# Environmentally Friendly Smart Construction--Review of Recent Developments and Opportunities
## 5 Summary and Conclusions  
The construction industry is actively exploring various strategies and approaches to address the challenges of environmental impact, energy efficiency, labour costs, building sustainability and waste reduction. From the research and development that have been  
Figure 7: Topologically interlocked assemblies of osteomorphic blocks [180]. **(a)** Individual block, **(b)** planar assembly, **(c)** corner assembly. reviewed here, the following directions can be identified as the most promising methods regarding the environmentally friendly smart construction:  
Three-dimensional concrete printing (3 DCP) is the first on this list. The 3 DCP has a significant potential for the construction industry by offering (1) architectural design freedom and customization, (2) optimal material utilization through precise material deposition and (3) faster construction times by eliminating the need for formwork and reduction in manual labour. The ongoing research into 3 DCP focuses on improving the structural integrity, scalability and cost-effectiveness of 3D-printed buildings. While considerable progress has been made in the development of design guidelines for 3 DCP, achieving structural certainty and ensuring the long-term performance of printed structures are still open problems. The structural behaviour, durability and long-term properties of 3D-printed elements are not understood as well as those making up conventional concrete. The formulation of printable concrete mixtures and the reliable sourcing of suitable materials impact the performance and durability of printed structures and require further research. The costs associated with 3 DCP that include printers, materials and skilled labour will be reduced after the initial investments into equipment, education and skill development are made. The main challenge of 3 DCP technology remains the implementation of reinforcement. The short-fibre concrete is still brittle and relatively weak in tension, which requires the use of continuous fibres, rebar or cable reinforcement. Various reinforcing techniques that have been proposed for 3 DCP possess different limitations and can be only applied under specific conditions [140]. Among these methods, the post-tensioning is one promising option as it offers efficiency and geometric freedom and does not interfere with the production process. Another reinforcing procedure that shows great potential is embedding continuous carbon or glass fibres during the printing process. To date, combining these two methods with short-fibre concrete presents the most viable solution. Prefabrication and modular construction is another possible avenue. Off-site manufacturing of building components and modules offers advantages in terms of quality control, reduced construction time, and minimized waste generation. At the same time, the design of modules that are structurally efficient, transportable, easily assembled and meeting building code requirements presents a great challenge, especially for complex architectural designs. The transportation and handling of prefabricated modules constraint their dimensions and limit options for the volumetric modular construction. Connection and assembly are other challenges associated with this construction method. Over the last decade, the research and development of steel modular connections have produced several types of innovative connection systems and steel modular structures (see Section 4.2). The ongoing research is currently focusing on improving the seismic performance of these systems. The concrete modular systems though have been lacking research attention. The current precast concrete practice makes use of wet joints involving cast-in-place concreting, which requires formwork installation and takes time to cure. One way to overcome this limitation is to use the mortarless topological interlocking assemblies. Among the advantages of these assemblies are elevated toughness and energy absorption ability.