Upscaling earth formworks: 3D printing strategies for material optimised reinforced concrete structures

Abstract

There is a growing need to understand how locally sourced earthen materials can be processed to build more efficiently and sustainably. Earthen formworks combined with 3D printing technologies present a unique opportunity for the concrete construction sector to address the wastefulness and complexity of custom formworks. The current state-of-the-art projects in academia and industry demonstrate that earthen formwork strategies effectively address this challenge, but remain burdened by upscaling issues such as production speed. This research bridges the gap by exploring strategies for 3D Printed earth formworks to efficiently produce structural elements using custom self-compacting and set-on-demand concrete mixtures. A first base earth mix is developed for reduced shrinkage and later modified via a plasticizer for increased green strength, forming the final mix. Two mix iterations are deployed in two corresponding strategies where concrete is cast into the earth formwork in a dry or plastic state. The methods highlighting the setups for 3D printing and procedures for appropriate material processing such as slump flow, shrinkage and rheology are presented. The results are explored via two column prototypes leading to a final demonstrator for a 2 m high reinforced concrete column. Conclusions are drawn on the implications of the two casting strategies, the current persisting challenges and the crucial next steps for development. Thus, the research provides a foundation for how clay formworks can be upscaled effectively for more sustainable production of complex concrete structures.