Orientation and spatial distribution of pores and fibers in concrete elements produced by extrusion-based 3D printing

Abstract

Use of short dispersed fibers has been considered a promising solution to address the challenge of integrating reinforcement into 3D concrete printing. This study used micro-CT scanning technology to examine pore and fiber orientations and their spatial distribution of single-filament and multi-filament specimens extruded using various nozzle shapes and standoff distances. Results show that nozzle pressing and gravity-induced lateral flow progressively collapsed and filled voids in lower layers, leading to a pronounced porosity gradient along the build height. A smaller standoff distance enhanced the fiber alignment along the printing direction as the nozzle exhibited higher pressure upon de..