Simultaneous Reinforcement of Concrete While 3D Printing (2020-07)¶

In order to fully realize the disruptive nature proposed by concrete printing for the construction industry, key challenges need to be overcome to enable the scaling up of this technology. Chief amongst them is the incorporation of reinforcement to absorb tensile stresses and support the structure not only during the printing and curing but also during its service life. Numerous strategies have been tested that allow for embedding reinforcement in the form of filaments, cables, rods or mesh during and/or post printing. This paper explores a strategy for in-situ printing that attempts to embed discrete U-shaped reinforcement elements “staples” vertically interlocking layers simultaneously while printing. A tool, developed for this purpose, trails the extruder and discharges a reinforcement staple that embeds itself into the printed layers. The staples not only penetrate multiple layers, but also interlock to form a reinforcement matrix in the concrete along the vertical axis capable of absorbing limited amounts of tensile stresses. When subject to a 3-point bending test, the reinforced printed elements exhibited an increase in tensile properties. Nevertheless, further research into shape and size of the reinforcement staple is needed to achieve optimum results. Furthermore, with the assistance of robotic fabrication strategies, every position within the print geometry can be identified accurately and reinforcement can be positioned precisely. These positions and their properties/states can be informed by simulating the performance of the geometry under load conditions. The ability to place reinforcement discreetly and accurately can help localize the reinforcement to key stress areas within the geometry thereby optimizing its performance and the use of material.