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

基于DFG之前的项目“通过选择性粘合的自由形式混凝土建筑元件的增材制造”在优先计划1542“混凝土轻”的框架内取得的可喜成果，该项目的目标是将3D打印方法选择性水泥活化从基础研究阶段转移到原型阶段，适用于建筑行业。这将是第一次有可能通过这种技术生产具有相应强度和尺寸的混凝土构件。选择性水泥活化方法的特点是将由水和适当添加剂组成的流体施加到由细骨料和水泥组成的干燥颗粒床上，以局部硬化结构。在之前的DFG项目中，已经获得了关于材料和工艺技术的深刻知识，可以用于生产实验室规模的元件，具有结构相关强度，良好的表面分辨率和形状精度。因此，我们制作了一些小物件，以展示在没有任何支撑结构的情况下生产高度复杂和悬垂元件的可能性，这些元件通过普通技术（如模制混凝土或3D打印挤出技术）是不可行的。由工业合作伙伴Progress设计和生产的大型3D打印机原型，其构造空间约为（l x w x h）4.5 m x 2.5 m x 1.0 m。这种3D打印机将能够以真实的规模制造定制的自由形式元素，例如通量优化，轻型结构或原位模板。通过材料技术的进步，将能够制造室内和室外的主要结构。此外，将定义大规模3D打印系统中材料技术和打印后处理的适当组合的一般设置。因此，特别关注的是材料的各向同性特性和层结合。最后，通过新开发的应用概念和详细设计，将使选择性水泥活化在建筑行业中的使用变得容易。除了强调非钢筋结构的生产外，还将首次开发并在原型中实现随后安装和外部预应力钢筋的应用概念。

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.