Abstract
The construction sector is undergoing a period of transformation as digital technologies reshape established practices. Among these, three-dimensional concrete printing (3DCP) has gained prominence for its potential to reduce reliance on formwork, minimise material waste, and introduce greater design freedom. Yet, the pathway to broader adoption remains complex. Printable concretes must simultaneously meet fresh-state requirements for extrusion and buildability, hardened-state mechanical performance, and long-term durability, while also addressing sustainability concerns arising from high cement demand. This thesis adopts an integrated approach that combines literature studies, database analysis, experimental investigations, and environmental assessments to evaluate how material properties and mixture optimisation strategies influence printability, structural performance, durability, and sustainability in 3DCP. The work is structured around five objectives: mapping the role of digital technologies and 3D printing in construction; identifying key parameters governing printability, rheology, and mechanical reliability; evaluating the influence of material modifications (binders, aggregates, admixtures, and fibres) on mixture performance; analysing durability behaviour under environmental stressors; and linking these findings to life-cycle sustainability trade-offs. A series of systematic literature studies established the contextual framing of 3DCP, highlighting critical research gaps, particularly in durability and long-term performance. Building on this, a database of over one thousand printable mixtures was developed to examine the effects of sand-to-binder and water-to-binder ratios, admixture use, and rheological properties across different printing scales. Zone-based analysis revealed distinct relationships between mixture design and printability windows, underlining the decisive role of yield stress, viscosity, and structuration rate. Laboratory-scale experimental work complemented these insights by testing the effects of hydrated lime, tile powder, and accelerators on dual-phase optimisation of mixtures, ensuring both extrusion feasibility and post-print stability. Results demonstrated trade-offs between printability, shrinkage, and strength, while an optimised composition achieved improved interlayer bonding, toughness, and reduced material demand. The durability dimension was addressed through database-driven studies, showing that moderate binder replacement and incorporation of supplementary cementitious materials, such as rice husk ash, enhance resistance against freeze–thaw cycles, chloride ingress, and carbonation, while simultaneously reducing CO₂ emissions by up to 40%. By systematically linking material design to printability, durability, and sustainability, this thesis provides an integrated basis for balanced mixture optimisation in 3DCP. Its contributions lie in bridging fragmented research domains, providing quantitative insights into mixture behaviour, and offering practical guidelines for developing concretes that are not only printable and mechanically reliable but also durable and resource-efficient. These findings aim to support both academic progress and industrial application, contributing to the responsible adoption of 3DCP in the construction sector.