circular construction

The Striatus, a first-of-its-kind 3D-printed concrete bridge, was presented during the 2021 Venice Architecture Biennale. The Phoenix Bridge, announced in January 2024, represents the evolution of the Striatus. 

Constructed at Holcim’s Innovation Hub in Lyon, Phoenix is a collaboration between Holcim, Block Research Group at ETH Zurich, Zaha Hadid Architects Computation and Design Group and incremental3D. 

From Striatus to Phoenix 

circular construction

Phoenix stands solely through compression, without reinforcement, with blocks that can be easily disassembled and recycled. Image credit: Block Research Group

Building on the innovations of the Striatus Bridge, Phoenix is constructed from 10 tons of recycled materials, including recycled aggregates from the original blocks of Striatus. Using its ECOCycle® circular technology, Holcim developed a proprietary concrete ink for Phoenix that incorporates an optimised low-carbon formulation with a 40% lower CO footprint compared to the 2021 Striatus Bridge, and an overall carbon footprint that is 25% lower than the original structure. 

50% material reduction 

Circular construction, using computational design and 3D printing, allows for a reduction of up to 50% of the materials used with no compromise in performance. Circular by design, Phoenix stands solely through compression, without reinforcement, with blocks that can be easily disassembled and recycled.
Edelio Bermejo, head of global research and development (R&D) at Holcim, describes the common goal: “Demonstrating that essential infrastructure can be designed and built in a way that is circular and low-carbon today.” 

circular construction

Holcim developed a proprietary concrete ink for Phoenix, with an optimised low-carbon formulation that has a 40% lower CO₂ footprint compared to the original Striatus. Image credit: incremental3D

Deconstruction and reuse 

“Concrete is an artificial stone, and like stone, it does not want to be a straight beam, it wants to be a masonry arch,” says Philippe Block, co-director of Block Research Group at ETH Zurich. Following these historical principles, the materials can be kept separate for easy recycling, and to dry-assemble the structure for easy deconstruction and reuse. 

3D concrete printing allows for the material to be used only when, and exactly where, needed. The result is a sustainable and truly circular approach to concrete construction. 

Improved technology 

Phoenix is a significant milestone in technology readiness. It showcases the maturation of integrated design to construction technologies that were initiated with Striatus. 

Shajay Bhooshan, head of Computation and Design Group at Zaha Hadid Architects, explains that there have been improvements in the robustness of the digital design tools, and closer alignment with the numerous structural design and circularity-related improvements. Other improvements include tighter integration with robotic concrete printing parameters and extensive calibration to improve the efficiency of production of almost double the number of blocks in less printing time. 

Design principles 

Thanks to its design principles, Striatus already represented 3D concrete printing in its purest form. Now, after two years and in its second iteration, Phoenix adds a largely reduced carbon footprint and permanence according to building codes, along with many other further improvements. 

Johannes Megens, co-founder of incremental3D, says the team is very excited about Phoenix and is looking forward to many other projects that will evolve in a similar spirit.   

Issue: What does a 3D-printed concrete bridge mean for the future? 

Solution: Phoenix is a showcase of reduced materiality (up to 50%) and a testament to a low-carbon and circular built environment. 

Acknowledgement and thanks go to: for the information in this article.

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