3D PRINTING ARCHITECTURE - Open Framework for Binder Jetting in Construction

Abstract

The construction sector stands at a critical juncture, facing the dual challenges of increasing productivity and reducing environmental impact. Over the next 30 years, the world’s building stock is anticipated to double in response to the growing urban population, while the industry is also expected to achieve "net-zero carbon" within the same timeframe. The strategies to address these challenges will significantly affect global sustainability and urban development. Automation emerges as a critical factor for enhancing productivity. Manufacturing and agriculture have grown exponentially by integrating automation technologies, unlike the construction industry, which has seen limited advancement in productivity over the past half-century. Automation in construction presents three key opportunities: the use of robotics for traditional on-site activities such as bricklaying and road paving; the automation of modular construction and 3-D printing of building components; and the digitisation and automation of design, planning, and management processes to enhance efficiency on construction sites. This dissertation focuses on the automation of modular construction through 3D printing, utilising digital modelling and planning tools to open new paths for research. The emerging domain of additive manufacturing (AM) is increasingly impacting the construction industry, with advanced machines facilitating the accurate production of large-scale components. This innovative approach enables distinct aesthetic and structural possibilities, promoting efficient building practices that could significantly reduce material use. However, realising these ambitions requires addressing the limitations of current AM technologies, such as enhancing the printed parts' durability and mechanical integrity, evaluating and minimising both the economic and environmental costs of the materials used, and increasing the scalability of the printing process to meet industrial demands. Current implementations in research can be distinguished in two streams depending on whether the 3d printed parts are used directly as building parts or indirectly as formwork or moulds. This thesis investigates the potential of Binder Jetting (BJT) for the direct fabrication of architectural components, focusing on the development of an open fabrication framework to enhance its application in construction. "Open" in this context signifies a modular and extensible approach to hardware and software, characterised by manufacturer-independent components and communication protocols. By exploring alternative materials and technologies, this research endeavours to refine BJT as a method tailored for construction, leveraging additive manufacturing's advantages to enable innovative, sustainable, and cost-effective architectural solutions. Central to this study is exploring BJT's ability to produce large-scale parts accurately and efficiently. Starting with the conventional configuration of industrial BJT systems, the research proposes a novel implementation of its core components within a modular and adaptable fabrication framework aimed explicitly at facilitating comprehensive material research. A pivotal achievement of this research is the successful integration of alkali-activated inorganic binders, commonly called geopolymers. Through the systematic refinement of both the fabrication process and the printing strategy, the mechanical properties of the printed parts using geopolymer binder jetting (GeoBJT) can now outperform unreinforced C30/37 OPC concrete. This factor and the efficiency obtained regarding production speed and process reliability make the technology effective for architectural projects. Given the interdisciplinary scope of this research, the thesis provides detailed technical insights into the development process, the methodologies employed, and the evaluation of the results achieved. The practical application of this research is exemplified through prototypes, including the fabrication system realised in a prototypical 3D printer model, alongside three illustrative case studies. The first case study elaborates on the direct fabrication of monolithic artefacts. The object of production discusses the ability of the system to render bespoke end-user designs with complex geometries using geopolymer binders and recycled aggregates. The second case study focuses on the structural use of the presented technology by producing the discretised parts of a funicular floor design. The prototype shows the results obtained regarding the accuracy and repeatability of the printing process. This case study also introduces an innovative approach to on-site digital manufacturing, exemplified by deploying a portable 3D printing setup to a quarry in Ticino, Switzerland, highlighting the method's potential for localised material sourcing. The third case study discusses the comparative analysis between different material mixes, observing the ability of the technique to diversify the qualities of the produced parts by tailoring aspects such as particle type and size distribution. In summary, this thesis contributes to the evolution of construction and digital fabrication by developing a comprehensive BJT-based framework for the sustainable and innovative production of architectural elements. Its interdisciplinary approach, combining engineering, material science, and architectural design, establishes a new pathway for additive manufacturing in construction and lays the foundation for future research.