BeXTRUS

Concrete 3D printing (Impression 3D de Bétons par eXTRUSion)

The primary objective of the BEXTRUS project is to develop concrete compositions that can be printed by extrusion. This requires formulations that are fluid enough to be pumpable and extrudable but also firm enough to be buildable. These characteristics call on the conflicting rheological properties of concrete.

This is the complexity of this first objective. In order to reduce the risk involved in achieving this objective and the final deliverable of the project, only two formulations are targeted: one corresponding to an application in civil engineering and another corresponding to an application in refractory concretes. A single type of binder as well as conventional raw materials for aggregates and fine particles will be considered for each of the applications.

The second objective is to create 3D demonstrators of complex shapes using the formulations developed. The aim is to produce simple shapes by adjusting the machine parameters (pumping power, flow rate, size of extrusion screws, etc.) in such a way that the simple printed shape meets the initial specifications: a stack of adherent layers with no discontinuity at the extruded bead, little or no deformation of the lower layers under the effect of the weight of the upper layers. After this stage, complex geometries will be printed. The part designs will meet industrial requirements, as they will be the result of consultation with the industrial steering committee.

At the same time, characterization tests will be carried out on fresh, hardened and cured (refractory) concrete. The results of these tests, coupled with numerical modelling, will be used to minimize the development time for new formulations and also to help establish a protocol for extrusion printing of 3D concrete parts.