Interlayer cohesion in 3D printed concrete: The role of width-to-height ratio in modulating transport properties and pore structure

Abstract

Due to the extrusion-based printing and layer-to-layer deposition characteristics, the interlayer cohesion of 3D printed concrete is highly sensitive to the geometry of the printed layers, significantly influencing both mechanical performance and long-term durability. In this study, the width-to-height (W/H) ratio was employed as a geometric parameter to explore its relationship with interlayer transport and pore morphology. The research began by optimizing mix proportions through fluidity and printability tests. Subsequently, chloride ion permeation, mercury intrusion porosimetry, and micro-CT were used to analyze interfacial transport and pore distribution, revealing the influence of the W/H ratio on these properties. The results demonstrate that the W/H ratio plays a crucial role in densification and interfacial defect formation in 3D printed concrete. While the extrusion process enhances matrix compaction, a higher W/H ratio generally promotes stronger interlayer cohesion and reduces chloride ion permeability. However, an excessively large W/H ratio, especially when coupled with air entrainment, can introduce defects and increase porosity at the layer interfaces. The study concludes that maintaining a W/H ratio between 1.5 and 2.0 effectively strengthens interlayer cohesion. These results offer valuable theoretical insights and technical support for the design and application of 3D printed concrete materials.