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Povzetek: This research proposes an alternative low-cement multicomponent binder for extrusion-based 3D concrete printing to reduce CO2 emissions associated with high Portland cement content. Due to the extremely low Portland cement content (100 kg/m3), the proposed mixture presents several limitations, making it unsuitable for 3D printing without additional activation. To overcome these limitations, chemical and physico-chemical activation methods were applied to promote rapid early-age structuration, partly associated with accelerated ettringite formation, thereby improving compliance with the printing process requirements. The results demonstrate that both activation methods positively affect Portland cement hydration and improve printing-related properties. The research focuses primarily on the hardened properties of 3D-printed concrete, showing that activation reduces macroscopic porosity and increases density and compressive strength. The applied activation methods also increase overall shrinkage compared to the nonactivated low-cement mixture. However, the absolute shrinkage remains approximately 25–30 % lower than that of a conventional reference mortar with a high Portland cement content. The suitability of the components used in the multicomponent binder was evaluated through pozzolanic activity testing. In contrast, the effects of chemical and physico-chemical activation on binder phase composition were investigated by X-ray diffraction, and the hardened properties of concrete were assessed using X-ray computed tomography, mercury intrusion porosimetry, shrinkage measurements, density, and compressive strength testing. The results demonstrate that chemical and physico-chemical activation enables the effective use of low-cement multicomponent binders in extrusion-based 3D concrete printing, providing a more sustainable alternative to conventional high-cement mixtures.
Ključne besede: 3D-tiskanje betona, večkomponentno vezivo z nizko vsebnostjo cementa, kemična aktivacija, fizikalno-kemična aktivacija, krčenje, 3D concrete printing, low-cement multicomponent binder, chemical activation, physico-chemical activation, shrinkage
Objavljeno v DiRROS: 15.05.2026; Ogledov: 164; Prenosov: 122
Celotno besedilo (4,77 MB)
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Povzetek: This study investigates the fresh state and hardened state mechanical and durability properties of 3D-printed concrete. The mechanical tests focused on its anisotropic behavior in response to different load orientations. Compressive, flexural, and splitting tensile strengths were evaluated relative to the print layers orientation. Results showed that compressive strength varied significantly, achieving 85% of cast sample strength when the load was applied parallel to the print layers ([u] direction), 71% when the load was applied perpendicular to the print object’s side plane ([v] direction), while only reaching 59% when applied perpendicular to the top plane ([w] direction). Similar trends were observed for flexural strength, with average values reaching 75% of cast sample strength when the load was applied perpendicular to the print layers ([v.u] and [w.u] directions), but decreasing to 53% when the load was applied parallel to print layers ([u.w] direction), underscoring the weaknesses at interlayer interfaces. The splitting tensile strength remained relatively consistent across print orientations, reaching 90% of the cast sample strength. Durability assessment tests revealed that 3D-printed concrete exhibits reduced resistance to environmental factors, particularly at the layer interfaces where the cold joint was formed, which are prone to moisture penetration and crack formation. These findings contribute valuable insights into the mechanical and durability properties of 3D-printed concrete, emphasizing the importance of print orientation and interlayer bonding in its performance. This understanding helps guide the optimal use of 3D-printed elements in real-life applications by aligning load or exposure to environmental factors with the material’s strength and durability characteristics.
Ključne besede: civil engineering, 3D-printing, concrete, additive manufacturing
Objavljeno v DiRROS: 11.02.2025; Ogledov: 3604; Prenosov: 770
Celotno besedilo (6,94 MB)
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