Researchers at RWTH Aachen University are investigating whether steel scrap can be transformed into certified, load-bearing construction components using 3D printing. The BMWE-funded AddMamBa project focuses on producing optimized facade brackets from recycled steel powder via laser powder bed fusion (PBF-LB/M), aiming to reduce material consumption and improve circularity in the construction sector.
The research is led by the university’s Chair Digital Additive Production (DAP) in collaboration with Paul Kamrath Ingenieurrückbau GmbH, RSB Rudolstädter Systembau GmbH, and Laser Melting Innovations GmbH. The project is funded by the German Federal Ministry for Economic Affairs and Energy under the Lightweight Technology Transfer Program and managed by Project Management Jülich.
From steel scrap to PBF-LB/M-qualified powder
AddMamBa examines whether recycled structural steel can meet the quality requirements for additive manufacturing of load-bearing facade connections.
Steel scrap is first sorted according to age, grade, and condition before being chemically analyzed. The material is then converted into metal powder using gas atomization (VIGA). Following atomization, the powder is sieved to a particle size range of 15–45 micrometers, suitable for stable layer deposition in the PBF-LB/M process.
Approximately 60% usable powder was recovered during the trials, yielding 30 kg of powder from 50 kg of processed scrap.The recovery rate, combined with chemical sorting and atomization control, indicates that recycled structural steel can be processed into powder with characteristics suitable for structural additive applications.
Topology optimization and thermal performance
The project focuses on facade brackets for ventilated facade systems and structural connectors for load-bearing uses. Topology optimization places material along the load paths, reducing unnecessary mass while keeping mechanical performance.
In addition to structural performance, the optimized shapes are designed to reduce thermal bridging. The brackets can be adapted to the building geometry and substructure setup without dedicated tooling, allowing customized production without extra mold costs.
A digital planning tool developed within the project assists users in selecting appropriate bracket solutions. After entering facade and structural data, the system proposes suitable configurations while considering relevant standards, including DIN EN 1991-1-4/NA.
Life cycle assessment and operational trade-offs
A Life Cycle Assessment (LCA) carried out under DIN EN 15804 reports a Global Warming Potential of 23.8 to 33.5 kg CO₂ equivalents per kilogram of component, based on projected 2030 electricity mix scenarios.
The analysis indicates that higher manufacturing-related emissions from the additive approach can be offset through operational energy savings, particularly in buildings using conventional gas heating systems. When paired with modern heat pump systems, the operational offset effect is reduced.
To improve circularity, the brackets are designed to be taken apart, with materials separated and reused. The consortium presents this as an important contribution to closing material loops in structural steel applications.
Why recycled feedstock is rarely AM-ready
Introducing new steel feedstocks into additive manufacturing is typically constrained by qualification and repeatability requirements. Metal powder supply chains for structural applications are built around tightly controlled chemistries and certified production routes. Producers must ensure consistent alloy composition, particle morphology, oxygen content, and flow behavior across batches. Even when base material properties appear comparable, certification pathways and downstream validation requirements make alternative feedstock sources difficult to introduce into structural applications.
Recycled materials introduce additional variability. Scrap steel can originate from multiple grades, service histories, and exposure conditions, creating challenges around traceability, contamination control, and chemical consistency.
Converting heterogeneous scrap into powder suitable for laser powder bed fusion requires careful sorting, compositional analysis, atomization control, and particle size classification before qualification testing can begin.
Against this backdrop, the AddMamBa project’s demonstration that sorted structural scrap can be processed into PBF-LB/M-ready powder for facade brackets represents a measured step toward integrating secondary steel into certified additive manufacturing workflows for construction.
Qualification of recycled steel for structural AM
Gas atomization and PBF-LB/M are established processes within metal additive manufacturing. What is less common is integrating recycled structural steel into that process chain while aligning with structural standards relevant to facade systems.
By combining scrap sorting, compositional analysis, controlled atomization, and topology-optimized design, AddMamBa integrates recycled steel into a workflow typically reserved for primary alloy supply chains.
For architectural firms, facade contractors, and connection element manufacturers, the research outlines a pathway for incorporating secondary materials into certified additive manufacturing workflows. The results may also be relevant to powder producers exploring alternatives to virgin alloy sourcing in structural applications.
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Featured image shows the workflow for the development of the topology-optimized facade bracket. Image via RWTH Aachen University.
