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来自TU Braunschweighave presented a novel type of 3D printing process that could potentially push the limits of additive manufacturing in the construction sector, called Injection 3D Concrete Printing (I3DCP) in suspension.
在混凝土结构中，当前的添加剂制造技术倾向于通过材料挤出，喷射或结合来侧重打印。尽管这些技术具有其优点，但它们可以被几何分辨率和复杂性，表面质量和低建筑物速率的缺点所抵消。
悬浮液中I3DCP的基本思想是通过将一种流体材料注入另一种流体材料来克服分层3D打印的局限性。由于每种材料的特定流变特性或它们如何响应力或应力，这会产生稳定的结构。
According to the researchers, this method offers higher building rates and the ability to print freeform trajectories that are not constrained by gravitational forces. As such, I3DCP could establish entirely new structural features and efficiencies for 3D printed concrete structures.
I3DCP in suspension applications
The first large-scale application of I3DCP was presented by French start-up Soliquid, which extruded concrete into a reusable gel matrix using a 6-axis robot to create a large-scale 2.5-ton artificial coral reef. No support structures were needed as the gel kept the component in position throughout the printing process until it had hardened and could be removed.
In the same year, an experimental design studio was set up at TU Braunschweig to design and produce small-scale spatial structures with I3DCP technology. Instead of using a gel, however, the researchers began experimenting with the use of a ground limestone suspension as the carrier liquid.
While the first applications of the technique have shown promise, more knowledge of the rheological requirements of injected concrete and the carrier liquids are required to move the technology forwards into industrial-scale applications. The researchers are also looking at the recyclability of the carrier liquid and its economic and ecological impacts.
Overcoming challenges of the I3DCP process
I3DCP工艺的成功取决于注射混凝土材料（a）的重量之间的微妙平衡，注入其注入的载体液体的浮力（b），印刷喷嘴的力和两种材料的流变特性。如果没有达到这些力之间的适当平衡，则将导致形状不可思议的物体。
与此同时,形状of the 3D printed structure is determined by the extrusion flow rate, the velocity of the robot-guided nozzle, and the cross-sectional area of the nozzle.
地面石灰石被认为是可重复使用且便宜的惰性填充材料。根据Tu Braunschweig团队的说法，地面石灰石悬架在成本，可重复使用和控制流变特性方面具有优于凝胶的优点。
To overcome the challenges of I3DCP in suspension and to test the effectiveness of their technique, the researchers conducted multiple experiments using a lightweight UR 16 robot. Three formworks were placed on two adjacent sides of the robot table and six molds were filled with the ground limestone suspension. The robot then extruded the concrete into the molds at a rate of 0.000025 m³/s.
The resulting reinforced I3DCP printed elements formed a scaled version of an arch-shaped truss bridge, which the researchers claim shows great potential for novel lightweight concrete structures. Unlike the layer-by-layer deposition of horizontal strands inherent in most 3D concrete printing technologies, the team was able to produce intricate concrete structures by printing spatially free trajectories that are not restricted by gravitational forces during printing.
Going forwards, the Braunschweig team will seek to advance their I3DCP technique by adjusting the strand diameter of the injected concrete via controlling its variable force flow. This, they believe, could see the establishment of an “entirely new, previously unseen tectonic language” and improved structural efficiency for building concrete structures.
研究中的更多信息可以在标题为：“Injection 3D concrete printing in a carrier liquid – Underlying physics and applications to lightweight space frame structures,”发表在《水泥与复合杂志》杂志上。该研究由D. Lowe，A。Vandenberg，A。Pierre，A。Thoman，H。Kloft和N. Hack合着。
Recent advances in concrete 3D printing
Concrete 3D printing technologies can deliver substantial cost and lead time benefits compared to conventional construction techniques. The technology can also yield sustainability benefits, with construction firms potentially able to cut their related waste by up to 60 percent byrecycling additive manufactured formwork, such as that developed byBigRep和BASFsubsidiaryForward AM。
Recent research into 3D printable construction materials has enabled scientists from the斯威本技术大学和河北工业大学to turn recycled concrete aggregate, ceramsite particles, and desert sand into a低成本挤出建筑材料。新的3D打印材料可能有可能在重型建筑应用中使用。
Elsewhere, researchers fromRMIT Universityin Australia have sought to make 3D printed concrete structures stronger by从龙虾壳图案中汲取灵感, whileUC Berkeleyscientists have explored incorporating3D打印的聚合物八位晶格into concrete structures to reinforce them.
Most recently, architects and engineers fromETH Zurich’s Block Research Group创建了所谓的first 3D printed concrete bridge built without reinforcement。Stable thanks only to its geometry, the bridge is formed from a newly developed concrete that is printed at specific angles in blocks that are self-supporting.
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特色图片显示printing around pre-installed steel reinforcement bars using the I3DCP process. Photo via TU Braunchsweig.
