PVA-Fiber-Reinforced High-Strength Cementitious Composite for 3D Printing (2021-11)¶

Three-dimensional (3D)-printed concrete is a highly promising construction material that will allow for the realisation of formless construction and digital design. The constructability, mechanical properties, and durability of the matrix have a determining effect on the structural applicability of the concrete. In this study, to alter the brittle failure mode of common printed concrete, polyvinyl alcohol fibres were incorporated into a cementitious printing ink. The mix proportion was optimised based on the construction requirements in terms of the flowability, setting time, stacking stability, and load-bearing capacity. Next, the effects of the printing and loading paths on the mechanical properties and durability were investigated experimentally. Computed tomography (CT) imaging was employed to determine the defect distributions of the 3D-printed samples as well as the mechanisms responsible for the observed differences in their mechanical properties and durability. The CT images showed that a greater number of defects were present between the adjacent strips than between the layers. This microscale heterogeneity induced macroscale anisotropy in the printed samples. Further, the printing and loading paths also affected the mechanical properties and durability of the samples. The flexural strength was more sensitive to the interfacial defects as compared to the compressive strength. The stacking-up method is better suited for increasing the density of the printed matrix, resulting in greater chloride ion penetration at the interface than is the case for the matrix, which is affected by the interfacial defects.