Shotcrete 3D printing

Shotcrete 3D printing is an additive construction process in which successive layers are sprayed onto the build surface by a compressed-air nozzle rather than extruded as a filament.

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Shotcrete 3D printing is an additive construction process in which the material is sprayed onto the build surface through a compressed-air nozzle rather than extruded as a filament. The impact energy of the jet compacts each layer against the one below it, so the process combines the geometric control of printing with the placement behaviour of sprayed concrete. Much of the published development work comes from German research groups, and the process is still closer to research and pilot use than to routine site practice.

In practice

The main reported advantages are denser layers and better bond across the interface than free extrusion gives, and the ability to spray onto an existing surface or around reinforcement that has already been placed, which opens a route to conventionally reinforced printed elements. Layer geometry is less sharply defined than in extrusion, so the nozzle distance, spray angle and traverse speed have to be controlled together. The drawbacks are rebound and overspray, which waste material and require collection, a rough surface that usually needs finishing, and the need for an enclosed working area because of dust and spray drift.

Related terms

  • Interlayer bond — the adhesion between layers, which spraying tends to improve.
  • Reinforcement strategies — the methods for placing steel or fibres in printed elements.
  • Surface finish — the treatment of the printed face, more often required after spraying.

Related

Interlayer bondInterlayer bond is the adhesion between two successive printed layers, usually the weakest plane in a 3D printed concrete element.Reinforcement strategies in 3D printingReinforcement strategies are the methods used to give printed concrete tensile capacity, and they remain the least settled aspect of 3D concrete printing.Surface finish of printed concreteSurface finish is the condition of a printed element's face, from the ribbed as-printed texture to troweled, ground, rendered or coated surfaces.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.