Abstract
3D concrete printing (3DCP) offers many new possibilities. This technology could increase the productivity of the construction industry and reduce its environmental impact by producing optimised structures more efficiently. Despite significant developments in materials science, little effort has been put in developing reinforcement strategies compatible with 3DCP and on the characterisation of their structural behaviour. Consequently, 3DCD still lacks compliance with structural integrity requirements. This study presents an experimental investigation consisting of nine four-point bending tests on extrusion 3DCP beams reinforced with various types of reinforcement. As interlayer shear reinforcement, aligned end-hook fibres (0.3 and 0.6%) or steel cables (0.1%) placed between the layers of printed concrete were used. As longitudinal reinforcement, unbonded post-tensioning and conventional bonded passive reinforcement were explored. The crack patterns and their associated kinematics were tracked using digital image correlation. The results show that the post-tensioned beams failed in a brittle manner due to the crushing of concrete in bending, with deformations localised in a few bending cracks. In the beams with conventional bonded longitudinal reinforcement, both bending as well as shear cracks were generated, and the brittle failure of the interlayer shear reinforcement limited the ultimate load. Estimations based on the measured crack kinematics show that the interlayer shear reinforcement carried most of the applied shear force. Based on these results, a simple mechanical model is developed to understand the mechanical behaviour and to pre-design the required amount of interlayer shear reinforcement.
Highlights
The building sector, including the construction industry, is one of the primary consumers of energy and emitters of CO2 [1]
This study presents an experimental investigation consisting of nine four-point bending tests on extrusion 3D concrete printing (3DCP) beams reinforced with various types of rein forcement
The 3DCP process used in this study is based on the set on-demand method, in which an accelerator activates an Ordinary Portland Cement (OPC) mortar through active mixing performed inside the extruder tool
Summary
The building sector, including the construction industry, is one of the primary consumers of energy and emitters of CO2 [1]. The material needs to be adjusted to be pumpable and only short, flexible fibres, which are typically more expensive and structurally less efficient, can be used Beyond these reinforcement concepts that are closely linked to conventional methods, approaches developed for 3DCP exist. Other studies employ short rein forcing bars inserted perpendicular to the printing direction [34,35,36] For these approaches, the main challenge lies in the discontinuity of the reinforcement and the long lap splicing length required to provide continuity of the different segments. Further research in the field of structural testing is needed to advance the knowledge of the structural performance of reinforced 3DCP elements
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