Tectonics of Concrete Printed Architecture: Technology, Components and Assemblies for Column-Slab Construction

Abstract

Despite its many virtues, reinforced concrete causes the most pollution in the building industry. In this context, digital fabrication with concrete emerges as an increasingly relevant research field aiming to lower the environmental impact of concrete. 3D Concrete Printing (3DCP) is the globally dominant digital fabrication technology with concrete. Its accelerated development and increase in popularity are rooted in the premise that no-waste construction is achievable through lean building practices and customisation. However, this technology so far did not fully deliver its sustainability promise. This failure is partly due to technological limitations, but another reason is the lack of coherent design and fabrication strategies compatible with the 3D printing process. Driven by the ambition to improve the sustainability and scalability of 3DCP, the core aim of this doctoral dissertation is to formulate, implement, and assess the fundamental tectonic principles for building meaningful structures under current standards and regulations. For maximum impact, the scope of the research is defined around studying column-slab construction, with ribbed slabs for a significant material reduction. Defining tectonics in the novel context of 3DCP pursues a bottom-up approach that starts from the extruded filament and scales up to the assembly of 3DCP components. This tectonic roadmap serves as a practical guide for identifying the potential and limitations of 3DCP. Such an approach is addressed to a professional audience from the architecture, engineering, and construction sector. This dissertation presents contributions to the three topics mentioned above, essential to layered extrusion: technology - meaning how to process the material; components - deciding how to deposit the extruded filament; assemblies - determining how to segment and connect the components. The 3D printing technology utilises a fast-setting concrete obtained by intermixing a base mortar with an accelerator inside the printing nozzle. Technology development was design-driven, meaning that aesthetic qualities, 3D printing resolution, form, and surface patterning, were prioritised. The constituent building components of column-slab structures - columns, shear walls, and slabs - were prototyped with the developed 3D printing system. These elements incorporate hollow channels for rebar insertion, component-specific utilities, and custom-designed patterns on the exposed concrete surfaces. Subsequently, multiple components were assembled, focusing on layer continuity between adjacent components. As a final step, in situ conventional reinforced concrete connects all the 3DCP elements into a monolithic structure. The results obtained for each domain-relevant area - technology, components, and assemblies - contribute to defining the essential practical and theoretical aspects of 3DCP tectonics. Thus, the concrete filament becomes the discrete unit that interrelates the previously introduced fields bridging their specific scales, physical and chemical properties, design, and production.