Computational Design for 3D Concrete Printing

QC 20260520

Abstract

The transition from conventional cast concrete to 3D Concrete Printing (3DCP) representsa paradigm shift in concrete technology, replacing formwork-based shaping with the direct,layer-wise deposition of fresh concrete according to a digital model. This technologyexpands the scope of concrete construction, particularly by enabling the fabrication ofinnovative, complex geometries within an automated process. Beyond formal capabilities,the process’s inherent digitalisation minimises manual labour, improves productivityand workers’ safety, and streamlines interactions among stakeholders, thereby reducinghuman error and improving construction quality. Despite sustained progress in printingmaterials and equipment, systematic methods for exploiting design capabilities remainunderdeveloped. This limitation largely stems from the assumed separation between thedesign process and the generation of manufacturing instructions.This thesis aims to extend the design scope of 3DCP by treating the toolpath as thedesign object, thereby serving as the primary link between computational design androbotic fabrication. To this end, the research develops and validates integrated design-tomanufactureworkflows for manipulating, analysing, and optimising print paths, whileaccounting for material and process constraints. Methodologically, the research is situatedat the intersection of architectural design and architectural engineering, with a focuson computational design and control for 3DCP. Workflows are refined iteratively throughsimulation, digital prototyping, and fabrication tests. Structural and steady-state thermalsimulations are integrated within the same software environment, and the results aremapped back to geometry and toolpaths. This thesis presents a computational designframework based on low-level geometric operations to enhance structural and thermalperformance and to grade properties along the printed part accordingly. By translatinganalysis-informed fields into corresponding modulations of printing parameters, thework explores methods for material optimisation and the creation of functional gradientsthroughout the printed element. This enables the broadening of design possibilities,optimisation of printing parameters, and structural optimisation within the inherentrestrictions of the process.The conceptual foundation for the grading work is established through a reviewof functionally graded materials (FGMs) applied to 3DCP (Paper I), which identifiesthree routes to functionally graded concrete: variable mixing ratios, variable additionof particles, and varied densification. This thesis operates within the third route,where grading is achieved through the spatial arrangement of deposited material atthe mesoscale rather than through changes in material composition. The contributionsinclude integrated workflows for print-path manipulation as a primary design operation,progressing from surface-level property control via variable filament width (Paper II)to stress-informed internal material distribution via topology optimisation (Paper III). Laboratory testing of topology-optimised unreinforced 3DCP beams reveals a substantialincrease in load-to-weight ratio compared to a conventional triangular infill reference.These methods are extended to macroscopic porosity through procedural print patternsthat create porous, permeable structures at the filament level (Paper IV). They are alsoapplied to spatial grading through a guide-surface mapping technique that assigns printingparameters as a continuous field, regardless of the underlying geometry (Paper V). Anapplication case investigates hybrid façade elements that combine reused precast concretewith additively manufactured skins, reducing the expected thermal transmittance bynumerical simulations while maintaining constant material use (Paper VI).Taken together, the results demonstrate that the design scope of 3DCP can be extendedfrom shape specification to the control of mesoscale material properties, enabling gradedstructures with improved structural and thermal performance within the constraints ofcontinuous extrusion.

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