A robotic twist that makes concrete to crack resist

Concrete is a quasi-brittle material that suffers from resistance to cracking. The research details a nature-inspired design that significantly improves damage resistance (fracture toughness) in robotically manufactured concrete components by 63% compared to conventional cast unreinforced concrete.
The study draws inspiration from the scales of the ancient coelacanth fish, which represents a rare double-helical design, also known as double-bouligand architecture. This architecture consists of helically arranged collagen fibrils in a bilayer, providing the fish scales with remarkable damage tolerance. Moini lab has engineered this design in concrete by arranging it into individual strands and stacking them in a double-bouligand pattern. This innovative design leads to several toughening mechanisms that improve the resistance to cracking. These mechanisms work to shield cracks from propagating, deflect cracks from a straight path during the propagation, and interlock the fractured surfaces after propagation, all of which synergistically and significantly enhance the material’s overall damage resistance.
One essential tool for engineering and forming these designs relies on discretized layer-by-layer and strand-by-strand additive manufacturing processes. Using advanced robotic additive manufacturing (3D-printing) with concrete techniques developed at Moini Lab, the fabrication of these double-helical arrangements was made possible as detailed in the Article’s Supplementary Information. This additive manufacturing process and their corresponding algorithms for robotic path generation enable the study of new designs of materials and structures.  Using large industrial robots, this study highlights the possibility of scaling up the fabrication of stronger concrete by extending the fabrication of a broad range of architected materials to full structural scales. One of the key challenges in fabricating such intricate designs is the tendency of fresh concrete to deform under its weight, which can compromise the precision of the structure. To overcome this, the study developed a customized extrusion system that controls the hardening rate of the concrete. This advanced system, integrated into the robot’s nozzle, combines concrete with a chemical accelerator before extrusion. This ensures rapid curing and maintains the geometric integrity of the architected concrete during the fabrication process.
This work not only opens new avenues for improving the mechanical properties of concrete but also highlights the potential of biomimicry and advanced manufacturing technologies in developing advanced civil infrastructure and building components.
The research was supported by the National Science Foundation CMMI Advanced Manufacturing Program (Award # 2217985). The paper, titled “Tough Double-Bouligand Architected Cementitious Material using Robotic Additive Manufacturing,” was published on August 29, 2024.