# Smart Infrastructure and Additive Manufacturing: Synergies, Advantages, and Limitations
## 3 Key Applications of 3D Printing in Smart Infrastructure
### Modular and Prefabricated Components  
Bicycle and pedestrian bridge building is one of the most outwardly visible and innovative uses of 3D printing to the infrastructure, which demonstrates the radical potential of the technology in current engineering. The Netherlands' world's first, fully operational, 3D-printed concrete bridge, launched in 2018--a purpose-built bridge intended for cyclists--was a breakthrough demonstration of such innovation [66; 67]. Eindhoven University of Technology and the construction company BAM Infra collaborated on this historic project in the municipality of Gemert, demonstrating the synergy between academic research and industry in advancing construction technologies. The bridge, which is around 8 m long, was built using a patented 3D printing method that precisely and automatically layered pre-stressed, high-strength concrete. In contrast to conventional bridge building techniques, which frequently need formwork and a great deal of physical effort, this method made it possible to create a highly optimized structure with complex geometric patterns. By more evenly dispersing loads and using less material overall, these patterns improved the bridge's structural efficiency in addition to improving its visual appeal. Hence, the project confirmed the environmental advantages of additive manufacturing in construction and adjusted to sustainability goals by achieving material wastage savings on a substantial scale. Additionally, the 3D-printed Gemert bridge was built with loads between 5 tons, or the weight of two trucks, in an attempt to achieve extreme security and durability requirements. This accomplishment confirmed that 3D printing is an attainable process for the manufacture of durable infrastructure elements. Figure 4 depicts the aforementioned 3D-printed Gemert bridge [103]. Similarly, the construction of a 3D-printed concrete footbridge in Zhaozhou, China, in 2021 marked a major turning point in the use of 3D printing technology in infrastructure [68; 69]. At the time, this project--which measured 28.1 m in length and 3.6 m in width--was among the biggest and most ambitious uses of additive manufacturing in the field of civil engineering. Advanced robotic 3D printing methods were used in the design and construction of the bridge. These systems used a layer-by-layer deposition procedure to generate a monolithic concrete structure that was structurally optimized. This method demonstrated how 3D printing has the ability to completely transform large-scale structural applications by doing away with the necessity for conventional formwork and drastically lowering material consumption. In order to ensure effective weight distribution and structural integrity, topological optimization techniques were incorporated into the design of the Zhaozhou footbridge, which was constructed to fulfill strict safety and performance standards. Complex geometric features, including internal lattice structures, might be integrated via 3D printing, improving the bridge's strength-to-weight ratio while using fewer raw materials. A specially designed concrete mix for extrusion-based 3D printing was also used in the project; this mix outperformed regular concrete in terms of durability and mechanical qualities. The Zhaozhou bridge project demonstrated the environmental benefits of 3D printing in construction from a sustainability standpoint. The project significantly reduced its carbon footprint by removing the requirement for formwork and lowering material waste. The utilization of recyclable elements in the concrete mix was also made possible by the accuracy of the 3D printing process, which further aligned the project with sustainable development and circular economy ideas. Figure 5 depicts the aforementioned bridge. Figure 4: The 3D-printed Gemert bridge in the Netherlands [103]. Figure 5: The 3D-printed concrete footbridge in Zhaozhou, China.