Additive Fabrication of Concrete Elements by Robots (2020-09)¶

For the last 150 years, engineers and designers have been choosing reinforced concrete as the material to use for load bearing structures. Over the decades it has proven itself as a robust composite material. It is versatile and has insulating and fire proofing properties. Reinforced concrete has become indispensable as a building material, both for the elements which come in contact with the ground and for the structural elements which transfer horizontal or vertical loads. Concrete is not only used in multi-storey buildings but also applied in infrastructure. Over the course of time, two production processes have established themselves, in-situ concrete construction and prefabricated construction. The latter can be further divided into fully precast elements and elements that are completed once they have been filled with in-situ concrete. Over the years, the cost of producing concrete elements has shifted between material and labour costs and this has effected the appearance of concrete constructions. Originally, the cost of the materials was high and the labour costs low and this led to lean, filigree designs. Nowadays, however, to save on the expensive labour costs and make use of the cheap material costs, bulky, thick walled components are very common. This development is also accompanied by the demands of recent building standards which include, for example, the necessary concrete cover for durable components. Fundamentally and above all else, there is an enormous demand for building materials due to current urbanisation trends and this, in turn, pushes us to rethink material efficiency. This is especially necessary as there are a large number of multi-storey buildings being built where the efficiency of the structure is ignored. They are responsible for a large amount of the building materials being used. In the light of the fact that the production of cement for reinforced concrete accounts for about 5% of global man-made CO2 annually (Worrell et al., 2001), t he question may be asked whether the way in which our reinforced concrete structures are built is in need of urgent review and revision. Although the composite material has seen many changes and improvements over the years in the area of concrete’s properties, rebar manipulation and formwork production, one thing has barely changed and that is the pouring of the concrete. This article presents the research project COEBRO which dealt with using concrete printing to produce an alternative to a poured flat slab ceiling (Fig. 1).