraz.at)