Industrial 3D Concrete Printing by Selective Cement Activation - Process, Material, Applications

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Based on the promising results of the previous DFG project "Additive manufacturing of free form concrete building elements by selective binding" within the frame of the priority programme 1542 "Concrete light", it is the aim of the project to transfer the 3D-Printing method Selective Cement Activation from the stage of basic research into a prototype stage, applicable in construction industry. For the first time, it will be possible to produce concrete elements with relevant strength and size for construction by means of this technique.The selective cement activation method is characterized by applying a fluid, consisting of water and additives where appropriate, onto a dry particle bed, consisting of fine aggregates and cement, to locally harden the structure. In the preceding DFG project, a profound knowledge concerning material and process technology which can be used to produce elements in laboratory scale with constructional relevant strength, good resolution of the surface and shape accuracy has already been achieved. Therefore, small objects were produced to demonstrate the possibility of the production of highly complex and overhanging elements without any supporting structures, not feasible by means of common techniques such as moulded concrete or 3D-Printing extrusion techniques.As a result of the transfer project, a large scale 3D printer prototype with a construction space of approximately (l x w x h) 4.5 m x 2.5 m x 1.0 m designed and produced by the industrial partner Progress shall be available. This 3D printer will be able to manufacture customised, free form elements in real scale such as flux optimized, light structures or stay-in-place formworks. Through the progress in material technology, manufacturing of indoor and outdoor primary structures will be enabled. Furthermore, a general setup for appropriate combinations of material technology and post-printing-treatment in large scale 3D-printing systems will be defined. Therefore, special focus is on the isotropic properties of the material and on layer bonding. Finally, an easy access for the usage of the Selective Cement Activation in construction industry shall be enabled by newly developed application concepts and detail designs. Besides the emphasis on the production of non-reinforced structures, for the first time concepts for the application of subsequently installed and externally pre-stressed reinforcement will be developed and realised in a prototype.