Concrete in an AM process

Abstract

This thesis examines the additive manufacturing (AM) of concrete, its possibilities, feasibility and advantages over existing techniques. The first part generally focuses on the characteristic properties of concrete that are important and how they relate to an AM method, for instance aggregates and reinforcement. After this extensive introduction in the field of concrete and AM, the current situation regarding additive manufacturing of concrete is described. On the basis of literature resulting products are shown and discussed. Their characteristics are compared to detect a match or mismatch between the AM technique and the produced elements. The outcome of this evaluation is used to describe improvements which are elaborated in the second part. This design part consists of a roadmap that shows a future vision. Concrete is a new material in the field of additive manufacturing. Since it is one of the materials that hardens by a chemical reaction, considerable attention needs to be paid to the workability of it in an AM process. Traditional processing techniques are adapted to these characteristics but concrete does not let itself dictate how to behave. The roadmap envisions how the technique has to evolve in order to implement the characteristic properties of concrete. The possibilities for products made with an additive process are endless, but just replacing existing production methods with additive ones is impossible. Although improved freeform production techniques are still the aim of this research, this does not mean that more freedom in form is by definition the largest improvement that AM can offer at the moment. From another point of view the implementation of additional functions in traditional products can be of great value. Product ideas and an evaluation of the techniques shown in the vision are related to the developments to achieve an increase in speed, surface quality and strength in the AM production technique, next to the requirements that have to be set regarding a matching fresh concrete mixture. These essential aspects of the process lead to the important conclusion that in the AM of concrete, both material and production technique have to be matched precisely. Next to matching process and material it is important to match process and product. Concrete is widely used and not all products should be made using an AM process. Simply copying standardized elements does not add the added value layered fabrication methods can achieve if used adequately.