Reinforcement strategies in 3D printing

Reinforcement strategies in 3D concrete printing are the methods used to give a printed element tensile and shear capacity, since the printing process itself leaves no room for a conventional reinforcement cage.

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Reinforcement strategies in 3D concrete printing are the methods used to give a printed element tensile and shear capacity, since a moving nozzle cannot deposit material through a conventional reinforcement cage. Concrete is weak in tension, so the question of how steel or fibre enters a printed element decides whether that element can carry load at all.

In practice

Several approaches are in use or under research. Printed skins can serve as permanent formwork, with conventional bars placed in the cavity between them and the cavity then filled with ordinary concrete. Bars or mesh can be laid into the print between layers, or entrained during printing, at the cost of interrupting the path. Fibres can be mixed into the mortar, which improves toughness and crack control but does not replace designed reinforcement. Tendons can be threaded through printed ducts and stressed after hardening. External reinforcement can be applied to the finished surface. None of these is covered by a complete design code, which is why most printed structures today are either non-structural or verified by project-specific testing.

Related terms

  • Post-tensioning — stressing tendons after the concrete has hardened.
  • Interlayer bond — the plane where printed elements are usually weakest in tension.

Related

Post-tensioningPost-tensioning compresses a hardened concrete element by stressing tendons through it, and is one workable route to reinforcing printed parts.Interlayer bondInterlayer bond is the adhesion between two successive printed layers, usually the weakest plane in a 3D printed concrete element.3D Concrete Printing3D concrete printing builds elements layer by layer without formwork. How extrusion, particle-bed and shotcrete methods work, and where the limits are.3D Printed Wall SectionsPrinted concrete walls: single and double skin, cavities and insulation, partitions, garden and retaining walls, and the reinforcement questions.