This graduation project is in cooperation with TU Delft, Tentech BV, Aectual and White Lioness technologies. It aims to investigate the feasibility of using recycled plastics as material for large-scale 3D printing with the 3D printer KamerMaker. In the meantime, a thickness distribution methodology is proposed for taking advantage of the flexibility of the 3D printing technology to optimise the printed structure, especially as moulds for casting concrete, to increase the structural efficiency. The content of the project contains laboratory tests, numerical modelling, design methodology and a case study.

The objective of this research project is to verify whether 3D printing of concrete (3DPC) reduces the environmental impact by increasing the structural efficiency. During the literature study, numerous articles were identified that claimed an increase of structural efficiency by using 3DPC to reduce material use. Some of these articles suggest that an increase in structural efficiency results in a reduction of environmental impact. However, these articles do not support this potential with a research study.

This research project therefore studies the relation between structural efficiency and the environmental impact of a 3DPC bridge. This relation is studied by developing a design model that calculates structural efficiency and determines the environmental impact. The design model is developed in a visual script environment for parametrically controlling visual design software. The parametric script specifies and combines information in an XML file used for structural analysis in finite element software. This analysis is executed on command in the parametric environment and the results are used for verifying the structural safety. The structural safety is expressed in a material utilisation ratio. This ratio indicates the used proportion of strength of the material and can be used as an indicator for structural efficiency. After calculating the structural efficiency, the design model is used to determine the environmental impact of the structure expressed in shadow costs. Shadow costs quantify the environmental impact of materials and processes related to geometric quantities defined in the design model.

Multiple combinations of parameters have been compared to determine the relation between structural efficiency and environmental impact. The results of the comparison show that an increase in structural efficiency results in decreased material use. A decrease in material use reduces the environmental impact because ±59% of the impact is related to 3DPC material. The environmental impact of the 3DPC bridge is then compared to a hollow-core-slab element with a similar functionality to verify the claimed potential. This comparison shows that the environmental impact of 3DPC is almost two times higher than the compared conventional method.

Therefore, using a novel design model and based on the results, following two conclusions can be drawn:
1. Increasing structural efficiency can decrease the environmental impact of a 3DPC bridge, and
2. Considering the state of 3D printing concrete technology at present, applications of this technology for bridges can result in a higher environmental impact than the compared conventional method.