**7.6 3D printing**

3D printing is an additive manufacturing process for making 3D solid objects from a digital file. The materials used to produce the object are various types of concrete, hard plastic, carbon fibre, metal, etc. The use of 3D printing has developed in the latest years with technological advances in the engineering sector [23]. 3D printing engineering models are becoming an interesting alternative. Architectural models are commonly made of wood, cardboard, plastic or other mouldable materials. Architects need models to study aspects of their design. It is all the time, modified to obtain an accurate concept of their idea in architectural design. 3D printing at a construction scale will have a wide diversity of applications within the AEC sector. The major advantages of these technologies include speeding up the construction process, reducing labour cost, increasing accuracy, decreasing complexity, greater job integration and reducing waste produced. A variety of different approaches have been demonstrated yet, which include on-site and off-site manufacturing of buildings and building components, using industrial robots, tethered autonomous vehicles and gantry systems [24].

Demonstrations of construction 3D printing technologies to date have included the fabrication of housing, building construction components (cladding, structural panels, and columns), bridges, civil infrastructure, artificial reefs, follies and

sculptures. It may also allow construction to be carried out in harsh or hazardous environments that are unsuitable for human workforce such as places with special conditions [25].
